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Page No 23:

Question 1:

Which is the basic requirement of living organisms for obtaining energy?

Answer:

Food is the basic requirement of all living organisms for obtaining energy.

Page No 23:

Question 2:

Which of the following type of energy is used by living organisms to perform vital life processes? Kinetic energy, Chemical energy, Potential energy, Nuclear energy

Answer:

Chemical energy is used by the living organisms to perform their vital life processes.

Page No 23:

Question 3:

Which of the following is an autotroph?
Green plant or Man

Answer:

Green plant is an autotroph as it can prepare its own food.

Page No 23:

Question 4:

Name two inorganic substances which are used by autotrophs to make food.

Answer:

Carbon dioxide and water are the two inorganic substances used by autotrophs to make their food.

Page No 23:

Question 5:

What is the mode of nutrition in fungi?

Answer:

Some fungi are parasitic while most exhibit saprotrophic mode of nutrition.

Page No 23:

Question 6:

Name one organism each having saprophytic, parasitic and holozoic modes of nutrition.

Answer:

Mushrooms have saprophytic mode of nutrition, Cascuta and mistletoe have parasitic mode of nutrition and human beings have holozoic mode of nutrition.

Page No 23:

Question 7:

Name the process by which plants make food.

Answer:

The process by which plants make food is known as photosynthesis.



Page No 24:

Question 8:

In addition to carbon dioxide and water, state two other conditions necessary for the process of photosynthesis to take place.

Answer:

Presence of sunlight and the green pigment, chlorophyll are the two other conditions necessary for the process of photosynthesis.

Page No 24:

Question 9:

Apart from sunlight and chlorophyll, what other things are required to make food by photosynthesis?

Answer:

Apart from sunlight and chlorophyll, carbon dioxide and water are also required to make food by photosynthesis.

Page No 24:

Question 10:

(a) Name a gas used in photosynthesis.
(b) Name a gas produced in photosynthesis.

Answer:

(a) Carbon dioxide is used in photosynthesis.
(b) Oxygen is produced in photosynthesis.

Page No 24:

Question 11:

The leaves of a plant first prepare food A by photosynthesis. Food A then gets converted into food B. What are A and B?

Answer:

Food A is glucose and food B is starch.

Page No 24:

Question 12:

Which substance is used to remove chlorophyll from a green leaf during photosynthesis experiments?

Answer:

Alcohol is used to remove chlorophyll from a green leaf during photosynthesis experiments.

Page No 24:

Question 13:

Why do we boil the leaf in alcohol when we are testing it for starch?

Answer:

We boil the leaf in alcohol when we are testing it for starch to remove the chlorophyll from it and decolourise it.

Page No 24:

Question 14:

(a) Name the pigment in leaves which absorbs sunlight energy.
(b) What is the colour of this pigment?

Answer:

(a) In leaves, the pigment that absorbs the energy of sunlight is chlorophyll.
(b) This pigment is green in colour.

Page No 24:

Question 15:

Name the pigment which can absorb solar energy.

Answer:

The pigment that can absorb solar energy is chlorophyll.

Page No 24:

Question 16:

Name the organelle of plant cells in which photosynthesis occurs.

Answer:

Chloroplast is the organelle of plant cells where photosynthesis takes place.

Page No 24:

Question 17:

Apart from carbon dioxide and water, name four other raw materials which are needed by the plants.

Answer:

Apart from carbon dioxide and water, plants require nitrogen, phosphorus, iron and magnesium.

Page No 24:

Question 18:

Where is chlorophyll mainly present in a plant?

Answer:

Chlorophyll is mainly present in the chloroplasts, which are present in the photosynthetic cells of green plants.

Page No 24:

Question 19:

What is the name of those cells in the leaf of a plant which control the opening and closing of stomata?

Answer:

Guard cells control the opening and closing of stomata.

Page No 24:

Question 20:

Name an animal whose process of obtaining food is called phagocytosis.

Answer:

Amoeba is an organism whose process of obtaining food is called phagocytosis.

Page No 24:

Question 21:

All the animals can be divided into three groups on the basis of their eating habits. Name the three groups.

Answer:

On the basis of their eating habits, animals are divided into herbivores, carnivores and omnivores.

Page No 24:

Question 22:

What is the scientific name of the animals which are:
(i) only meat eaters?
(ii) only plant eaters?
(iii) both, plant and meat eaters?

Answer:

(i) Carnivores are only meat eaters.
(ii) Herbivores are only plant eaters.
(iii) Omnivores are both plant and meat eaters.

Page No 24:

Question 23:

Name the green pigment present in the leaves of a plant.

Answer:

Chlorophyll is the green pigment present in the leaves of a plant.

Page No 24:

Question 24:

Arrange the following processes involved in the nutrition in animals in the correct order (in which they take place):
Assimilation, Egestion, Ingestion, Absorption, Digestion

Answer:

The correct order of the processes involved in the nutrition of animals is given below:

Ingestion  Digestion  Absorption  Assimilation Egestion

Page No 24:

Question 25:

How does Amoeba engulf the food particle?

Answer:

Amoeba engulfs the food particle by forming finger-like projections around it, which are known as pseudopodia.

Page No 24:

Question 26:

What substances enter into the food vacuole in Amoeba to break down the food?

Answer:

Digestive enzymes enter into the food vacuole in Amoeba to break down the food.

Page No 24:

Question 27:

From which part of the body, undigested food is egested in Amoeba?

Answer:

Undigested food is egested through the cell membrane in an Amoeba .

Page No 24:

Question 28:

Name a unicellular animal which uses cilia to move food particles into its mouth.

Answer:

Paramecium uses cilia to move food particles into its mouth.

Page No 24:

Question 29:

Name the enzyme present in human saliva. What type of food material is digested by this enzyme?

Answer:

Salivary amylase is present in human saliva. Starch is partially digested by this enzyme.

Page No 24:

Question 30:

Which of the organs perform the following functions in humans?
(i) Absorption of food
(ii) Absorption of water

Answer:

(i) Small intestine
(ii) Large intestine

Page No 24:

Question 31:

What moves the food in the digestive organs?

Answer:

Food moves in the digestive organs through peristaltic movement.

Page No 24:

Question 32:

What is the other name of food pipe?

Answer:

Food pipe is also known as oesophagus.

Page No 24:

Question 33:

What substance is mixed with food in the mouth during chewing by the teeth?

Answer:

When we chew our food, saliva gets mixed with food in the mouth.

Page No 24:

Question 34:

What is the name of tiny projections on the inner surface of small intestine which help in absorbing the digested food?

Answer:

The tiny projections on the inner surface of the small intestine that help in absorbing the digested food are known as villi.

Page No 24:

Question 35:

In which part of the digestive system is water absorbed?

Answer:

Water is absorbed in the large intestine.

Page No 24:

Question 36:

What is the name of the opening in the human body though which undigested food is thrown out?

Answer:

The opening in the human body through which the undigested food is thrown out is known as anus.

Page No 24:

Question 37:

Where is digested food absorbed into blood in human body?

Answer:

In the human body, the digested food is absorbed into the blood in the small intestine.

Page No 24:

Question 38:

Name the biological catalysts which bring about chemical digestion of food.

Answer:

Enzymes are the biological catalysts that bring about the chemical digestion of food.

Page No 24:

Question 39:

Fill in the following blanks with suitable words :
(a) All green plants are ....................
(b) All non-green plants and animals are ....................
(c) Heterotrophs depend on .................... and other .................... for food.
(d) Green plants use .................... and .................... to make food.
(d) Iodine turns blue-black on reacting with ....................

Answer:

(a) All green plants are autotrophs.
(b) All non-green plants and animals are heterotrophs.
(c) Heterotrophs depend on autotrophs and other heterotrophs for food.
(d) Green plants use carbon dioxide and water to make food.
(e) Iodine turns blue-black on reacting with starch.



Page No 25:

Question 40:

(a) what is chlorophyll? What part does chlorophyll play in photosynthesis?
(b) (i) Which simple food is prepared first in the process of photosynthesis?
(ii) Name the food which gets stored in plant leaves.

Answer:

(a) Chlorophyll is the green pigment present in the chloroplasts of the cells of green plants. It absorbs sunlight for photosynthesis.

(b) (i) In the process of photosynthesis, glucose is prepared first.
(ii) Starch is stored in plant leaves.

Page No 25:

Question 41:

(a) What criteria can be used to decide whether something is alive?
(b) What is meant by life processes? Name the basic life processes common to all living organisms which are essential for maintaining life.

Answer:

(a) Movement is the criteria used to decide whether something is alive.

(b) The basic functions performed by the living organisms to maintain their life on the Earth are known as life processes. The basic life processes common to all living organisms and essential for maintaining life are nutrition, growth, movement, respiration, transportation, reproduction, excretion and control and coordination.

Page No 25:

Question 42:

(a) What are autotrophs? Give one example of autotrophs.
(b) What are the conditions necessary for autotrophic nutrition?

Answer:

(a) The organisms that prepare their food themselves are known as autotrophs. Green plants are autotrophs.

(b) The presence of chlorophyll, carbon dioxide, water and sunlight are the conditions necessary for autotrophic nutrition.

Page No 25:

Question 43:

(a) What are heterotrophs? Give one example of heterotrophs.
(b) What is the difference between autotrophic nutrition and heterotrophic nutrition?

Answer:

(a) Organisms that depend upon autotrophs and other heterotrophs for their food are known as heterotrophs. Animals are heterotrophs.

(b)

Autotrophic nutrition Heterotrophic nutrition
The mode of nutrition in which an organism prepares its own food with the help of simple inorganic materials like water and carbon dioxide from the surroundings is known as autotrophic nutrition. The mode of nutrition in which an organism cannot prepare its own food and depend upon other organisms for its food is known as heterotrophic nutrition.

Page No 25:

Question 44:

(a) Define a nutrient. Name four important nutrients present in our food.
(b) What are the various types of heterotrophic nutrition?

Answer:

(a) A nutrient is an organic or inorganic substance required for the maintenance of life and survival of the living organisms. Four important nutrients present in our food are carbohydrates, proteins, vitamins and fats.

(b) The various types of heterotrophic nutrition are saprophytic, parasitic and holozoic nutrition.

Page No 25:

Question 45:

(a) Photosynthesis converts energy X into energy Y. What are X and Y?
(b) State the various steps involved in the process of photosynthesis.

Answer:

(a) X is solar energy and Y is chemical energy.

(b) The various steps involved in the process of photosynthesis are:-

  • Absorption of solar energy by the chlorophyll
  • Splitting of water into hydrogen and oxygen by this light energy
  • Conversion of solar energy into chemical energy
  • Reduction of carbon dioxide to form glucose by the transformed chemical energy

Page No 25:

Question 46:

(a) How do plants obtain food?
(b) Why do plants need nitrogen? How do plants obtain nitrogen?

Answer:

(a) Plants prepare their own food in the presence of sunlight and chlorophyll. This is done by converting simple inorganic materials like carbon dioxide and water present in the surroundings.

(b) Plants need nitrogen for making proteins and other compounds. Plants obtain nitrogen from the soil.

Page No 25:

Question 47:

Define (i) saprophytic nutrition (ii) parasitic nutrition, and (iii) holozoic nutrition. Give one example of each type.

Answer:

(i) The mode of nutrition in which the organisms depend upon dead and decaying plants, animals and organic materials for obtaining their nutrition is known as saprophytic nutrition. Example: Fungi

(ii) The mode of nutrition in which an organism derives its nutrition from the body of other living organisms is known as parasitic nutrition. Example: Cuscuta

(iii) The mode of nutrition in which an organism takes in the complex organic food material into its body by the process of ingestion, followed by digestion and then absorption of food in the body cells is known as holozoic nutrition. Example: Human beings

Page No 25:

Question 48:

Define (i) saprophyte, and (ii) parasite. Name two saprophytes and two parasites.

Answer:

(i) Organisms that obtain their nutrition from dead and decaying plants, animals or organic matter are known as saprophytes. Two saprophytes are mushroom and bread mould.

(ii) Organisms that feed on other living organisms, called hosts, are known as parasites.
     Two parasites are Cuscuta and Plasmodium.

Page No 25:

Question 49:

(a) How does carbon dioxide from the air enter the leaves of a plant to be used in photosynthesis?
(b) How does water from the soil reach the leaves of a plant to be used in photosynthesis?

Answer:

(a) Carbon dioxide from the air enters the leaves of a plant through tiny pores present on the lower surface of the leaves called stomata.
(b) Water is absorbed from the soil by the root hairs present in the roots of the plants through the process of osmosis.

Page No 25:

Question 50:

What substances are contained in gastric juice? What are their functions?

Answer:

The gastric juice contains hydrochloric acid, pepsin enzyme and mucus. Their functions are as follows:-
1) Hydrochloric acid: It creates an acidic environment for the action of pepsin as well as kills the bacteria present in the food.
2) Pepsin: It begins the digestion of proteins into smaller molecules.
3) Mucus: It protects the stomach wall from hydrochloric acid.

Page No 25:

Question 51:

What substances are contained in pancreatic juice? What are their functions?

Answer:

Pancreatic juice contains digestive enzymes such as amylase, trypsin and lipase.
Following are the functions of these substances:
(a) Amylase breaks down the starch.
(b) Trypsin digests the proteins.
(c) Lipase breaks down the emulsified fats.

Page No 25:

Question 52:

(a) What is the role of hydrochloric acid in our stomach?
(b) What is the function of enzymes in the human digestive system?

Answer:

(a) In our stomach, the role of hydrochloric acid is to create an acidic condition by making the gastric juice acidic.

(b) The function of enzymes in the human digestive system is to digest the complex food substances like starch, proteins and fats into simple molecules.

Page No 25:

Question 53:

(a) Which part of the body secretes bile? Where is bile stored? What is the function of bile?
(b) What is trypsin? What is its function?

Answer:

(a) Bile is secreted by liver. It is stored in the gall bladder and helps in the digestion of fats. Also, it converts the acidic food into alkaline.

(b) Trypsin is an enzyme present in the digestive juice secreted by the pancreas. Its function is to digest the proteins.

Page No 25:

Question 54:

What are the functions of liver and pancreas in the human digestive system ?

Answer:

Liver secretes bile, which helps in making the acidic food alkaline. Also, it digests fats. Pancreas secretes the digestive juice containing three enzymes, i.e. amylase, trypsin and lipase. Amylase digests starch; trypsin digests proteins and lipase digests fats.

Page No 25:

Question 55:

Match the organisms given in column I with the processes given in column II:

  Column I   Column II
(i) Leech (a) Holozoic nutrition
(ii) Amoeba (b) Autotrophic nutrition
(iii) Mushroom (c) Parasitic nutrition
(iv) Green plant (d) Saprophytic nutrition

Answer:

Column I Column II
(i) Leech (c) Parasitic nutrition
(ii) Amoeba (a) Holozoic nutrition
(iii) Mushroom (d) Saprophytic nutrition
(iv) Green plant (b) Autotrophic nutrition

Page No 25:

Question 56:

Name the following :
(a) The process in plants which converts light energy into chemical energy.
(b) Organisms that cannot prepare their own food.
(c) Organisms that can prepare their own food.
(d) The cell organelle where photosynthesis occurs.
(e) The cells which surround a stomatal pore.
(f) An enzyme secreted by gastric glands in stomach which acts on proteins.

Answer:

(a) Photosynthesis is the process in plants that converts light energy into chemical energy.
(b) Heterotrophs cannot prepare their own food.
(c) Autotrophs can prepare their own food.
(d) Chloroplast is the cell organelle where photosynthesis takes place.
(e) Guard cells surround a stomatal pore.
(f) Pepsin is an enzyme secreted by the gastric glands in the stomach. It acts on proteins.

Page No 25:

Question 57:

Match the terms in column I with those in column II :

  Column I   Column II
(i) Trypsin (a) Liver
(ii) Amylase (b) Gastric glands
(iii) Bile (c) Pancreas
(iv) Pepsin (d) Saliva

Answer:

Column I Column II
(i) Trypsin (c) Pancreas
(ii) Amylase (d) Saliva
(iii) Bile (a) Liver
(iv) Pepsin (b) Gastric glands



Page No 26:

Question 58:

(a) What is common for Cuscuta, ticks and leeches?
(b) Name the substances on which the following enzymes act in the human digestive system:
(i) Trypsin
(ii) Amylase
(iii) Pepsin
(iv) Lipase
(c) Why does absorption of digested food occur mainly in the small intestine?

Answer:

(a) In Cuscuta, ticks and leeches, the mode of nutrition is parasitic.

(b) (i) Trypsin acts on proteins.
(ii) Amylase acts on starch.
(iii) Pepsin acts on proteins.
(iv) Lipase acts on emulsified fat.

(c) Absorption of digested food occurs mainly in the small intestine because it consist of many finger-like projections called villi that are supplied with numerous blood vessels. They provide a large surface area for the absorption of food.

Page No 26:

Question 59:

(a) Why is small intestine in herbivores longer than in carnivores?
(b) What will happen if mucus is not secreted by the gastric glands?
(c) What causes movement of food inside the alimentary canal?

Answer:

(a) Herbivores depend on plants for their nutrition. These plants contain complex carbohydrates like cellulose and hemicellulose that need to be broken down, whereas carnivores do not eat plants. Hence, small intestine is longer in herbivores than in carnivores.

(b) Mucus protects the stomach wall from hydrochloric acid. If mucus is not secreted by the gastric glands then the stomach wall will be destroyed by the acid.

(c) Peristalsis causes the movement of food inside the alimentary canal.

Page No 26:

Question 60:

(a) How do guard cells regulate opening and closing of stomatel pores?
(b) Two similar green plants are kept separately in oxygen free containers, one in dark and the other in continuous light. Which one will live longer? Give reasons.

Answer:

(a) When water flows into the guard cells, they swell and become curved. This causes the stomatal pore to open. On the other hand, when the guard cells lose water, they shrink and this cause the pore to close.

(b) The plant kept in continuous light will live longer as the leaves of the plants will be able to make food for the plant through photosynthesis. However, in the absence of light, the leaves will not be able to make food. This is because photosynthesis will not take place in the absence of light. Hence, the plant kept in dark will live shorter as compared to the plant kept in light.

Page No 26:

Question 61:

(a) What would happen if all the green plants disappear from the earth?
(b) If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer.

Answer:

(a) Green plants provide food and oxygen to all other living organisms. If they disappear from the Earth, all other organisms will die due to starvation and lack of oxygen for respiration.

(b) No, it does not mean that photosynthesis is not taking place. During the day, carbon dioxide released by plants during respiration is used up for photosynthesis, and some of the oxygen released during photosynthesis is used for respiration by the plants. Release of oxygen is a sign that photosynthesis is occurring in plant.

Page No 26:

Question 62:

(a) Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reason for your answer.
(b) What will happen to the rate of photosynthesis on a plant under the following circumstances?
(i) cloudy day in morning but bright sunshine in the afternoon
(ii) no rainfall in the area for a considerable time.
(iii) gathering of dust on the leaves

Answer:

(a) If leaves of a healthy potted plant were coated with vaseline, it will not remain healthy for long. Due to the coating of vaseline, the stomatal pores will be blocked. Hence, the plant will not be able to get oxygen for respiration and carbon dioxide for photosynthesis. Transpiration will also stop and the plant will ultimately die.

(b)  The rate of photosynthesis will:
(i) first decrease as there will be less sunlight and then increase during the afternoon
(ii) decrease due to less availability of water
(iii) decrease due to the closed stomatal pores

Page No 26:

Question 63:

(a) What is photosynthesis?
(b) Write a chemical equation to show the process of photosynthesis in plants.
(c) Explain the mechanism of photosynthesis.

Answer:

(a) The process by which green plants use sunlight to make their own food from carbon dioxide and water is known as photosynthesis. This is done in the presence of chlorophyll.

(b) Following chemical equation shows the process of photosynthesis in plants:

        6CO2     +    6H2In the presence of sunlightChlorophyll  C6H12O6  +  6O2
Carbon dioxide     Water                             Glucose     Oxygen
                  
(c)  In green plants, photosynthesis occurs in the green plastids present in the leaves and other green parts of the plant called chloroplast. The raw materials for photosynthesis, namely carbon dioxide (enters through stomata) and water (absorbed from the soil by root hair) reach the leaves. In the leaves, the chlorophyll pigment absorbs the sunlight. This solar energy is used to combine water and carbon dioxide to form glucose and oxygen. In this way, green plants convert solar energy into chemical energy by forming carbohydrates.

Page No 26:

Question 64:

(a) Name the raw materials required for photosynthesis. How do plants obtain these raw materials?
(b) What are the various conditions necessary for photosynthesis?
(c) Name the various factors which affect the rate of photosynthesis in plants.

Answer:

(a) The raw materials required for photosynthesis are water and carbon dioxide. Plants obtain water from the soil through roots and carbon dioxide from the atmosphere through stomata.

(b) Following are the conditions necessary for photosynthesis:

  • Sunlight
  • Chlorophyll
  • Carbon dioxide
  • Water
(c) Following are the factors that affect the rate of photosynthesis:
  • Appropriate sunlight
  • Water availability
  • Availability of carbon dioxide

Page No 26:

Question 65:

(a) Define nutrition. Why is nutrition necessary for an organism?
(b) What are the different modes of nutrition? Explain with one example of each mode of nutrition.
(c) Name the mode of nutrition in (i) roundworm, and (ii) Plasmodium.

Answer:

(a) The process of intake and utilisation of nutrients like carbohydrates, proteins, vitamins and fats by an organism is known as nutrition. Nutrition is necessary for an organism because it provides it with the appropriate amount of nutrients that are needed for the maintenance of life and survival.

(b) Following are the different modes of nutrition:
(i) Autotrophic nutrition: 
It is the mode of nutrition in which an organism makes its own food by the process of photosynthesis. Green plants are autotrophs.
(ii) Heterotrophic nutrition:
It is the mode of nutrition in which an organism obtains its food from the autotrophs or other heterotrophs. All animals are heterotrophs.

(c) The mode of nutrition in a (i) roundworm and a (ii) Plasmodium is parasitic.

Page No 26:

Question 66:

(a) What are herbivores, carnivores and omnivores? Give two examples of each.
(b) Classify the following into herbivores, carnivores and omnivores:
Lion, Man, dog, Goat, Crow, Elephant, Snake, Hawk, Rabbit, Deer
(c) Name the five steps which occur in the process of nutrition in animals.

Answer:

(a) Animals that eat plants for their nutrition are called herbivores. For example: Cows and goats
Animals that eat flesh of other animals are called carnivores. For example: Lions and tigers
Animals that eat both plants and animals are called omnivores. For example: Human beings and bears

(b) Goats, elephants, rabbits and deer are herbivores.
Lions, snakes and hawks are carnivores.
Men, crows and dogs are omnivores.

(c) Following are the five steps that occur in the process of nutrition in animals:

  • Ingestion
  • Digestion
  • Absorption
  • Assimilation
  • Egestion

Page No 26:

Question 67:

(a) Describe the process of nutrition in Amoeba. Draw labelled diagrams to show the various steps in the nutrition in Amoeba.
(b) What is the mode of nutrition in Amoeba known as?
(c) What is the process of obtaining food by Amoeba called? What does it mean?

Answer:

(a) Following are the steps involved in the nutrition in Amoeba:
(i) Ingestion: Amoeba ingests food along with a little amount of the surrounding water. It does this using its pseudopodia and forms a food vacuole.
(ii) Digestion: The food in the food vacuole is digested by the digestive enzymes that enter from the cytoplasm.
(iii) Absorption: The digested food is directly absorbed in the cytoplasm of the Amoeba cell by diffusion.
(iv) Assimilation: Some part of the digested food is used for acquiring energy for various life processes. This is done through respiration.
(v) Egestion: The undigested food is thrown out of the body through the cell membrane.


(b) An Amoeba has holozoic mode of nutrition.

(c) The process of obtaining food by Amoeba is called phagocytosis. It means cell feeding.




 

Page No 26:

Question 68:

(a) Draw a labelled diagram of the human digestive system. With the help of this diagram, describe the process of digestion of food in man (humans).
(b) Describe one way in which the small intestine is adapted for the absorption of digested food.
(c) What is the special name of the contraction and expansion movement which pushes the food further in our digestive tract (or alimentary canal)?

Answer:

(a)


Following is the process of digestion of food in a human being:

(i) Digestion in mouth: Digestion of food starts in the mouth. Here, the food is cut into small pieces by the teeth. The saliva produced by the salivary glands is mixed with the food by the tongue. The saliva contains the enzyme salivary amylase, which digests the starch and breaks it into sugar.
(ii) Digestion in stomach: The food then passes through the oesophagus and reaches the stomach. The walls of stomach release hydrochloric acid, mucous and the enzyme pepsin. HCl creates an acidic environment in the stomach, pepsin digests proteins and mucous prevents the stomach wall from erosion.
(iii) Digestion in small intestine: The partially digested food enters the small intestine. Small intestine receives secretions from liver and pancreas. Liver secrets bile, which helps in making the food alkaline and also breaks the fats. Pancreas secrete three enzymes, which are trypsin, amylase and lipase. Trypsin digests proteins, amylase digests starch and lipase digests fats.
 The intestinal juice secreted by small intestine completes the digestion of starch into glucose, proteins into amino acids and fats into fatty acid and glycerol.

(b) Small intestine has many tiny finger like projections in their inner walls, which are called villi. These increase the surface area for rapid absorption of the digested food, making the small intestine well-adapted for absorption.

(c) Peristalsis is the special name of the contraction and expansion movement that pushes the food further into our digestive tract (or alimentary canal).

Page No 26:

Question 69:

(a) Describe the parts  of our tooth with the help of a labelled diagram.
(b) What is meant by dental caries? How are they caused?
(c) What is dental plaque? What harm can it do? How can the formation of plaque be prevented?

Answer:

(a)

Our tooth contains the following three parts:
(i) Enamel: It is the outer covering of the teeth. It is harder than bones. In fact, it is the hardest material in the human body.
(ii) Dentine: It is located below the enamel. It is similar to bones.
(iii) Tooth pulp: It is a pulp cavity that consists of nerves and blood vessels. It is located inside the dentine.

(b) The formation of small cavities in the teeth are known as dental caries. They are caused by acids formed by bacteria on eating sugar laden food. It is also caused by improper dental care.

(c) Dental plaque refers to a sticky, yellowish layer of food particles and bacterial cells that deposits on the teeth if they are not cleaned regularly. Dental plaque leads to tooth decay. Brushing of teeth regularly after eating food prevents the formation of plaque.

Page No 26:

Question 70:

(a) Name the main organs of the human digestive system. Also name the associated glands.
(b) How do carbohydrates, fats and proteins get digested in human beings?

Answer:

(a) The main organs of human digestive system are mouth, oesophagus, stomach, small intestine, large intestine and anus. The associated glands are salivary glands, liver and pancreas.

(b) Carbohydrates are digested by the enzyme, salivary amylase, present in the saliva. As food enters the mouth cavity, it gets mixed with the saliva, which contains salivary amylase. This enzyme helps in the digestion of starch.
The enzyme, pancreatic amylase, is secreted by the pancreas. This enzyme reaches the small intestine and digests the carbohydrates.
Proteins are digested by the enzyme, pepsin, that is secreted in the stomach by the glands presents in its walls. Trypsin is secreted by the pancreas. This enzyme reaches the small intestine and digests the proteins.
Fats are digested by the enzyme, lipase, that is secreted by the pancreas and the bile juice that is secreted by the liver. These two act on the fats in the small intestine.



Page No 27:

Question 71:

Which of the following has the longest small intestine?
(a) carnivore
(b) omnivore
(c) herbivore
(d) autotroph

Answer:

(c) herbivore
This is because herbivores mainly eat plants.
Plants contain cellulose, which is difficult to digest. Hence, they have the longest small intestine.

Page No 27:

Question 72:

The process of obtaining food by Amoeba is known as:
(a) dialysis
(b) cytokinesis
(c) phagocytosis
(d) amoebiasis

Answer:

(c) phagocytosis
Amoebae obtain food by the process called phagocytosis, which means cell feeding.

Page No 27:

Question 73:

The organism having parasitic mode of nutrition is:
(a) Penicillium
(b) Plasmodium
(c) Paramecium
(d) Parrot

Answer:

(b) Plasmodium
Plasmodium is a microbial parasite that has a parasitic mode of nutrition.

Page No 27:

Question 74:

One of the following organisms has a saprophytic mode of nutrition. This organism is:
(a) mushroom
(b) malarial parasite
(c) leech
(d) lice

Answer:

(a) mushroom
Mushroom obtains its food from decaying organic materials like rotten wood. Thus, it has a saprophytic mode of nutrition.

Page No 27:

Question 75:

The length of small intestine in a human adult is about:
(a) 4.5 m
(b) 1.5 m
(c) 3.5 m
(d) 6.5 m

Answer:

(d) 6.5 m
The length of small intestine in a human adult is around 6.5 m.

Page No 27:

Question 76:

The process of digestion of food in humans begins in:
(a) stomach
(b) food pipe
(c) mouth
(d) small intestine

Answer:

(c) mouth
The process of digestion begins in the mouth with the help of the enzymes present in the saliva.

Page No 27:

Question 77:

The process of digestion in humans is completed in:
(a) oesophagus
(b) small intestine
(c) stomach
(d) large intestine

Answer:

(b) small intestine
The digestion of food, i.e. carbohydrates, fats and proteins, completes in the small intestine.

Page No 27:

Question 78:

In human digestive system, bile is secreted by:
(a) pancreas
(b) liver
(c) kidneys
(d) stomach

Answer:

(b) Liver
Liver secretes the greenish yellow liquid called bile.

Page No 27:

Question 79:

Two of the following organisms have a holozoic mode of nutrition. These organisms are:
(a) Paramecium and Plasmodium
(b) Plasmodium and Parakeet
(c) Parakeet and Paramecium
(d) Paramecium and Parasite

Answer:

(c) Parakeet and Paramecium
Parakeet and Paramecium feed on solid food. Therefore, they have holozoic mode of nutrition.

Page No 27:

Question 80:

The autotrophic mode of nutrition requires:
(a) carbon dioxide and water
(b) chlorophyll
(c) sunlight
(d) all of the above

Answer:

(d) All of the above
In autotrophic mode of nutrition, green plants that have chlorophyll, make food from carbon dioxide and water in the presence of sunlight.

Page No 27:

Question 81:

The correct order of steps occurring in nutrition in animals is:
(a) Ingestion → Absorption → Digestion → Assimilation → Egestion
(b) Ingestion → Digestion → Assimilation → Absorption → Egestion
(c) Ingestion → Digestion → Absorption → Assimilation → Egestion
(d) Ingestion → Assimilation → Digestion → Absorption → Egestion

Answer:

(c) Ingestion → Digestion → Absorption → Assimilation → Egestion

The food is ingested through the mouth. It is then digested in the mouth, the stomach and the small intestine. Then, it is absorbed and assimilated in the small intestine, the reabsorption of water takes place in the large intestine and the undigested waste is egested through the anus.

Page No 27:

Question 82:

In human digestive system, the enzymes pepsin and trypsin are secreted respectively by:
(a) pancreas and liver
(b) stomach and salivary glands
(c) pancreas and gall bladder
(d) stomach and pancreas

Answer:

(d) stomach and pancreas
Pepsin is secreted by the stomach and trypsin is secreted by the pancreas.

Page No 27:

Question 83:

When carrying out the starch test on a leaf, why is it important to boil the leaf in alcohol?
(a) to dissolve the waxy cuticle
(b) to make the cells more permeable to iodine solution
(c) to remove the chlorophyll
(d) to stop chemical reactions in the cells.

Answer:

(c) to remove the chlorophyll
When carrying out the starch test, it is important to remove the chlorophyll by boiling the leaf in alcohol. This is done because the green colour of the chlorophyll interferes with the iodine test.

Page No 27:

Question 84:

Pancreatic juice contains enzymes which digest:
(a) proteins and carbohydrates only
(b) proteins and fats only
(c) fats and carbohydrates only
(d) proteins, fats and carbohydrates

Answer:

(d) proteins, fats and carbohydrates
Pancreatic juice has the enzymes amylase for the digestion of carbohydrates, trypsin for the digestion of proteins and lipase for the digestion of emulsified fats.

Page No 27:

Question 85:

Which of the following is the correct statement regarding bile?
(a) secreted by bile duct and stores in liver
(b) secreted by gall bladder and stored in liver
(c) secreted by liver and stored in bile duct
(d) secreted by liver and stored in gall bladder

Answer:

(d) secreted by liver and stored in gall bladder
Bile is secreted by the liver and stored in the gall bladder till required.

Page No 27:

Question 86:

Where are proteins first digested in the alimentary canal?
(a) small intestine
(b) oesophagus
(c) mouth
(d) stomach

Answer:

(d) stomach
The digestion of proteins begins in the stomach by pepsin.

Page No 27:

Question 87:

The inner lining of stomach is protected by one of the following from the harmful effect of hydrochloric acid. This is:
(a) pepsin
(b) mucus
(c) saliva
(d) bile

Answer:

(b) mucus
Mucus protects the inner lining of the stomach from erosion, which can be caused by hydrochloric acid.

Page No 27:

Question 88:

Which part of alimentary canal receives bile from the liver?
(a) oesophagus
(b) small intestine
(c) stomach
(d) large intestine

Answer:

(b) small intestine
Small intestine receives bile from the liver, which is temporarily stored in the gall bladder.

Page No 27:

Question 89:

Which of the following component of our food is digested by an enzyme which is present in saliva as well as in pancreatic juice?
(a) proteins
(b) fat
(c) minerals
(d) carbohydrate

Answer:

(d) carbohydrate
Carbohydrates are digested by amylases that are present in the saliva and the pancreatic juice.



Page No 28:

Question 90:

If the saliva is lacking in salivary amylase, then which of the following processes taking place in the buccal cavity will be affected?
(a) proteins breaking down into amino acids
(b) starch breaking down into sugars
(c) fats breaking down into fatty acids and glycerol
(d) intestinal layer breaking down leading to ulcers

Answer:

(b) starch breaking down into sugars
Salivary amylase digests carbohydrates. Starch is a carbohydrate, which is digested and broken down into sugars by the salivary amylase in the buccal cavity.

Page No 28:

Question 91:

Which of the following are the correct functions of two components of pancreatic juice trypsin and lipase?
(a) trypsin digests proteins and lipase carbohydrates
(b) trypsin digests emulsified fats and lipase proteins
(c) trypsin digests starch and lipase fats
(d) trypsin digests proteins and lipase emulsified fats

Answer:

(d) trypsin digests proteins and lipase emulsified fats
Trypsin and lipase are enzymes present in the pancreatic juice that digest proteins and emulsified fats, respectively.

Page No 28:

Question 92:

The oxygen liberated during photosynthesis by green plants comes from:
(a) glucose
(b) water
(c) carbon dioxide
(d) chlorophyll

Answer:

(b) water
During photosynthesis, the water molecule is split into hydrogen and oxygen.

Page No 28:

Question 93:

Which of the following is an incorrect statement?
(a) energy is essential for life processes
(b) organisms grow with time
(c) movement of molecules does not take place among cells
(d) organisms must repair and maintain their body

Answer:

(c) movement of molecules does not take place among cells
Movement of molecules takes place among cells.

Page No 28:

Question 94:

The internal energy (cellular energy) reserve in autotrophs is:
(a) proteins
(b) fatty acids
(c) glycogen
(d) starch

Answer:

(d) Starch
The autotrophs, like plants, store energy in the form of starch.

Page No 28:

Question 95:

Which of the following events does not occur in photosynthesis?
(a) conversion of light energy into chemical energy
(b) reduction of carbon dioxide to carbohydrates
(c) oxidation of carbon to carbon dioxide
(d) absorption of light energy by chlorophyll

Answer:

(c) oxidation of carbon to carbon dioxide
Photosynthesis involves the conversion of light energy into chemical energy by chlorophyll. In this process, carbon dioxide is reduced to carbohydrates.

Page No 28:

Question 96:

The opening and closing of the stomatal pores depends upon:
(a) oxygen
(b) water in guard cells
(c) temperature
(d) concentration of CO2 in stomata

Answer:

(b) water in guard cells
When guard cells have water, stomatal pores open and when water moves out of the guard cells, these pores close. 

Page No 28:

Question 97:

Most of the plants absorb nitrogen in one of the following forms. This is:
(a) proteins
(b) nitrates and nitrites
(c) urea
(d) atmospheric nitrogen

Answer:

(b) nitrates and nitrites
Plants cannot absorb atmospheric nitrogen. Plants can uptake nitrogen in the form of nitrates and nitrites only.

Page No 28:

Question 98:

The first enzyme to mix with food in the digestive tract is:
(a) pepsin
(b) cellulose
(c) amylase
(d) trypsin

Answer:

(c) amylase
The digestion of food begins in the mouth by the action of salivary amylase.

Page No 28:

Question 99:

Which of the following is the correct statement?
(a) heterotrophs synthesise their own food
(b) heterotrophs utilize solar energy for photosynthesis
(c) heterotrophs do not synthesise their own food
(d) heterotrophs are capable of converting carbon dioxide and water into carbohydrates

Answer:

(c) Heterotrophs do not synthesise their own food.
Heterotrophs cannot synthesis their food.

Page No 28:

Question 100:

In which of the following groups of organisms the food material is broken down outside the body and then absorbed?
(a) Mushroom, Green plants, Amoeba
(b) Yeast, Mushroom, Bread mould
(c) Paramecium, Amoeba, Cuscuta
(d) Cuscuta, Lice, Tapeworm

Answer:

(b) Yeast, Mushroom, Bread mould
Fungi (yeast, mushroom, bread mould) are saprophytes. They obtain their food by breaking it outside the body and then absorbing it.

Page No 28:

Question 101:

Which of the following is the correct sequence of parts as they occur in the human alimentary canal?
(a) Mouth → Stomach → Small intestine → Oesophagus → Large intestine
(b) Mouth → Oesophagus → Stomach → Large intestine → Small intestine
(c) Mouth → Stomach → Oesophagus → Small intestine → Large intestine
(d) Mouth → Oesophagus → Stomach → Small intestine → Large intestine

Answer:

d) Mouth → Oesophagus → Stomach → Small intestine → Large intestine

The correct sequence of the parts as they occur in the human alimentary canal is given below.
Mouth → Oesophagus → Stomach → Small intestine → Large intestine

Page No 28:

Question 102:

When a person eats sugary food, then organisms A present in his mouth act on sugar to produce a substance B. The substance B first dissolves the calcium salts from the top part C of the tooth and then from its middle part D forming holes E. These holes ultimately reach the part F in the lower part of tooth which contains nerves and blood vessels. The substance B irritates the nerve endings inside the tooth causing toothache.
(a) What are (i) organisms A, and (ii) substance B?
(b) What are (i) part C, and (ii) part D, of tooth known as?
(c) By what name are the holes E in the tooth known?
(d) Name the part F of the tooth.
(e) What will happen if organisms A reach part F of the tooth known?

Answer:

(a) (i) Organism A is bacteria and (ii) substance B is acid.

(b) (i) Part C is the tooth enamel and (ii) part D is the dentine of the tooth.

(c) The small holes, E, are known as cavities.

(d) F is the pulp of the tooth.

(e) When bacteria (organism A) reaches the pulp (part F) of the tooth, it irritates the nerve endings and causes toothache.



Page No 29:

Question 103:

If the teeth are not cleaned regularly, they become covered with a sticky yellowish layer W of food particles and bacteria. Since layer W covers the teeth, the alkaline liquid X secreted by glands Y inside the mouth cannot reach the teeth surface to neutralise the acid formed by the action of organisms Z on sugary food, and hence tooth decay sets in.
(a) What is W known as?
(b) What is (i) X, and (ii) Y?
(c) What are organisms Z?
(d) State one way of removing layer W from the teeth.

Answer:

(a) W is the dental plaque.

(b) (i) X refers to the saliva, while (ii) Y refers to the salivary glands.

(c) Organisms Z are bacteria.

(c) Layer of W, i.e. dental plaque, can be removed by regular brushing of teeth.

Page No 29:

Question 104:

When a person puts food in his mouth, then teeth cut it into small pieces, chew and grind it. The glands A in the mouth secrete a substance B which is mixed with the food by tongue. The substance B contains an enzyme C which starts the digestion of food in the mouth. The slightly digested food from the mouth goes down a tube D. The special type of movements E in the walls of tube D push the food into stomach for further digestion. The stomach wall secretes gastric juice containing three substance F, G and H. One of the functions of F is to kill bacteria which may enter the stomach with food. The substance G protects the inside layer of stomach from the damaging effect of substance F whereas substance H is an enzyme for digestion. The partially digested food then enters into small intestine for further digestion.
(a) What is (i) gland A (ii) substance B, and (iii) enzyme C?
(b) Name the tube D.
(c) What is the movement E known as?
(d) What are (i) F (ii) G, and (iii) H?

Answer:

(a) (i) Gland A is salivary gland.
(ii) Substance B is saliva.
(iii) Enzyme C is salivary amylase.

(b) Tube D is oesophagus.

(c) The movement E is known as peristaltic movement.

(d) (i) F is hydrochloric acid, (ii) G is mucus and (iii) H is pepsin.

Page No 29:

Question 105:

The partially digested food coming from the stomach of a person enters a long and narrow organ A in his body. The organ A receives the secretion of two glands : liver and pancreas. Liver secretes a greenish-yellow liquid B which is normally stored in the organ C. Pancreas secretes pancreatic juice which contains three digestive enzymes D, E and F. The intestinal juice completes the process of digestion of food. The inner wall of organ A has millions of tiny finger-like projections G which help in the rapid absorption of digested food into blood stream. The undigested part of food then passes into wider tube H which absorbs most of the water from undigested food. The last part of tube H called I stores this undigested food (or waste) for some time. The undigested food is then passed out though opening J as faeces in the process known as K.
(a) Name the organ A.
(b) Name (i) liquid B, and (ii) organ C.
(c) What are the digestive enzymes D, E and F?
(d) Name the projections G present on the inner wall of organ A.
(e) Name (i) tube H (ii) part I (iii) opening J, and (iv) process K.

Answer:

(a) The organ A is small intestine.

(b) (i) Liquid B is bile and (ii) organ C is gall bladder.

(c) The digestive enzymes D, E and F are amylase, trypsin and lipase, respectively.

(d) The projections G are villi that are present on the inner wall of organ A.

(e) (i) Tube H is the large intestine, (ii) part I is the rectum, (iii) opening J is the anus and (iv) the process K is egestion or defecation.

Page No 29:

Question 106:

A unicellular animal P having no fixed shape ingests a food particle by forming temporary finger-like projections Q. The food particle is engulfed with a little surrounding water to form a temporary stomach R inside it. The chemicals S from surrounding cytoplasm enter into R and break down food into small and soluble molecules by chemical reactions. The digested food is absorbed directly into cytoplasm by the process T. The undigested food is thrown out of the body by the rupture of a cell organelle U in a process called V.
(a) Name the unicellular animal P.
(b) What are (i) Q, and (ii) R?
(c) Name (i) chemical S, and (ii) process T.
(d) Name (i) organelle U, and (ii) process V.

Answer:

(a) The unicellular animal P is Amoeba.

(b) (i) Q is pseudopodia and (ii) R is the food vacuole.

(c) (i) Chemical S is the digestive enzyme and (ii) process T is diffusion.

(d) (i) Organelle U is cell membrane and (ii) process V is egestion.

Page No 29:

Question 107:

There are four organisms A, B, C and D. The organism A eats only the flesh of other animals as food. The organism B can eat grains, fruits and vegetables as well as meat and fish. The organism C can make the food itself from simple inorganic substances present in the environment by utilising sunlight energy. On the other hand, organism D eats only plants and their products as food.
(a) Which organism is (i) omnivore (ii) herbivore, and (ii) carnivore?
(b) Which organism is an autotroph?
(c) Which organism is/are heterotroph(s)?
(d) Which organism can be a producer?
(e) Which organism is/are consumer (s)?
(f) Give one example each of organisms which could be like (i) A (ii) B (iii) C, and (iv) D

Answer:

(a) (i) Organism B refers to an omnivore, (ii) organism D refers to a herbivore and (iii) organism A refers to a carnivore.

(b) Organism C is an autotroph.

(c) The organisms A, B and D are heterotrophs as they obtain food from other organisms and cannot synthesise their own food.

(d) Organism C can be a producer as it is an autotroph.

(e) The organisms A, B and D are consumers as they all are heterotrophs.

(f) The examples of organisms A, B, C and D are lion, crow, green plants (like mango) and cow, respectively.



Page No 30:

Question 108:

The organisms A, B and C can obtain their food in three different ways. Organism A derives its food from the body of another living organism which is called its D, without killing it. The organism B takes in the solid food by the process of ingestion, digests a part of this food and throws out undigested food in the process called E. The organism C obtains its food from dead and decaying plants.
(a) What is the mode of nutrition of (i) organism A (ii) organism B, and (iii) organism C?
(b) What is the organism like D called?
(c) Name the process E.
(d) Give one example each of organisms like (i) A (ii) B, and (iii) C.
(e) What is the general name of three modes of nutrition exhibited by organisms A, B and C?

Answer:

(a) (i) Organism A has parasitic mode of nutrition, (ii) organism B has holozoic mode of nutrition and (iii) organism C has saprophytic mode of nutrition.

(b) The organisms like D are called hosts.

(c) The process E is egestion.

(d) The example of organisms like (i) A is Cuscuta, (ii) B is cow and (iii) C is mushroom.

(e) The general name of the three modes of nutrition exhibited by organism A, B and C are parasitic nutrition, holozoic nutrition and saprophytic nutrition, respectively.

Page No 30:

Question 109:

An organism A which cannot move from one place to another, makes a simple food B from the substances C and D available in the environment. This food is made in the presence of a green coloured substance E present in organs F in the presence of light energy in a process called G. Some of the simple food B also gets converted into a complex food H for storage purposes. The food H gives a blue-black colour with dilute iodine solution.
(a) What is (i) organism A (ii) food B, and (iii) food H?
(b) What are C and D?
(c) Name (i) green coloured substance E, and (ii) organ F.
(d) What is the process G?

Answer:

(a) (i) Organism A is a green plant, (ii) food B is glucose and (iii) food H is starch.

(b) C is carbon dioxide and D is water.

(c) (i) The green coloured substance E is chlorophyll and (ii) organ F is a leaf.

(d) The process G is photosynthesis.

Page No 30:

Question 110:

X is a wild animal which eats only the flesh of other animals whereas Y is a domestic animal which feeds mainly on green grass.
(a) What are animals like X known as?
(b) What are animals Y known as?
(c) Which animal, X or Y, has a longer small intestine? Why?
(d) Name one animal which is like X.
(e) Name one animal which is like Y.

Answer:

(a) Animals like X are known as carnivores.

(b) Animals like Y are known as herbivores.

(c) Animals like X have longer small intestine as they are grass eating animals and they need long intestine to digest the cellulose present in the grass.

(d) Lion is a carnivore.

(e) Cow is a herbivore.



Page No 46:

Question 1:

Do all cells use oxygen to produce energy?

Answer:

No, all cells do not use oxygen to produce energy. Cells can also produce energy by anaerobic respiration, where oxygen is not required.

Page No 46:

Question 2:

Name one substance which is produced in anaerobic respiration by an organism but not in aerobic respiration.

Answer:

Ethanol is produced as the result of the breakdown of pyruvate during anaerobic respiration, not in aerobic respiration.

Page No 46:

Question 3:

Name one organism which can live without oxygen.

Answer:

Yeast can live without oxygen as it can respire anaerobically.

Page No 46:

Question 4:

In which type of respiration, aerobic or anaerobic, more energy is released?

Answer:

In aerobic respiration, more energy is released because there is complete breakdown of food.

Page No 46:

Question 5:

Name the substance whose build up in the muscles during vigorous physical exercise may cause cramps.

Answer:

Lactic acid, which is formed in muscles during vigorous physical exercise, may cause cramps.

Page No 46:

Question 6:

Which part of roots is involved in the exchange of respiratory gases?

Answer:

Root hair is involved in the exchange of respiratory gases as they are in direct contact with the air present in the soil.



Page No 47:

Question 27:

Explain why, a land plant may die if its roots remain waterlogged for a long time.

Answer:

The roots of plant can not respire if they remain water logged for a long time. This is because water replaces the air present between the soil particles. Thus, the roots do not get enough air to respire and the plant may die.

Page No 47:

Question 28:

What are the differences between aerobic and anaerobic respiration? Name some organisms that use anaerobic mode of respiration.

Answer:

Aerobic respiration Anaerobic respiration
It occurs in the presence of oxygen. It occurs in the absence of oxygen.
Here, complete breakdown of food occurs. Here, partial breakdown of food occurs.
Here, the end products are carbon dioxide and water. Here, the end products are ethanol and carbon dioxide (as in yeast) or lactic acid (as in animal muscles).
It releases a large amount of energy.  It produces less amount of energy.

The organisms that use anaerobic mode of respiration include some bacteria and microorganisms such as yeast.

Page No 47:

Question 29:

Name the final product/products obtained in the anaerobic? respiration, if it takes place:
(a) in a plant (like yeast).
(b) in an animal tissue (like muscles).

Answer:

(a) During anaerobic respiration in plants (like yeast), ethanol, carbon dioxide and energy are the final products.
(b) During anaerobic respiration in an animal tissue (like muscles), lactic acid and energy are the final products.

Page No 47:

Question 30:

What type of respiration takes place in human muscles during vigorous physical exercise? Give reason for your answer.

Answer:

Anaerobic respiration takes place in human muscles during vigorous physical exercise. This is because oxygen gets used up at a faster rate in the muscle cells than can be supplied by the blood-carrying oxygen. 

Page No 47:

Question 31:

Name the type of respiration in which the end products are:
(a) C2H5OH and CO2
(b) CO2 and H2O
(c) Lactic acid
Give one example of each case where such a respiration can occur.

Answer:

(a) In the anaerobic respiration that takes place in yeast, the end products are C2H5OH and CO2.
(b) In the aerobic respiration that takes place in human cells in the presence of oxygen, the end products are CO2 and H2O.
(c) In the anaerobic respiration that takes place in animal tissues like muscle cells, the end product is lactic acid.

Page No 47:

Question 32:

Define breathing. State the differences between breathing and respiration.

Answer:

Breathing is a physical mechanism in which an organism takes up oxygen from the air and gives out carbon dioxide.
 

Breathing Respiration
It is a physical process. It is a biochemical process.
It involves exchange of gases. It involves exchange of gases along with the oxidation of food.
It involves the lungs, where the exchange of gases takes place. Along with the lungs, it involves the mitochondria of the cells, where oxidation of food takes place.

Page No 47:

Question 33:

What are the different ways in which glucose is oxidised to provide energy in various organisms?

Answer:

Glucose is oxidised in two ways to provide energy.
(a) Aerobic respiration: Glucose is completely oxidised to carbon dioxide and water in the presence of oxygen, with the release of a considerable amount of energy. This type of oxidation occurs in most of the living organisms such as human beings, birds, snakes, frogs, fish, etc.
(b) Anaerobic respiration: This type of respiration occurs in the absence of oxygen. In this type of oxidation, glucose is partially oxidised to ethanol and carbon dioxide (yeast and other bacteria) or lactic acid (muscles during physical exercise and some bacteria) with the release of a small amount of energy.

Page No 47:

Question 7:

Name the process by which plant parts like roots, stems, and leaves get oxygen required for respiration.

Answer:

All the plant parts like roots, stems and leaves get oxygen by passive diffusion, which is required for respiration.

Page No 47:

Question 8:

Name the pores in a leaf through which respiratory exchange of gases takes place.

Answer:

Stomata are the pores present on the surface of the leaves through which exchange of gases takes place.

Page No 47:

Question 9:

Name the areas in a woody stem through which respiratory exchange of gases takes place.

Answer:

The outer covering of the woody stems, which is known as the bark, has lenticels through which respiratory exchange of gases takes place.

Page No 47:

Question 10:

What is the name of the extensions of the epidermal cells of a root which help in respiration?

Answer:

Root hair is the extension of the epidermal cells of a root, which help in respiration.

Page No 47:

Question 11:

Out of photosynthesis and respiration in plants, which process occurs:
(a) all the time?
(b) only at daytime?

Answer:

(a) Respiration occurs all the time.
(b) Photosynthesis occurs only at daytime as it can take place only in the presence of sunlight.

Page No 47:

Question 12:

Name the organs of breathing in fish.

Answer:

In fish, gills are the organs of breathing.

Page No 47:

Question 13:

Name an animal which absorbs oxygen through its moist skin.

Answer:

Earthworms absorb oxygen through their moist skin.

Page No 47:

Question 14:

Name an animal which depends on simple diffusion of gases for breathing.

Answer:

Amoeba depends on simple diffusion of gases for breathing.

Page No 47:

Question 15:

Name two animals which breathe through gills.

Answer:

Aquatic animals like fishes, prawns and mussels breath through gills.

Page No 47:

Question 16:

The trachea divides into tow tubes at its lower end. What is the name of these tubes?

Answer:

The trachea divides into two tubes at its lower end, which are known as bronchi.

Page No 47:

Question 17:

Where does the blood absorb oxygen in the human body?

Answer:

Blood absorbs oxygen in the lungs. The exchange of gases takes place in the alveoli of lungs and the blood present in the blood capillaries surrounding the alveoli.

Page No 47:

Question 18:

Name the red pigment which carries oxygen in blood.

Answer:

Haemoglobin is the red pigment that is present in red blood cells. It carries oxygen in the blood.

Page No 47:

Question 19:

Which gases are exchanged in your lungs?

Answer:

Carbon dioxide and oxygen are exchanged in the lungs. Oxygen from the inhaled air is exchanged for carbon dioxide present in the blood.

Page No 47:

Question 20:

Where in the lungs does gas exchange take place?

Answer:

Gas exchange takes place in the alveoli of the lungs.

Page No 47:

Question 21:

What is the name of tiny air-sacs at the end of smallest bronchioles in the lungs?

Answer:

Alveoli are the tiny air-sacs at the end of smallest bronchioles in the lungs.

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Question 22:

What is the other name of wind-pipe?

Answer:

Wind-pipe is also known as trachea.

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Question 23:

What organs are attached to the two bronchi?

Answer:

The two lungs are attached to the two bronchi.

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Question 24:

In the lungs:
(a) what substance is taken into the body?
(b) what substance is removed from the body?

Answer:

(a) Oxygen is taken into the body
(b) Carbon dioxide is removed from the body.

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Question 25:

State whether the following statements are true or false:
(a) During respiration, the plants take CO2 and release O2.
(b) Energy can be produced in cells without oxygen.
(c) Fish and earthworm exchange gases during respiration in the same way.

Answer:

(a) False
During respiration, the plants take oxygen and release carbon dioxide.
(b) True
Energy can be produced in the cells even without oxygen.
(c) False
Fish breathe through gills and earthworms breathe through their moist skin.

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Question 26:

Fill in the following blanks with suitable words:
(a) The organs of respiration in man are the...........
(b) The actual exchange of gases takes place in the..........of the lungs.
(c) ..........in the lungs provide a very large surface area for gaseous exchange.
(d) Yeast undergoes..............respiration whereas Amoeba undergoes..............respiration.
(e) Gills are the breathing organs in............

Answer:

(a) The organs of respiration in man are the lungs.
(b) The actual exchange of gases takes place in the alveoli of the lungs.
(c) Alveoli in the lungs provide a very large surface area for gaseous exchange.
(d) Yeast undergoes anaerobic respiration, whereas Amoeba undergoes aerobic respiration.
(e) Gills are the breathing organs in aquatic animals (fish).



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Question 34:

Explain why, when air is taken in and let out during breathing, the lungs always contain a residual volume of air.

Answer:

When air is taken in and let out during breathing, the lungs always contain a residual amount of air. This is because there is sufficient time for the oxygen to be absorbed into the blood and for the carbon dioxide to be released from the blood.

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Question 35:

Explain why, it is dangerous to inhale air containing carbon monoxide.

Answer:

Carbon monoxide combines with haemoglobin and forms carboxyhaemoglobin by replacing the oxygen. This reduces the oxygen carrying capacity of the blood. Due to the lack of oxygen, the person cannot breathe properly. In extreme cases, a person may even die due to oxygen starvation. Hence, it is dangerous to inhale the air containing carbon monoxide. 

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Question 36:

Describe the process of respiration in Amoeba. State whether it is anaerobic respiration or aerobic respiration.

Answer:

Ameoba is a unicellular organism. It depends on simple diffusion of gases for breathing. The exchange of gases in Amoeba takes place through its cell membrane. Since it lives in water, the oxygen from water diffuses into the body of Amoeba through its cell membrane. This oxygen is used for respiration inside the Amoeba cell. The process of respiration continuously produces carbon dioxide that diffuses out through the membrane of Amoeba into the surrounding water.
 Respiration in Amoeba is aerobic.

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Question 37:

State the three common features of all the respiratory organs like skin, gills and lungs.

Answer:

All the respiratory organs like skin, gills and lungs have three common features.
(a) They have a large surface area to get enough oxygen.
(b) They have thin walls for easy diffusion and exchange of respiratory gases.
(c) They have a rich blood supply for transporting respiratory gases.

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Question 38:

Describe the process of respiration in fish.

Answer:

Fish have special organs for breathing. They are called gills. For breathing, the fish use the oxygen dissolved in water. They breathe by taking in water through their mouth and sending it over the gills. When water passes over the gills, the dissolved oxygen is extracted. The water then goes out through the gill slits. The extracted oxygen is absorbed by the blood and carried to all the parts of the body. The carbon dioxide produced during respiration is brought back by the blood into the gills for expelling into the surrounding water. The gaseous exchange in fish takes place in the gills. 

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Question 39:

What would be the consequences of deficiency of haemoglobin in our bodies?

Answer:

The deficiency of haemoglobin in our bodies would reduce the oxygen carrying capacity of the blood, resulting in breathing problems, tiredness and lack of energy. Due to this, we would look pale and lose weight.

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Question 40:

Describe the process of respiration in the following parts of a plant:
(a) Root
(b) Stem
(c) Leaves

Answer:

(a) The respiration in roots takes place by the diffusion of respiratory gases through the root hair. The root hair take the oxygen required for respiration from the air present in-between the soil particles, by the process of diffusion. The oxygen reaches all the other cells of the root for respiration. During respiration, the carbon dioxide gas produced in the cells of the root  moves out through the same root hair by the process of diffusion.

(b) The stems of herbaceous plants have stomata. The oxygen from air diffuses into the stem of a herbaceous plant through stomata and reaches all the cells, for respiration. The carbon dioxide gas produced during respiration diffuses out into the air, through the same stomata. In woody stems, the bark has lenticels for gaseous exchange.

(c) â€‹The leaves of a plant have tiny pores called stomata. The oxygen from air diffuses into a leaf through stomata and reaches all the cells, where it is used in respiration. The carbon dioxide gas that is produced during respiration, diffuses out from the leaf into the air through the same stomata. 

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Question 41:

(a) What is meant by aquatic animals and terrestrial animals?
(b) From where do the aquatic animals and terrestrial animals obtain oxygen for breathing and respiration?

Answer:

(a) Terrestrial animals live on land. They respire through lungs. Examples of terrestrial animals are human beings, cows, cats, dogs, etc.
Aquatic animals live in water. They have a special organ for respiration. They are called gills. An example of aquatic animals is fish.
(b) Aquatic animals obtain the oxygen dissolved in water for breathing and respiration. Terrestrial animals obtain oxygen present in air for breathing and respiration. 

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Question 42:

Why do fishes die when taken out of water?

Answer:

Fish do not have lungs that can utilise the oxygen of the air for breathing and respiration. The fish have gills. Gills can only extract the dissolved oxygen from water and provide it to the fish. Gills cannot take in the oxygen from the air. Since fish do not get oxygen for breathing when taken out of water, they die. 

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Question 43:

Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?

Answer:

The aquatic organisms use the oxygen dissolved in water to carry out respiration. Since the amount of dissolved oxygen in water is low as compared to the amount of oxygen in air, the rate of breathing in aquatic animals is much faster than in terrestrial animals.

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Question 44:

Name the energy currency in the living organisms. When and where is it produced?

Answer:

The energy currency in the living organisms is adenosine triphosphate (ATP). It is produced in the mitochondria, during respiration.

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Question 45:

Explain why, plants have low energy needs as compared to animals.

Answer:

Plants do not need to move from one place to another. Movements in a plant is usually at the cellular level. Thus, a far less amount of energy is required by the plants. Animals, on the other hand, need to move from one place to another in search of food. So, the energy need of animals is much higher than plants.

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Question 46:

Explain how, it would benefit deep sea divers if humans also had gills.

Answer:

If humans also had gills, the deep sea divers would not have to carry oxygen cylinders with them for breathing under the water. 

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Question 47:

(a) What is the function of the respiratory system?
(b) What are the major organs of respiratory system in man (or humans)?
(c)  Draw a labelled diagram of the human respiratory system.

Answer:

(a) The main function of the respiratory system is to breathe in oxygen for respiration and to breathe out carbon dioxide, and to provide energy to the body by the breaking down the food particles.

(b) The major organs of respiratory system in a human being are nose, nasal passage, trachea, bronchi, lungs and diaphragm.

(c) Human Respiratory System:

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Question 48:

(a) Explain how, the air we breathe in gets cleaned while passing through the nasal passage.
(b) Why do the walls of trachea not collapse when there is less air in it?
(c) How are oxygen and carbon dioxide exchanged in our body during respiration?
(d) How are lungs designed in human beings to maximise the exchange of gases?

Answer:

(a) The nasal passage is lined with fine hair and mucus. When air passes through the nasal passage, the dust particles and other impurities present in it are trapped by the nasal hair and mucus. Due to this, only clean air reaches the lungs.

(b) The walls of trachea do not collapse when there is less air in it because trachea is supported by rings of soft bones called cartilage.

(c) Gaseous exchange in our body takes place in the alveoli of lungs. The oxygen of air diffuses out from the alveoli walls into the blood. As the blood passes through the tissues of the body, the oxygen present in it diffuses into the cells. This oxygen combines with the digested food present in the cells, to release energy. Carbon dioxide gas, which is produced as a waste product during respiration in the cells of the body tissues, diffuses into the blood. Blood carries the carbon dioxide back to the lungs, where it diffuses into the alveoli.

(d) The human lungs have been designed to maximise the exchange of gases.
There are millions of alveoli in the lungs. The presence of millions of alveoli in the lungs provide a very large area for the exchange of gases. The availability of large surface area maximises the exchange of gases.

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Question 49:

(a) Give the main points of difference between respiration in plants and respiration in animals.
(b) Describe the exchange of gases which takes place in the leaves of a plant (a) during daytime, and (b) at night.
(c) Which contains more carbon dixoide : exhaled air or inhaled air? Why?

Answer:

(a) 

Respiration in plants Respiration in animals
All the parts of a plant perform respiration individually. An animal performs respiration as a single unit.
There is little transport of respiratory gases from one part of the plant to the other. Respiratory gases are usually transported over long distances inside an animal.
The respiration in plants occurs at a slow rate. The respiration in animals occurs at a much faster rate.

(b) (a) During daytime, the leaves use some of the oxygen produced through photosynthesis for respiration. For photosynthesis, the leaves not only use the carbon dioxide produced through respiration, but some carbon dioxide is also taken in from the air.
Thus, during daytime, oxygen diffuses out and carbon dioxide diffuses in.

 (b) At night, as photosynthesis does not takes place, oxygen is not produced. Thus, oxygen from air diffuses into the leaves to carry out respiration. And carbon dioxide produced by respiration diffuses out into the air. So, at night, oxygen diffuses in and carbon dioxide diffuses out.

(c) Exhaled air contains more carbon dioxide because we exhale to remove the waste product, i.e. carbon dioxide, from our body.

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Question 50:

(a) "Respiration is a vital function of the body". Justify this statements.
(b) What is the main difference between aerobic respiration and anaerobic respiration? Give one example of each.
(c) What type of repiration takes place (i) in yeast, and (ii) in humans?

Answer:

(a) Respiration is a vital function of the body because it provides energy for carrying out all the life processes that are necessary to keep the organisms alive. Most living things need oxygen to obtain energy from food. This oxygen reacts with the food molecules present in the body cells and burns them slowly to release energy. This energy is stored as ATP molecules in the cells. The process of releasing energy from food is called respiration.

(b)

Aerobic Respiration Anaerobic Respiration
It takes place in the presence of oxygen. It takes place in the absence of oxygen.
Complete breakdown of food occurs in aerobic respiration. Partial breakdown of food occurs in anaerobic respiration.
The end products are carbon dioxide and water. The end products may be ethanol and carbon dioxide (as in yeast cells) or lactic acid (as in muscle cells).
It produces a considerable amount of energy. Much less energy is produced in anaerobic respiration.

(c) (i) Anaerobic respiration takes place in yeast.
(ii) Aerobic respiration takes place in humans.

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Question 51:

(a) Why is diffusion insufficient to meet the oxygen requirements of large multicellular organisms like humans?
(b) What type of arrangement exists in the bodies of large animals to meet their oxygen requirements adequately?
(c) What advantage a terrestrial animal has over an aquatic animal with regard to obtaining oxygen for respiration?

Answer:

(a) In small unicellular animals, such as Amoeba, the volume of their body is so small that oxygen can be introduced quickly into the whole body by the process of diffusion. This is because the cell of Amoeba is so small that the oxygen does not have to go far. But in case of large multicellular animals like humans, the volume of the body is so big that oxygen cannot quickly diffuse into all the cells of the body. This is because in these cases, the oxygen has to travel a very large distance to reach each and every cell of the body.

(b) In large animals, there is a blood circulatory system to quickly carry the oxygen to all the parts of the body.

(c) A terrestrial animal is surrounded by an oxygen-rich atmosphere from where it can take any amount of oxygen. An aquatic animal uses the oxygen dissolved in water to carry out respiration. The amount of oxygen dissolved in water is low as compared to the amount of oxygen in the air.

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Question 52:

Which of the following is not produced during anaerobic respiration in unicellular fungus?
(a) C2H5OH
(b) H2O
(c) CO2
(d) ATP

Answer:

(b) H2O
Anaerobic respiration occurs in absence of oxygen. One molecule of glucose breaks down to release two molecules of ethanol, two molecules of carbon dioxide and two ATP molecules.

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Question 53:

One of the following organisms can live without oxygen of air. This organism is:
(a) Amoeba
(b) Yak
(c) Yeast
(d) Leech

Answer:

(c) Yeast
Yeast can live without the oxygen present in the air. This is because it obtains energy by the process of anaerobic respiration.

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Question 54:

During respiration, the exchange of gases takes place in:
(a) bronchi
(b) alveoli
(c) bronchioles
(d) trachea

Answer:

(b) alveoli
Alveoli are the pouch-like air sacs at the end of the small bronchioles. The walls of alveoli are very thin. Also, they are surrounded by very thin blood capillaries. It is in the alveoli that the gaseous exchange takes place.

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Question 55:

In one of the following organisms, the gaseous exchange during repiration does not take place through cell membrane/skin. This organism is:
(a) Electric eel
(b) Leech
(c) Earthworm
(d) trachea

Answer:

(a) Electric eel
Electric eel respires through gills. Leech and earthworm respire through their skin.



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Question 56:

Which of the following is correct for the process of anaerobic respiration?

  Carbon dioxide always produced A lot of energy released
(a) No Yes
(b) No No
(c) Yes No
(d) Yes Yes

Answer:

(b) No No
There are two pathways through which anaerobic respiration occurs.  In micro-organisms such as yeast and bacteria, the glucose is broken down into ethanol and carbon dioxide, and releases very little energy. In the other pathway, glucose is broken down into only lactic acid with the release of little energy. This occurs in the muscles during strenuous exercise. Therefore, carbon dioxide is not always produced during anaerobic respiration.

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Question 57:

Which of the following increases in muscle cells when they are lacking in oxygen?
(a) carbon dioxide
(b) lactose
(c) lactic acid
(d) uric acid

Answer:

(c) lactic acid
In the muscle cells that lack oxygen, concentration of lactic acid is increased. This is because, here, anaerobic respiration takes place in which glucose is converted into lactic acid with the release of a small amount of energy.

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Question 58:

Internal respiration may be defined as:
(a) breathing in and releasing of oxygen in the tissue
(b) the oxidation of food substances to release energy
(c) the building up (synthesis) of complex substances
(d) getting rid of carbon dixode that would accumulate in the tissues.

Answer:

(b) the oxidation of food substances to release energy
Internal respiration may be defined as the oxidation of food substances to release energy.

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Question 59:

When air is blown from mouth into a test-tube containing lime water, the lime water turns milky due to the presence of:
(a) oxygen
(b) carbon dioxide
(c) nitrogen
(d) water vapour

Answer:

(b) carbon dioxide
Lime water turns milky due to the presence of carbon dioxide in the exhaled air.

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Question 60:

Which of the following is the correct sequence of air passage during inhalation?
(a) nostrils → larynx → pharynx → trachea → lungs
(b) nasal passage → trachea → pharynx → larynx → alveoli
(c) larynx → nostrils → pharynx → lungs
(d) nostrils → pharynx → larynx → trachea → alevoli

Answer:

(d) nostrils → pharynx → larynx → trachea → alveoli

The correct sequence of air passage during inhalation is as follows:
Nostrils → Nasal chambers → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli

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Question 61:

Lack of oxygen in muscles often leads to cramps in the legs of sprinters. This is due to conversion of pyruvate to:
(a) ethanol
(b) carbon dioxide
(c) acetic acid
(d) lactic acid

Answer:

(d) lactic acid
Lack of oxygen in muscles causes accumulation of lactic acid, due to anaerobic respiration. Accumulation of lactic acid leads to cramps in the legs of sprinters.    

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Question 62:

During the deficiency of oxygen in tissues of human beings, pyruvic acid is converted into lactic acid in:
(a) ethanol
(b) chloroplast
(c) mitochondria
(d) golgi body

Answer:

(c) mitochondria
During anaerobic respiration in human beings, pyruvic acid is converted into lactic acid in the mitochondria of the muscle cells.

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Question 63:

Which of the following statements are correct?
(i) pyruvate can be converted into ethanol and carbon dioxide by yeast
(ii) fermentation takes place in the case of aerobic bacteria
(iii) fermentation takes place in mitochondria
(iv) fermentation is a form of anaerobic respiration
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (i) and (iv)
(d) (ii) and (iii)

Answer:

(c) (i) and (iv)
Statements (i) and (iv) are correct. The explanation for wrong statements are as follows:
(ii) Fermentation takes place in the case of anaerobic bacteria.
(iii) Fermentation takes place in cytoplasm.

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Question 64:

Which of the following statements are true about respiration?
(i) during inhalation, ribs move inward and diaphragm is raised.
(ii) the gaseous exchange takes place in the alveoli.
(iii) haemoglobin has greater affinity for carbon dioxide than oxygen.
(iv) alveoli increase surface area of the exchange of gases
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)

Answer:

(d) (ii) and (iv)
Statements (ii) and (iv) are correct. The explanation for incorrect statements is given below:
(i) During inhalation, ribs move outward and diaphragm moves downward.
(iii) Haemoglobin has greater affinity for carbon monoxide than oxygen.

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Question 65:

Which of the following is known as the energy currency of the cells in biology?
(a) DTP
(b) PDP
(c) ATP
(d) DDT

Answer:

(c) ATP
In biology, ATP is known as the energy currency of a cell. It is a high energy molecule that stores the energy.

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Question 66:

The two organisms which breathe only through their moist skin are:
(a) fish and frog
(b) frog and earthworm
(c) leech and earthworm
(d) fish and earthworm

Answer:

(c) leech and earthworm
Leech and earthworm breathe only through their moist skin. Fish breathe through gills, while frogs breathe through lungs and skin.

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Question 67:

One of the following animals does not use tracheae as the respiratory organs. This animal is:
(a) grasshopper
(b) prawn
(c) mosquito
(d) cockroach

Answer:

(b) prawn
Prawn is an aquatic animal that respires through gills. Insects such as grasshopper, mosquito and cockroach respire through tracheae.

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Question 68:

The photosynthesis in a plant is not taking place during the day time if the plant is releasing:
(a) water vapour
(b) oxygen
(c) carbon dioxide
(d) all the above

Answer:

(c) carbon dioxide
During daytime, the carbon dioxide produced through respiration is used up in photosynthesis by leaves. In fact, more carbon dioxide is taken in from the air for this purpose.
So, oxygen is diffused out and carbon dioxide is diffused in.

Hence, if a plant is releasing carbon dioxide during the daytime, then photosynthesis is not taking place.

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Question 69:

The breathing and respiration in woody stem of a plant takes place through:
(a) root hair
(b) lenticels
(c) closed stomata
(d) open stomata

Answer:

(b) lenticels
In woody stems, the bark (outer covering of the stem) has lenticels for gaseous exchange.



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Question 70:

One of the following organism does not depend on simple diffusion of gases for breathing and respiration. This organism is:
(a) Amoeba
(b) Prawn
(c) Planaria
(d) Bryophyllum

Answer:

(b) Prawn
Prawn is an aquatic animal that respires through gills. The gills extract oxygen dissolved in water and take away carbon dioxide from the body.

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Question 71:

During marathon, we sometimes get painful contractions of leg muscles due to the accumulation of one of the following in leg muscles. This is:
(a) carbon dioxide
(b) alcohol
(c) lactose
(d) lactic acid

Answer:

(d) lactic acid
During a marathon, most of the energy in our muscles is produced through aerobic respiration, while anaerobic respiration provides some extra energy needed under these conditions. The anaerobic respiration by the muscles brings about partial breakdown of glucose to form lactic acid. The accumulation of lactic acid in the muscles causes muscle cramps.

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Question 72:

In cockroaches, air enters the body through:
(a) lungs
(b) gills
(c) spiracles
(d) skin

Answer:

(c) spiracles
In insects (such as cockroaches, grasshoppers), the tiny holes called spiracles are present on the body. Air enters the body through these holes.

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Question 73:

Which of the following is most likely to have a much higher breathing rate?
(a) man
(b) fish
(c) dog
(d) sparrow

Answer:

(b) fish
Rate of breathing in aquatic animals is much faster than terrestrial animals. This is because a faster rate of breathing provides more oxygen to the aquatic animals.

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Question 74:

During the respiration of an organism A, 1 molecule of glucose produces 2 ATP molecules whereas in the respiration of another organism B, 1 molecule of glucose produces 38 ATP molecules.
(a) Which organism is undergoing aerobic respiration?
(b) Which organism is undergoing anaerobic respiration?
(c) Which type of organism, A or B, can convert glucose into alcohol?
(d) Name one organism which behaves like A.
(e) Name two organisms which behave like B.

Answer:

(a) Organism B is undergoing aerobic respiration.

(b) Organism A is undergoing anaerobic respiration. 

(c) In anaerobic respiration, glucose breaks down to form alcohol and carbon dioxide with the release of small amount of energy. Hence, organism A can convert glucose into alcohol.

(d) Yeast behaves like organism A.

(e) Humans and dogs behave like organism B.

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Question 75:

A, B and C are three living organisms. The organism A is a unicellullar fungus which can live without air. It is used in the commercial production of an organic compound P from molasses. The organism B is a unicellular animal which lives in water and feeds and moves by using pseudopodia. It breathes through an organelle Q. The organism C is a tiny animal which acts as a carrier of malarial parasite. It breathes and respires through a kind of tiny holes R and air-tubes S in its body.
(a) What are organisms (i) A (ii) B, and (iii) C?
(b) Name (i) P (ii) Q (iii) R, and (iv) S.
(c) Which organism/organisms undergo aerobic respiration?
(d) Which organism/organisms undergo anaerobic respiration?

Answer:

(a) (i) Organism A is yeast.
(ii) Organism B is Amoeba.
(iii) Organism C is mosquito.

(b) (i) P is alcohol.
(ii) Q is the cell membrane because Amoeba breathes through the cell membrane.
(iii) R is spiracle.
(iv) S is tracheae.

(c) Organisms B and C undergo aerobic respiration.

(v) Organism A, i.e. yeast, undergoes anaerobic respiration.

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Question 76:

There are five animals P, Q, R, S and T. The animal P always lives in water and has gills for breathing. The animal Q can stay in water as well as on land and can breathe both, through moist skin and lungs. The animal R lives in soil and breathes only through its skin. The animal S lives on land and breathes through spiracles and tracheae. And animal T lives in water and breathes through its cell membrane.
(a) Which of the animals could be Amoeba?
(b) Which of the animals could be frog?
(c) Which animal could be fish?
(d) Which animal could be grasshopper?
(e) Which animal could be earthworm?

Answer:

(a) T is Amoeba.

(b) Q is frog.

(c) P is fish.

(d) S is grasshopper.

(e) R is earthworm.

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Question 77:

Some sugar solution is taken in a test-tube and a little of substance X in powder form is added to it. The mouth of test-tube is closed with a cork and allowed to stand for sometime. On opening the cork, a characteristic smell of substance Y is obtained and a gas Z is also observed to be formed. The gas Z extinguishes a burning matchstick.
(a) What could be (i) X, (ii) Y, and (iii) Z?
(b) What is the process of converting sugar into substance Y by the action of X known as?
(c) What type of respiration is exhibited by X in the above process?

Answer:

(a) (i) X is yeast.
(ii) Y is ethanol.
(iii) Z is carbon dioxide.

(b) Fermentation is the process of converting sugar into substance Y by the action of X.

(c) Anaerobic respiration is exhibited by X in the above process.

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Question 78:

Consider the following chemical reactions which take place in different organisms/tissues under various conditions:
(i) Glucose    Respiration     Ethanol + Carbon dioxide + Energy
(ii) Glucose    Respiration     Carbon dioxide + Water + Energy
(iii) Glucose    Respiration     Lactic acid + Energy
(a) Name one organism which respires according to equation (i) above.
(b) Name one organism which respires according to equation (ii) above.
(c) When and where does respiration represented by equation (iii) above take place?
(d) Which equation/equations represent aerobic respiration?
(e) Which equation/equations represent anaerobic respiration?
(f) Which of the above reactions produces the maximum amount of energy?

Answer:

(a) Yeast shows anaerobic respiration.

(b) Humans show aerobic respiration.

(c) In humans beings, during high muscular activity, the respiration represented by equation (iii) occurs. It occurs in the muscle tissue.

(d) Equation (ii) represents aerobic respiration.

(e) Equation (i) represents anaerobic respiration.

(f) Aerobic respiration, i.e. the reaction represented by equation (ii), produces maximum amount of energy.



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Question 79:

When a person breathes in air, the air enters into his body through an organ A having two holes B in it. The air then passes through pharynx and larynx and enters into a tube C. The tube C divides into two smaller tubes D at its lower end. The two smaller tubes are attached to two respiratory organs E. Each smaller tube divides inside the organs E to form a large number of still smaller tubes called F. The smallest tubes F have air-sacs G at their ends in which gaseous exchange takes place in the body of the person. What are A, B, C, D, E, F and G?

Answer:

Here, A, B, C, D, E, F and G refer to the nose, nostrils, trachea, bronchi, lungs, bronchioles and alveoli, respectively.

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Question 80:

An organism X having breathing organs A lives on land. When organism X goes under water, it cannot survive for a long time unless carrying an oxygen cylinder. On the other hand, the organism Y having breathing organs B always lives in water and if taken out of water, it dies after a short while. A third organism Z having breathing organs C and D which lives on the banks of ponds, lakes and rivers can survive on land as well as in water equally well.
(a) What could organism X be? Name the breathing organs A.
(b) What could organism Y be? Name the breathing organs B.
(c) What could organism Z be? Name the breathing organs C and D.
(d) Out of X, Y and Z, which organism is (i) amphibian, (ii) aquatic, and (iii) terrestrial?

Answer:

(a) Organism X could be a human being. The breathing organs A are lungs.

(b) Organism Y could be a fish. The breathing organs B are gills.

(c) Organism Z could be a frog. The breathing organ C is skin and D are lungs.

(d) (i) Z is an amphibian.
(ii) Y is an aquatic organism.
(iii) X is a terrestrial organism.



Page No 72:

Question 1:

What is the name of tissues which transport:
(a) food in a plant?
(b) water and minerals in a plant?

Answer:

(a) In a plant, phloem transports the food.
(b) In a plant, xylem transports water and minerals.

Page No 72:

Question 2:

What substance/substances are transported in plants by:
(a) xylem vessels and tracheids?
(b) sieve tubes (or phloem)?

Answer:

(a) Xylem vessels and tracheids transport water in plants.
(b) Sieve tubes transport food in the plants.

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Question 3:

Which organ acts as a pump in the circulatory system?

Answer:

In the circulatory system, heart acts as a pump to push out blood.

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Question 4:

Veins and arteries carry blood. Which of these carry blood:
(a) away from the heart?
(b) back to the heart?

Answer:

(a) Arteries carry blood away from the heart.
(b) Veins carry blood back to the heart.

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Question 5:

Where does blood absorb oxygen?

Answer:

The blood absorbs oxygen in the lungs.

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Question 6:

What stops blood from flowing backwards through the heart?

Answer:

The valves present in the right and the left atrium prevent the blood from flowing backwards into the atria. 

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Question 7:

Name (i) largest artery, and (ii) largest vein, in our body.

Answer:

(a) The largest artery in our body is aorta.
(b) The largest vein in our body is vena cava.

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Question 8:

What gaseous waste products are excreted by plants?

Answer:

Carbon dioxide, water vapour and oxygen are the main gaseous waste products excreted by plants.

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Question 9:

Where is the dirty blood in our body filtered?

Answer:

In our body, the dirty blood is filtered in the kidneys.

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Question 10:

Name the procedure used in the working of artificial kidney.

Answer:

Dialysis is the procedure used in the working of artificial kidney.

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Question 11:

From the following terms, choose one term which includes the other four:
Plasma, Platelets, Blood, RBC, WBC

Answer:

Blood includes the other four terms. This is because plasma, platelets, RBC and WBC are the components of blood.

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Question 12:

What are the components of the transport system in highly organised plants?

Answer:

Xylem and phloem are the two main components of the transport system in the highly organised plants.

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Question 13:

Out of xylem and phloem, which one carries materials:
(a) upwards as well as downwards?
(b) only upwards?

Answer:

(a) Phloem carries materials both upwards as well as downwards.
(b) Xylem carries materials only upwards.



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Question 30:

What is xylem tissue? Name the two kinds of cells in xylem tissue. State whether these cells are living or dead.

Answer:

Xylem is a conducting tissue in plants. It transports water and minerals, which are absorbed from the soil by the roots of the plants, to various parts of the plant such as stems, leaves and flowers. 
The two kinds of cells in xylem tissue are xylem vessels and tracheids. Both of these cells are dead cells.

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Question 31:

What is phloem tissue? Phloem contains two types of cells joined side by side. Name these two types of cells. State whether these cells are living or dead.

Answer:

Phloem is a conducting tissue in plants. It transports the food made in the leaves to all the parts of the plant like branches, roots and stems.   
Phloem contains two types of cells, i.e. sieve tubes and companion cells. Both of these cells are living cells.

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Question 32:

(a) What is transpiration?
(b) What do you mean by 'translocation' with respect to transport in plants?
(c) Which plant tissue is involved in translocation : xylem or phloem?

Answer:

(a) The evaporation of water from the leaves of a plant in the form of water vapour is called transpiration.
(b) The transport of food from the leaves to other parts of the plant is called translocation.
(c)  Phloem translocates the food made in the leaves.

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Question 33:

(a) Draw a labelled diagram of (i) a xylem vessel, and (ii) a sieve tube (or phloem).
(b) What are the differences between the transport of materials in xylem and phloem?

Answer:

(a) Structure of a xylem vessel


 
Structure of sieve tube (or phloem)


(b) Difference between transport of materials in xylem and phloem:
 

Transport of materials in xylem Transport of materials in phloem
Xylem involves the transport of water and minerals from the soil via roots to the rest of the plant body.     Phloem involves transport of food materials from the leaves to different parts of the plant body.
Movement of water is unidirectional, i.e. upwards from the roots to the aerial parts of the plant.  Movement of food is bidirectional, i.e. both upward and downward.
Transport of material in xylem requires physical forces such as transpirational pull.   Transport of material in phloem requires energy in the form of ATP.

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Question 34:

Match the terms in column I with their uses in column II

Column I   Column II
(i) Heart (a) Pipes for transport in humans
(ii) Arteries and Veins (b) Clotting of blood
(iii) Xylem vessels (c) Pumping organ
(iv) RBC (d) Water transport in plants
(v) Platelets (e) Carrier of oxygen

Answer:

Column I Column II
(i) Heart (c) Pumping organ
(ii) Arteries and Veins (a) Pipes for transport in humans
(iii) Xylem vessels (d) Water transport in plants
(iv) RBC (e) Carrier of oxygen
(v) Platelets (b) Clotting of blood

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Question 35:

Define excretion. Name the excretory unit of a kidney.

Answer:

The process of removing waste products from the body of an organism is called excretion. The excretory unit of the kidney is nephron.

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Question 36:

(a) What job is done by the kidneys?
(b) What do kidneys excrete?
(c) What is the name of the tubes which connect the kidneys to bladder?
(d) What does the bladder in our body do?

Answer:

(a) Kidneys filter the wastes out of the blood and form the urine. They also maintain the water balance of the body.

(b) Kidneys remove the poisonous substance (urea), other waste salts and excess water from the blood, and excrete them in the form of urine.

(c) Ureters are the tubes that connect the kidneys to the bladder.

(d) The urinary bladder stores the urine until it is forced out of the body through an opening known as urethra.

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Question 37:

Why do some people need to use a dialysis machine? What does the machine do?

Answer:

The major waste products of the cells are nitrogenous wastes like ammonia and urea. Both of these compounds are toxic to the human body and must be removed from the blood regularly. The kidneys remove these wastes from the body. However, if the kidneys fail to function, the waste may accumulate and damage the internal organs of the body, which can even lead to the death of the organism. Therefore, in case of kidney failure, blood must be filtered periodically using a dialysis machine to remove the accumulated wastes from the body.
The dialysis machine cleans the blood of a person by removing the nitrogenous wastes products from it.

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Question 38:

What is the liquid part of the blood called? What is the function of platelets in the blood?

Answer:

The liquid part of the blood is called plasma. The main function of the platelets is to prevent bleeding. They contain essential chemicals that help in the coagulation of blood.

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Question 14:

Name two liquids which help in the transport of substances in the human body.

Answer:

In the human body, blood and lymph are two liquids that help in the transport of substances.

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Question 15:

What is the other name of main vein?

Answer:

The other name of the main vein is vena cava.

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Question 16:

Name the conducting tissue of plants which is made of sieve tubes alongwith companion cells.

Answer:

Phloem is the conducting tissue of plants that is made of the sieve tubes along with the companion cells.

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Question 17:

Name the conducting tissue in plants which is made of (a) living cells, and (b) dead cells.

Answer:

(a) Phloem is made up of sieve tubes, which are the living cells. 
(b) Xylem is made up of xylem vessels and tracheids. Both are non-living conducting tissues, which have thick walls.

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Question 18:

State the term used for the transport of food from leaves to other parts of plant.

Answer:

The transport of food from the leaves to other parts of the plant is called translocation.

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Question 19:

Which process in a plant is accomplished by utilising energy from ATP : transport of water and minerals or transport of food?

Answer:

ATP is utilised during the loading of food made in the leaves into the sieve tubes of phloem tissue. Thus, it is used in the transport of food.

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Question 20:

Name the two types of transport systems in the human beings.

Answer:

Blood circulatory system and lymphatic system are the two types of transport systems in human beings.

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Question 21:

Name a waste gas released by the plants (a) only during the day time, and (b) only during the night time.

Answer:

(a) Oxygen is released only during daytime. This is because oxygen is produced by photosynthesis only in the presence of sunlight.
(b) Carbon dioxide is released only during the night because carbon dioxide produced during respiration in completely used up by the plant itself in photosynthesis. 

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Question 22:

Name one animal having single circulation of blood and another having double circulation.

Answer:

Human beings have double circulation, while fish have single circulation of blood.

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Question 23:

State whether the following statements are true or false:
(a) Some organisms store wastes in body parts.
(b) The value of systolic pressure is always lower than that of diastolic pressure.

Answer:

(a) True
(b) False
The value of diastolic pressure is always lower than that of the systolic pressure.

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Question 24:

Name the two parts of a plant through which its gaseous waste products are released into the air.

Answer:

The gaseous waste products of a plant are released into the air through the leaves and the stems.

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Question 25:

What happens to the glucose which enters the nephron tubule alongwith the filtrate?

Answer:

Glucose is reabsorbed into the blood through the blood capillaries surrounding the tubule.

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Question 26:

Name the two waste products of the human body which are produced in the body cells.

Answer:

The two waste products of the human body are carbon dioxide and urea.

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Question 27:

What is the role of glomerulus in the kidney?

Answer:

In the kidney, the function of glomerulus is to filter the blood passing through it.

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Question 28:

What is the the other name of 'high blood pressure'?

Answer:

High blood pressure is called hypertension.

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Question 29:

Fill in the following blanks with suitable words:
(a) Gums and resins are the .......... products of plants.
(b) Bowman's capsule and tubule taken together make a..........
(c) The organs which extract the nitrogenous wastes from the blood are ..........
(d) The extracellular fluid which always flows from body tissues to the heart is called............
(e) The ............blood cells make antibodies whereas........... blood cells help in respiration.

Answer:

(a) Gums and resins are the waste products of plants.
(b) Bowman's capsule and tubule taken together make a nephron.
(c) The organs which extract the nitrogenous wastes from the blood are kidneys.
(d) The extracellular fluid which always flows from body tissues to the heart is called lymph.
(e) The white blood cells make antibodies whereas red blood cells help in respiration.



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Question 39:

(a) How many types of blood vessels are there in the human body? Name them.
(b) Why does the heart need valves?

Answer:

(a) There are three types of blood vessels in the human body. They are arteries, veins and capillaries.
(b) Heart needs valves to regulate the flow of blood. It allows the blood to flow through the heart only in one direction.

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Question 40:

A dialysis machine contains long tubes coiled in a tank containing dialysing solution:
(i) Of what substance are the tubes made?
(ii) What does the dialysing solution contain?
(iii) Name the main waste which passes into the dialysing solution.

Answer:

(i) The tubes, which are selectively permeable membranes, are made up of cellulose.

(ii) The dialysing machine contains water, glucose and salts, which are in similar concentrations to those in normal blood.

(iii) The main waste that passes into the dialysing solution is urea.

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Question 41:

State the differences between artery, vein and capillary.

Answer:

Differences between artery, vein and capillary:
 

Arteries Veins Capillaries
Arteries are tough, thick and elastic tubes. Veins are thin-walled and  non-elastic tubes. Capillaries are very thin-walled tubes.
They have a narrow lumen.   They have a wide lumen. They have a very narrow lumen, just wide enough for a red blood cell to pass through it.
They carry blood away from the heart to the various organs of the body, at a high pressure. They transport blood towards the heart from various organs, at a low pressure. They carry blood from the arteries to the veins.
They do not have valves. They have valves to prevent backward flow of the blood. They do not have valves.
They transport only oxygenated blood (except for the pulmonary artery).   They transport only deoxygenated blood (except for the pulmonary vein). They exchange oxygen, carbon dioxide, water and salts between the blood and the surrounding tissues.

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Question 42:

(a) What are the upper parts of the heart called?
(b) What are the lower parts of the heart called?
(c) What is the name of blood vessels which connect arteries to veins?
(d) (i) Which side of the heart pumps blood into the lungs?
     (ii) Which side of the heart pumps blood into entire body (except the lungs)?

Answer:

(a) The upper parts of the heart are called atria.

(b) The lower parts of the heart are called ventricles.

(c) Capillaries are thin-walled tubes, which connect the arteries to the veins.

(d) (i) Right side of the heart pumps blood into the lungs.
(ii) Left side of the heart pumps blood to the entire body, except the lungs.

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Question 43:

(a) What are the methods used by plants to get rid of their waste products?
(b) How are waste products excreted in Amoeba?

Answer:

(a) Following are the various methods used by plants to get rid of their waste products.

  • The gaseous wastes are removed through stomata in leaves and lenticels in stems.
  • Some wastes are removed in the form of gums and resins.
  • Some of the waste products are excreted into the soil around them.
(b) Amoeba excretes excess carbon dioxide, water and ammonia. Carbon dioxide is excreted by diffusion through the cell membrane, while excess water and nitrogenous waste like ammonia is removed by the contractile vacuole.

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Question 44:

(a) What is lymph? State two major functions of lymph.
(b) What is meant by saying that the blood pressure of a person is 120/80?

Answer:

(a) Lymph is a clear, yellowish, slightly alkaline fluid, containing white blood cells in a liquid that resembles blood plasma.

Functions of lymph:

  • It helps in the defensive mechanism of the body by killing the foreign body with the help of lymphocytes and making antibodies.
  • It transports nutrients from the tissue cells to the blood, through lymphatic vessels.

(b) A reading of 120/80 means that the person has a normal blood pressure. Here, the systolic pressure is 120 mm Hg and the diastolic pressure is 80 mm Hg.

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Question 45:

What is hypertension? Why is it caused? What harm can it do?

Answer:

Hypertension is the term used for high blood pressure. It is known as a "silent killer".
High blood pressure results from the tightening (constriction) of very small arteries called arterioles. Arterioles regulate the blood flow through our body. As these arterioles constrict, the heart has to work harder to pump the blood through the smaller space. Due to this, the pressure inside the vessels grows.
A very high blood pressure can lead to the rupture of artery and internal bleeding.

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Question 46:

What are the various components of blood? State their functions.

Answer:

Following are the various components of blood:
(a) Plasma: It helps in the transport of food, carbon dioxide, wastes and salts.
(b) Erythrocytes (RBCs): They carry the oxygen from the lungs to all parts of the body.
(c) Leucocytes (WBCs): They fight infections and protect the body from foreign particles, like germs and bacteria. 
(d) Platelets: They help in the coagulation of blood by releasing the chemicals that clot blood at the site of injury or wound.

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Question 47:

With which human organ systems (or human systems) are the following associated?
(i) vena cava
(ii) glomerulus
(iii) alveoli
(iv) villi

Answer:

(i) Vena cava is associated with human circulatory system.

(ii) Glomerulus is associated with human excretory system.

(iii) Alveoli are associated with human respiratory system.

(iv) Villi are associated with human digestive system.

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Question 48:

What is meant by 'systolic pressure' and 'diastolic pressure'? What are their normal values?

Answer:

Systolic pressure is the pressure at which the blood leaves the heart through the aorta, during contraction phase.
Diastolic pressure is the minimum pressure in the arteries during the relaxation phase of the heart.

The normal systolic pressure is 120 mm Hg, while the normal diastolic pressure is 80 mm Hg. These values are written as 120/80.

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Question 49:

(a) What is meant by 'heart beat'? What is the usual heart beat rate at rest?
(b) What change occurs in heart beats if a person runs for a while? Why?

Answer:

(a) Heart beat is the rhythmic contraction and relaxation of the heart, which includes one systole (contraction phase) and one diastole (relaxation phase) of the heart. At rest, human heart usually beats 70 to 72 times per minute.

(b) A person's heart beats faster after running for a while. This is because his body needs more energy after running.
When the heart beats faster, it pumps the oxygenated blood more rapidly to the body organs, thereby providing more oxygen to our cells (for rapid respiration) to produce more energy.

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Question 50:

(a) What is blood? Why is it red?
(b) State the functions of blood in our body.
(c) Name a circulatory fluid in the human body other than blood.

Answer:

(a) Blood is a red colour connective tissue that circulates in our body. Blood has an extra-cellular matrix called plasma, where red blood cells, white blood cells and platelets float. Blood is red because of the presence of haemoglobin. Haemoglobin is a red colour pigment, found in red blood cells.

(b) Following are the functions of blood:

  • It transports oxygen from the lungs to the cells.
  • It carries carbon dioxide, a waste product, from the body cells to the lungs.
  • It fights diseases and infections.
  • It regulates the body temperature.
  • It carries hormones to different organs of the body.

(c) Other than blood, lymph is a circulatory fluid in human body.

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Question 51:

(a) What is meant by human circulatory system? Name the organs of the circulatory system in humans.
(b) Draw a diagram of the human heart and label its parts.
(c) What is meant by the terms 'single circulation' and 'double circulation'?

Answer:

(a) The organ system that is responsible for the transport of materials inside the human body is known as human circulatory system. In human beings, the organs of circulatory system are heart, arteries, veins and capillaries.

(b) Diagram of human heart:


(c) Single circulation: A circulatory system in which the blood passes through the heart only once in one complete cycle is known as single circulation. It is commonly seen in fishes.
Double circulation: A circulatory system in which the blood travels twice through the heart in one complete cycle is known as double circulation. It is commonly seen in amphibians, reptiles, birds and mammals. 

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Question 52:

Describe the working of human blood circulatory system with the help of a suitable diagram which shows all the steps involved.

Answer:

Working of human blood circulatory system:



The human blood circulatory system is composed of the heart, the blood and the blood vessels. The human heart is divided into four chambers. The upper two chambers are called right and left atrium and the lower two chambers are called the right and the left ventricles. Following are the steps involved in the blood circulation:

  1. The left atrium receives the oxygenated blood from the lungs via the pulmonary vein.
  2. When the left atrium contracts, the oxygenated blood is pumped into the left ventricle.
  3. When the left ventricle contracts, the oxygenated blood is forced into aorta, which transports the blood to all the parts of the body, except the lungs. When oxygenated blood passes through the capillaries of different organs, it gives oxygen to the body cells. Along with oxygen, blood also gives the digested food and other dissolved materials to the body cells. At the same time, carbon dioxide, which is produced as a waste material during respiration, enters into the blood.
  4. From the body tissues, the deoxygenated blood carrying carbon dioxide is pumped back to the heart, into the right atrium, by the vena cava.
  5. When the right atrium contracts, the deoxygenated blood is pumped into the right ventricle. From here, it is taken back to the lungs by the pulmonary artery for oxygenation.
  6. The oxygenated blood is again sent to the left atrium of the heart by the pulmonary vein for being circulated in the body.
  7. The whole process is repeated again and again so as the blood keeps circulating in our body and keeps circulating oxygen, digested food and other materials to all the parts of the body. This blood also keeps on removing waste products (in the form of deoxygenated blood) formed in the cells of the body.

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Question 53:

(a) Name the red pigment which carries oxygen in the blood.
(b) Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
(c) How many chambers are there in the heart of : (i) an amphibian, (ii) a mammal, and (iii) a fish?
(d) Describe the circulatory system in a fish.

Answer:

(a) Haemoglobin is the red colour pigment that carries oxygen in the blood.

(b) Mammals and birds are warm blooded animals. Their energy requirement is high since they constantly require energy to maintain their body temperature. Hence, it is necessary to separate the oxygenated and the deoxygenated blood in mammals and birds as this separation allows a highly efficient supply of oxygen to the blood cells. This is important for producing a lot of energy and for maintaining the body temperature.

(c) (i) An amphibian, such as a frog, has a three-chambered heart, with two auricles and one ventricle.
(ii) A mammal has four-chambered heart. The upper two chambers are called atria and the lower two chambers are called ventricles.
(iii) A fish has only two chambers in its heart, i.e. one auricle and one ventricle.

(d) A fish has a two-chambered heart with one auricle and one ventricle. Since both the auricle and ventricle remain undivided, only deoxygenated blood passes through it. The deoxygenated blood passes from the ventricles into the gills for oxygenation. The oxygenated blood from the gills is then passed to the body parts of the fish where oxygen is utilised and carbon dioxide enters it, thereby making the blood deoxygenated. The deoxygenated blood then returns to the heart to be pumped again into the gills for oxygenation.
Since the blood passes through the heart of the fish only once in one complete cycle of the body, the flow of blood in a fish is known as single circulation.

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Question 54:

(a) What is lymphatic system? What are its function?
(b) What is blood pressure? What are the two factors used to express the blood pressure of a person?
(c) Name the main nitrogenous waste in the human blood. How is it removed from the blood?

Answer:

(a) Lymphatic system is a network of organs, lymph nodes, lymph ducts and lymph vessels in the human body that make and move the lymph from tissues to the bloodstream.

Following are the functions of lymphatic system:

  • It collects and transports tissue fluid from the intercellular spaces in all the tissues, back to the veins in the blood stream.
  • Lymph nodes play an important role in the defence mechanism of the body by killing the germs with the help of lymphocytes present in the lymph nodes and by making antibodies.
  • They transport larger compounds like enzymes and hormones from their manufactured sites to the blood stream.
(b)   Blood pressure is the pressure at which the blood is pumped around the body by the heart. It is always expressed in the form of two factors that are called systolic pressure and diastolic pressure.
  • Systolic pressure is the pressure at which the blood leaves the heart through the aorta during the contraction phase.
  • Diastolic pressure is the minimum pressure in the arteries during the relaxation phase of the heart.
(c) The main nitrogenous waste in the human blood is urea. The kidneys remove the urea from the blood and excrete them in the form of a dilute solution called urine. 
Kidneys are the main excretory organ of the human body. There are millions of nephrons in each kidney. Each nephron contains a renal corpuscle and a renal tubule. The renal corpuscle consists of capillaries called the glomerulus, enclosed by a capsule called Bowman's capsule. The blood is filtered in the glomerulus and the filtrate travels through the renal tubules. Here, the materials needed by the body are reabsorbed, while the wastes (like urea) are collected and excreted in the urine.

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Question 55:

(a) Name the various organs of the human excretory system.
(b) Draw a neat labelled diagram of the human excretory system.
(c) What is the function of excretory system in humans?

Answer:

(a) The human excretory system consists of two kidneys, two ureters, a bladder and a urethra.

(b)  Diagram of the human excretory system:


(c) The main function of excretory system is to remove waste and harmful by-products of the normal metabolic processes from the body.

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Question 56:

(a) Describe the mechanism of urine formation in human excretory system. Draw a labelled diagram to illustrate your answer.
(b) Where is urine carried through ureters?
(c) What is urethra?

Answer:

(a) Kidneys are the main excretory organ of the human body. There are about millions of nephron in each kidney. Each nephron contains a renal corpuscle and a renal tubule. The renal corpuscle consists of capillaries called the glomerulus, enclosed by a capsule called Bowman's capsule.  The blood containing wastes (like urea) enters the glomerulus. The glomerulus filters the blood. During filtration, the filtrate (containing substances like glucose, amino acids, salts, water and urea) present in the blood travels through the renal tubule where materials needed by the body are reabsorbed, while the wastes like urea are collected and excreted in the urine. The nephron carries the urine into the collecting tubule of the kidney from where it is carried to the ureter. From the ureter, the urine passes into the urinary bladder. The urinary bladder stores the urine until it is forced out of the body, through an opening known as the urethra.

(b) Urine is carried into the urinary bladder through two narrow tubes that are called ureters.

(c) Urethra is the small opening that carries urine out of the body.

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Question 57:

(a) What is meant by dialysis? What type of patients are put on dialysis?
(b) Explain the principle of dialysis with the help of a labelled diagram.

Answer:

(a) Dialysis is the process of removing waste substances like urea from the blood, using a kidney machine. The patients who are most likely suffering from a severe ailment of excretory system are put on dialysis.

(b) Principal of dialysis:


The procedure of dialysis is based on diffusion of solutes and ultrafiltration of fluid across a semi-permeable membrane. In dialysis, the blood from a convenient artery is pumped into the dialyser of a dialysing machine. A dialyser contains a coiled cellophane tube surrounded by the dialysing solution. The dialysing solution contains water, glucose and salts, which are similar in concentration to those in normal blood. The porous cellophane membrane of the tube allows the passage of molecules based on concentration gradient. As the patient’s blood is passed through the dialysing solution, most of the wastes (like urea) present in it pass through the selectively permeable cellulose tubes into the dialysing solution, thereby cleaning the blood. The clean blood is pumped back to the body through a vein.
 
   

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Question 58:

(a) Why is transport of materials necessary in an organism (plant or animal)?
(b) What is the need of special tissues or organs for transport of substances in plants and animals?
(c) How are water and minerals transported in plants?
(d) How is food transported in plants?

Answer:

(a) Transport of materials is necessary in plants and animals as every cell needs a regular supply of nutrients and oxygen to provide energy during respiration.

(b) Organisms like plants and animals need special tissues and organs for the transport of substances because tissues and organs can easily transport the essential substances like food, oxygen and water from one part of the body to another.  For example, the xylem tissues of roots, stems and leaves are interconnected and form a continuous network of channels to transport water to all parts of the plant body.

(c) Water and minerals are absorbed by the cells of the root hair. The root hair is in direct contact with the water present between the soil particles. As the water is absorbed by the roots from the soil, it is transported to various parts of the plants through the xylem tubes. Water is mainly pulled from the leaves by transpiration. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then, there is a steady movement of water from the root xylem to all the parts of the plant, through interconnected water conduction elements. 

(d) The transport of food from the leaves to the other parts of the plant occurs through the vascular tissue called phloem. The food (sugar) made in leaves is loaded into the sieve tubes of phloem tissue by using the energy derived from ATP. As a result, the osmotic pressure in the tissue increases, causing the water to move into it. This high pressure produced in the phloem, moves the food to all the parts of the plant that have less pressure in their tissues. This process is helpful in moving the food materials according to the needs of the plant.



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Question 59:

One of the following does not have a nucleus. This one is:
(a) red blood cell
(b) white blood cell
(c) guard cell
(d) epidermal cell

Answer:

(a) red blood cell
Red blood cells do not have nuclei.

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Question 60:

The component of blood which makes chemicals known as antibodies is:
(a) platelets
(b) white blood cell
(c) red blood cells
(d) plasma

Answer:

(b) white blood cells
White blood cells make chemicals known as antibodies that help to fight against infection and protect the body from foreign particles.

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Question 61:

An animal in which the oxygenation of blood does not take place in the lungs is:
(a) cow
(b) fish
(c) frog
(d) fox

Answer:

(b) fish
The aquatic animals like fish have gills as their respiratory organs. Gills extract oxygen dissolved in water and take away carbon dioxide from the body.
On the other hand, cow, frog and fox, breathe through lungs.

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Question 62:

Which of the following carries substances upwards as well as downwards in a plant?
(a) xylem
(b) companion cells
(c) phloem
(d) tracheids

Answer:

(c) phloem
In a plant, phloem carries substances (food) upwards as well as downwards.

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Question 63:

One of the following is not a constituent of blood. This one is:
(a) red blood cells
(b) white blood cells
(c) sieve plates
(d) platelets

Answer:

(c) sieve plates
Sieve plates do not constitute blood. They are a part of phloem.

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Question 64:

If a patient is put on dialysis, he is most likely suffering from a severe ailment of the:
(a) circulatory system
(b) respiratory system
(c) excretory system
(d) digestive system

Answer:

(c) excretory system
Dialysis is the process of removing wastes using an artificial kidney. Hence, if a patient is out on dialysis, he is most likely suffering from a severe ailment of excretory system. It is because kidneys are a part of human excretory system and in case of kidney failure, to remove the accumulated wastes from the body, blood is filtered periodically through an artificial kidney.

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Question 65:

Water absorption through roots can be increased by keeping the potted plants:
(a) in the shade
(b) in dim light
(c) under the fan
(d) covered with a polythene bag

Answer:

(c) under the fan
Water absorption through roots can be increased by keeping the potted plants under the fan.

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Question 66:

A blood vessel which carries blood back to the heart is:
(a) artery
(b) vein
(c) capillary
(d) platelet

Answer:

(b) vein
Veins carry carbon dioxide rich blood from the various tissues of the body to the heart.

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Question 67:

Blood is pumped from the heart to the entire body by the:
(a) lungs
(b) ventricles
(c) atria
(d) nerves

Answer:

(b) ventricles
Ventricles pump oxygenated blood from the heart to the entire body.

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Question 68:

The blood leaving the tissues becomes richer in:
(a) carbon dioxide
(b) water
(c) haemoglobin
(d) oxygen

Answer:

(a) carbon dioxide
The blood leaving the tissues becomes richer in carbon dioxide, i.e. it becomes deoxygenated.

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Question 69:

What prevents the backflow of blood inside the heart during contraction?
(a) thick muscular walls of ventricles
(b) valves
(c) thin walls of atria
(d) all of the above

Answer:

(b) valves

During contraction, valves prevent the back-flow of blood inside the heart.

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Question 70:

Which of the following is the correct path taken by urine in our body?
(a) kidney → ureter → urethra → bladder
(b) kidney → bladder → urethra → ureter
(c) kidney   → ureter → bladder → urethra
(d) bladder → kidney → ureter → urethra

Answer:

 (c) kidney → ureter → bladder → urethra

During blood circulation, blood passes through the kidneys. This blood contains both useful and waste materials. The kidneys filter the wastes from the blood and produce urine. From the kidneys, the urine goes into the urinary bladder through two narrow tubes called ureters. The urinary bladder stores the urine until it is forced out of the body, through an opening known as the urethra.

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Question 71:

In which of the following vertebrate group/groups, heart does not pump oxygenated blood to different parts of the body?
(a) pisces and amphibians
(b) amphibians and reptiles
(c) amphibians only
(d) pisces only

Answer:

(d) Pisces only
In Pisces, the heart does not pump oxygenated blood to different parts of the body. This is because Pisces have two-chambered heart with one auricle and one ventricle. Since both the auricle and ventricle remain undivided, only deoxygenated blood passes through it. The deoxygenated blood then enters the gills for oxygenation from the ventricle.

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Question 72:

Which vein brings clean blood from the lungs into the heart?
(a) renal vein
(b) pulmonary vein
(c) vena cava
(d) hepatic vein

Answer:

(b) pulmonary vein
Pulmonary vein carries oxygenated blood (clean blood) from the lungs into the heart.

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Question 73:

Which blood vessel does not carry any carbon dioxide?
(a) pulmonary artery
(b) vena cava
(c) hepatic vein
(d) pulmonary vein

Answer:

(d) pulmonary vein
Pulmonary vein carries the oxygen rich blood from the lungs to the heart.

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Question 74:

It has been found that people living in very high mountains have many more red corpuscles in their blood than people living in plains. Which one of the following best accounts for this phenomenon?
(a) the cold climate stimulates the production of red corpuscles to keep the body warm
(b) people of high mountains breathe more quickly
(c) the low air pressure requires more red corpuscles to supply the body cells with oxygen.
(d) the low air pressure in high mountains speeds up the blood circulation so that more red corpuscles are needed

Answer:

(c) the low air pressure requires more red corpuscles to supply the body cells with oxygen.

At high altitude, the atmospheric pressure of oxygen is low. As a result, the number of red blood cells in the body cannot meet the cell's demands for oxygen.  Therefore, the body increases its red blood cell count in order to supply more oxygen to the body cells, even with less oxygen in the atmosphere. Hence, people living on very high mountains have more red corpuscles in their blood than those living in plains.

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Question 75:

The phloem tissue in plants is responsible for the transport of:
(a) water
(b) water and minerals
(c) sugar
(d) all of the above

Answer:

(c) sugar
In plants, the phloem tissue is responsible for the transport of food (in the form of sugar) from the leaves to different parts of the body.

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Question 76:

Which of the following has a three-chambered heart?
(a) pigeon
(b) lizard
(c) fish
(d) lion

Answer:

b) lizard
Lizard is a reptile and it has a three-chambered heart. Birds (e.g. Pigeon) and mammals (e.g. lion) have a four-chambered heart, while Pisces (e.g. fish) have a two-chambered heart.



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Question 77:

In which of the following are the largest amounts of nitrogen excreted from a mammalian body?
(a) breath
(b) sweat
(c) urine
(d) faeces

Answer:

 (c) urine
The largest amount of nitrogen is excreted from a mammalian body as urine.

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Question 78:

Which one of the following has cytoplasm but no nucleus:
(a) xylem vessel
(b) sieve tube
(c) tracheid
(d) companion cell

Answer:

(b) sieve tube
Sieve tube, which forms the phloem, are living cells containing cytoplasm but no nucleus.

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Question 79:

The process of carrying food from the leaves to other parts of a plant is called:
(a) transpiration
(b) transportation
(c) translocation
(d) transformation

Answer:

(c) translocation
The process of carrying food from the leaves to other parts of a plant is called translocation.

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Question 80:

Which of the following is the only conducting tissue in non-flowering plants?
(a) xylem vessels
(b) sieve tubes
(c) companion cells
(d) tracheids

Answer:

 (d) tracheids
Tracheids are the only conducting tissue in non-flowering plants.

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Question 81:

Which of the following helps in the upward movement of water and dissolved minerals from the roots to the leaves through the stem?
(a) transportation
(b) translocation
(c) tropic movement
(d) transpiration

Answer:

(d) transpiration
Transpiration is the loss of water through the stomata of leaves and other aerial parts of the plants in the form of water vapour. It provides a transpirational pull, which is responsible for the upward movement of water and dissolved minerals from the roots to the leaves through the stem.

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Question 82:

Which one of the following does not have valves?
(a) heart
(b) arteries
(c) capillaries
(d) veins

Answer:

(c) capillaries
Capillaries do not have valves, while heart and veins have valves to prevent the back-flow of blood.

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Question 83:

Which of the following is accomplished in a plant by utilising the energy stored in ATP?
(a) transport of food
(b) transport of water and minerals
(c) transport of oxygen
(d) transport of water, minerals and food

Answer:

(a) transport of food
The translocation (transport of food) in phloem takes place by utilising the energy stored in the ATP molecules. It takes place in the sieve tubes with the help of adjacent companion cells, both in upward and downward direction.

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Question 84:

Coagulation of blood in a cut or wound is brought about by:
(a) plasma
(b) platelets
(c) WBC
(d) RBC

Answer:

(b) platelets
Platelets release chemicals responsible for blood clotting at the site of a cut or a wound. These chemicals help in the coagulation of blood. The main function of the platelets is to form clot and prevent bleeding.

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Question 85:

The blood vessel which carries oxygenated blood from the lungs to the heart is:
(a) main artery
(b) pulmonary artery
(c) main vein
(d) pulmonary vein

Answer:

(d) pulmonary vein
Veins transport deoxygenated blood from various organs of the body towards the heart. Only pulmonary vein carries the oxygenated blood from the lungs to the heart.

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Question 86:

The instrument for measuring blood pressure is called:
(a) manometer
(b) sphygmomanometer
(c) barometer
(d) potentiometer

Answer:

(b) sphygmomanometer
The device used for measuring blood pressure is called sphygmomanometer.

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Question 87:

The excretory unit in the human excretory system is called:
(a) nephron
(b) neuron
(c) nephridia
(d) kidneyon

Answer:

(a) nephron
The main excretory unit in the human excretory system is called nephron. It produces urine and maintains the homeostasis of the body. 

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Question 88:

The substance which is not reabsorbed into the blood capillaries surrounding the tubule of a nephron is mainly:
(a) glucose
(b) amino acid
(c) urea
(d) water

Answer:

(c) urea
Urea is not reabsorbed into the blood capillaries that surround the tubule of a nephron. However, glucose, amino acid and water are reabsorbed.

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Question 89:

The procedure of cleaning the blood of a person by using a kidney machine is known as:
(a) ketolysis
(b) hydrolysis
(c) dialysis
(d) photolysis

Answer:

(c) dialysis
The process of removing wastes (urea) from the blood using a kidney machine is known as dialysis.

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Question 90:

The excretory organs in an earthworm are:
(a) nephridia
(b) nephrons
(c) raphides
(d) ureters
 

Answer:

(a) nephridia
In earthworm, the main excretory organs are nephridia. It functions like a kidney.

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Question 91:

The cells in our blood which destroy disease-causing germs, are:
(a) platelets
(b) skin cells
(c) RBCs
(d) WBCs

Answer:

(d) WBCs
White blood cells or WBCs destroy the disease causing germs. They are like soldiers that protect the body from various infections.

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Question 92:

The wave of expansion of an artery when blood is forced into it is called:
(a) flow
(b) heart beat
(c) pulse
(d) ticking

Answer:

(c) pulse
Pulse is the expansion of the artery each time the blood is forced into it.

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Question 93:

In autotrophs, water is transported through:
(a) root hair
(b) phloem
(c) stomata
(d) xylem

Answer:

(d) xylem
Xylem transports water and minerals from the soil via the roots to the rest of the plant body.

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Question 94:

An animal having double circulation in a three-chambered heart is:
(a) fish
(b) snake
(c) deer
(d) sparrow

Answer:

(b) snake
Snake is a reptile and has a double circulation in a three-chambered heart. Pisces (e.g. fish) has a single circulation in a two-chambered heart, while mammals (e.g. deer) and birds (e.g. sparrow) have a double circulation in a four-chambered heart.

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Question 95:

The transport system in plants consists of two kinds of tissues X and Y. The tissue X is made up of living cells and consists of two components A and B. The component A has tiny pores in its end walls and contains only cytoplasm but no nucleus. On the other hand, component B has cytoplasm as well as nucleus. The tissue Y is made up of dead cells and consists of two components C and D. The component C has open ends whereas component D does not have open ends. In flowering plants, either only C or both C and D transport water but D is the only water conducting tissue in non-flowering plants.
(a) What is (i) tissue X (ii) component A, and (iii) component B?
(b) What is (i) tissue Y (ii) component C, and (iii) component D?

Answer:

(a)
(i) The tissue X is phloem. Phloem is made of living cells and helps in the transport of food from leaves to other parts of the body.

(ii) A sieve tube, which forms the phloem, has tiny pores in its end walls and contains only cytoplasm. It does not have any nucleus. Hence, component A is a sieve tube.
(iii) Companion cell is a component of phloem and has cytoplasm as well as nucleus. Hence, component B is a companion cell.

(b)
(i) Tissue Y is xylem. It is made of dead cells and helps in the transport of water and minerals from the soil via roots to the rest of the plant body.
(ii) Xylem vessel is a component of xylem and has open ends. Hence, component C is xylem.
(iii) Tracheid does not have open ends. Hence, component D is a tracheid.

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Question 96:

Water and dissolved minerals get into the root hair of a plant by a process called A and enter the conducting tissue B. The process C helps the water and dissolved minerals to move up through the tissue B in roots and stem, and reach the leaves of a plant. In the leaves food is made by a process D. This food is then transported to all the parts of a plant through tissue E. The process of distributing food made in the leaves to all the parts of the plants is called F.
(a) What are (i) A (ii) B (iii) C (iv) D (v) E, and (vi) F?
(b) Which tissue is made up of living cells : B or E?
(c) Which tissue, B or E, contains sieve tubes?
(d) Which tissue, B or E, contains tracheids?

Answer:

(a)
(i) The process by which water and dissolved minerals get into the root hair of a plant is known as diffusion. Hence, A is diffusion. 
(ii)
The water and dissolved minerals are absorbed by the cells of the root hair, which enter the conducting tissue known as xylem. Hence, B is xylem.
(iii) Transpiration helps in transporting water and dissolved minerals to move up through the xylem tissue (B) in the roots and the stem, and reach the leaves of a plant. Hence, C is transpiration.
(iv) In leaves, the food is prepared by a process known as photosynthesis. Hence, the process D is photosynthesis.
(v) The food synthesised by the leaves of a plant is transported to all the parts of a plant through tissue phloem (E). Hence, E is phloem.
(vi) The process of distributing (or transporting) food made in the leaves to all the parts of the plant is called translocation. Hence, F is translocation. 

(b) B represents xylem, while E represents phloem. Out of these, phloem (E) is made of living cells.

(c) E (phloem) contains sieve tubes.

(d) B (xylem) contains tracheids.



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Question 97:

The liquid connective tissue A circulates in our body continuously without stopping. This tissue contains a pigment B which imparts it a colour C. The tissue A consists of four components D, E, F and G. The component D fights infection and protects us from diseases. The component E helps in the clotting of tissue A if a person gets a cut. The component F is a liquid which consists mainly of water with many substances dissolved in it and component G carries oxygen from the lungs to all the parts of the body.
(a) What is (i) tissue A (ii) pigment B, and (iii) colour C?
(b) Name (i) D (ii) E (iii) F, and (iv) G.
(c) Name one substance (other than oxygen) which is transported by tissue A in the human body.
(d) Which two components of tissue A are the cells without nucleus?
(e) Name any two organisms ( animals) which do not have liquid like A in their body.

Answer:

(a)
(i) Blood is the liquid connective tissue that circulates in our body continuously without stopping. Hence, A is blood.
(ii) & (iii) Our blood contains a pigment called haemoglobin, which imparts it a red colour. Hence, pigment B is haemoglobin and colour C is red.

(b)
(i) White blood cells, fight infection and protect us from diseases. Hence, D refers to white blood cells.
(ii) Platelets are the component of blood, which help in the clotting of blood (A). Hence, E refers to platelets.
(iii) Plasma is a liquid, which consists mainly of water with many substances dissolved in it. Hence, F refers to plasma.
(iv) Red blood cells carry oxygen from the lungs to all the parts of the body. Hence, G refers to red blood cells.

(c) Blood also carries the digested food from the small intestine to all other parts of the body.

(d) E (platelets) and G (Red blood cells) are the cells without nucleus.

(e) Amoeba and grasshopper do not have blood (A) like liquid in their body.

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Question 98:

The human body has an organ A which acts as a double pump. The oxygenated blood coming from the lungs through a blood vessel B enters the upper left chamber C of the double pump. When chamber C contracts, then blood goes into lower left chamber D. The contraction of chamber D forces the blood to go into a blood vessel E which supplies oxygenated blood to all the organs of the body (except the lungs). The deoxygenated blood coming out of the body organs is taken by a blood vessel F to the right upper chamber G of pumping organ. Contraction of chamber G forces the deoxygenated blood into right lower chamber H. And finally the contraction of chamber H sends the deoxygenated blood into lungs through a blood vessel I.
(a) What is organ A?
(b) Name the blood vessel (i) B (ii) E (iii) F, and (iv) I.
(c) What are chambers (i) C, and (ii) D?
(d) What are chambers (i) G and (ii) H?

Answer:

(a) Heart is the organ in the human body that acts as a double pump. Hence, organ A represents the heart.

(b)
(i) The oxygenated blood from the lungs enters the left atrium (chamber C) via the blood vessel called pulmonary vein (B). Hence, B is pulmonary vein.
(ii) The contraction of left ventricle (chamber D) forces the blood into the blood vessel called aorta (E), which supplies the oxygenated blood to the organs of the body, except the lungs. Hence, E is aorta.
(iii) From the body tissues, the deoxygenated blood is transported back to the heart into the right upper chamber called right atrium (G), by the vena cava (F). Hence, F is vena cava.
(iv) Contraction of chamber G (right atrium) forces the deoxygenated blood into the lower right chamber called right ventricle (H). Finally, the contraction of H (right ventricle), sends the deoxygenated blood into the lungs through the blood vessel called pulmonary artery (I). Hence, I represent pulmonary artery.

(c)
(i) The chamber C represents left atrium. 
(ii) The chamber D represents left ventricle.

(d)
(i) The chamber G represents right atrium.
(ii) The chamber H represents right ventricle.

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Question 99:

A liquid X of colour Y circulates in the human body only in one direction : from body tissues to the heart. Among other things, liquid X contains germs from cells and dead cells. The liquid X is cleaned of germs and dead cells by a special type of white blood cells called Z. This cleaned liquid is then put into blood circulatory system in subclavian veins.
(a) What is (i) liquid X, and (ii) colour Y?
(b) What are Z?
(c) The liquid X is somewhat similar to a component of blood. Name this component.
(d) Why is liquid X not red?

Answer:

(a) Lymph (X) is a light yellow colour (Y) liquid that circulates in the human body. It circulates from the body tissues to the heart. Hence, (i) the liquid X is lymph. (ii) The colour Y is light yellow.

(b) The liquid X (lymph) is cleaned of germs and dead cells by a special type of white blood cells called lymphocytes (Z). Lymphocyte helps in fighting infections and diseases. Thus, Z represents lymphocytes.

(c)The liquid X, i.e. lymph, is somewhat similar to plasma.

(d) The liquid X, i.e. lymph, is not red because it does not contain red blood cells that have red colour pigment called haemoglobin.

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Question 100:

There is a pair of bean-shaped organs P in the human body towards the back, just above the waist. A waste product Q formed by the decomposition of unused proteins in the liver is brought into organ P through blood by an artery R. The numerous tiny filters S present in organ P clean the dirty blood by removing the waste product Q. The clean blood goes into circulation through a vein T. The waste substance Q, other waste salts, and excess water form a yellowish liquid U which goes from organ P into a bag-like structure V through two tubes W. This liquid is then thrown out of the body through a tube X.
(a) What is (i) organ P, and (ii) waste substance Q?
(b) Name (i) artery R, and (ii) vein T.
(c) What are tiny filters S known as?
(d) Name (i) liquid U (ii) structure V (iii) tubes W, and (iv) tube X.

Answer:

(a)
(i)  Kidneys are bean shaped organs in the human body, towards the back of the body, just above the waist. Hence, organs P are kidneys.
(ii)  Urea is the waste product that is formed by the decomposition of unused proteins in the liver. Hence, the waste substance Q represents urea. 

(b)
(i) Urea (substance Q) is brought into kidney (organ P) through blood by an artery called renal artery. Hence, R represents renal artery.
(ii) The numerous tiny filters called nephrons (S) present in the kidneys (organ P), clean the dirty blood by removing the waste product Q (urea). The clean blood then goes into circulation through T, i.e. renal vein. Hence, vein T represents the renal vein.

(c) The tiny filters S are known as nephrons.

(d) The waste substance Q (urea), other waste salts and excess water form a yellowish liquid called urine (U). Urine goes from organ P (kidney) into a bag-like structure V, i.e. urinary bladder, through two tubes W, called ureters. This urine is then thrown out of the body     through tube X, called urethra.
Hence, (i) the liquid U is urine, (ii) structure V is urinary bladder, (iii) tubes W is ureters, and (iv) tube X is the urethra.

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Question 101:

The organs A of a person have been damaged completely due to which too much of a poisonous waste material B has started accumulating in his blood, making it dirty. In order to save this person's life, the blood from an artery in the person's arm is made to flow into long tubes made of substance E which are kept in coiled form in a tank containing solution F. This solution contains three materials G, H and I in similar proportions to those in normal blood. As the person's blood passes through long tubes of substance E, most of the wastes present in it go into solution. The clean blood is then put back into a vein in the arm of the person for circulation.
(a) What are organs A?
(b) Name the waste substance B.
(c) What are (i) E, and (ii) F?
(d) Name G, H and I.
(e) What is the process described above known as?

Answer:


(a) Organ A is kidney. Complete damage of the kidney (organ A) can lead to the accumulation of waste material B, i.e. urea, in the blood.

(b) The waste substance B is urea.

(c)
(i) In dialysis, the blood from a convenient artery is pumped into the dialyser of a dialysing machine. The dialyser contains a coiled cellophane tube made of substance E, called cellulose. It is surrounded by the dialysing solution (F). Hence, E represents cellulose.
(ii) F represents the dialysing solution.
 
(d)  The dialysing solution contains water (G), glucose (H) and salts (I), which is similar in concentration to those in normal blood.

(e) The process of removing waste substances like urea from the blood using a kidney machine
is known as dialysis.



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