Basic Science Solutions for Class 7 Science Chapter 9 Obtaining And Utilising Food are provided here with simple step-by-step explanations. These solutions for Obtaining And Utilising Food are extremely popular among Class 7 students for Science Obtaining And Utilising Food Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Basic Science Book of Class 7 Science Chapter 9 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Basic Science Solutions. All Basic Science Solutions for class Class 7 Science are prepared by experts and are 100% accurate.

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Three life processes that help living organisms to procure energy from food are:
(i) Digestion (Nutrition)
(ii) Respiration
(iii) Transportation

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Autotrophs are organisms that can prepare their own food. Chlamydomonas, a type of green algae, is an example of an autotroph, other than green plants.

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Three types of heterotrophic nutrition are:
(i) Saprophytic nutrition
(ii) Parasitic nutrition
(iii) Holozoic nutrition

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Enzymes are chemical substances that act as biological catalysts and are important for carrying out biochemical processes, such as digestion, in our body.

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Holozoic nutrition involves the following steps:
(i) Ingestion
(ii) Digestion
(iii) Absorption
(iv) Assimilation
(v) Egestion

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Green plants require the following three things to prepare their food:
(i)  Carbon dioxide (CO2)
(ii) Water (H2O)
(iii) Sunlight

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Juice secreted by the liver is called bile. It helps in digestion of fats by breaking them down into small droplets.

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Cuscuta is a parasitic plant. Ascaris is a parasite that inhabits in our intestines.

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Digestion is the process of taking in nutrients and breaking them down, physically and chemically, into simpler form so that they could be absorbed.

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Spider is a holozoic organism but not a herbivore or a carnivore or an omnivore.

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Saprophytes: Saprophytes are the organisms that feed on dead and decaying organic matter. Example: Bread mould (a fungi)
Parasites : Parasites are organisms that derive their nutrition from other animals or plants by living inside their body or on it. Example: Round worm

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Herbivores feed on green plants, which are difficult to chew and digest due to cellulose in them. Most of the teeth of herbivores are on the side of their jaws to help them powerfully chew grass and leaves. They have incisors in the front to help them cut the grass.

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Amoeba
is a unicellular holozoic organism. It is an omnivore that feeds on smaller unicellular organisms or their fragments. It forms two finger-like projections called pseudopodia around the food particle. These projections fuse at the tip, thereby, completely engulfing the food. In the end, they fuse with each other to form a food vacuole, where the food gets digested.

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Carnivore plants are found at places where nitrogen is deficient in soil. They trap insects and digest them to fulfil their protein and nitrogen requirements.
For example, sundews secrete sticky substance on their leaves. Insects confuse droplets of this fluid with dew and get attracted by them and sit on the leaves. The hair on these leaves traps the insects and suffocate them as soon as they approach the leaves.

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Symbionts are organisms that live together for mutual benefits. An example of symbiont is nitrogen-fixing bacteria. They live in the root nodules of plants and fix atmospheric nitrogen into biologically absorbable form, which is useful for plants. They fix nitrogen for plants and plants in turn protect them.

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Dr. Beaumont, while treating one of his patients St. Martin, who was accidently hit by a bullet in the stomach, found that after 18 months of treatment, a hole was left in St. Martin's stomach  even though the wound had healed. When Dr. Beaumont experimented with the food from St. Martin's stomach for nine years, he found that digestion occurs in the stomach due to the action of juices, secreted by the stomach, on the food we eat.

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Digestive juice in the mouth is called saliva. Saliva contains salivary amylase or ptylin. This is an enzyme that acts upon complex carbohydrates (sugars) such as starch to convert them into simpler carbohydrates such as maltose. Thus, saliva helps in partial digestion of carbohydrates.

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The alternate relaxation and contraction of organs made of smooth muscles in our body is called peristalsis. In oesophagus, as the food enters, a part of oesophagus, just above the food particle, contracts and sends the food downward. The part just below this contracted part now contracts and the part that earlier contracted now gets relaxed.
No, it occurs in the whole alimentary canal and not just in oesophagus.



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The juice produced in the stomach contains hydrochloric acid and an enzyme called pepsin. As the food moves to the stomach, this digestive juice in the stomach is released. Hydrochloric acid kills the bacteria and other pathogens, and pepsin helps in the digestion of proteins.

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The undigested food and germs from the large intestine are thrown out of the body via the anus in the form of semi-solid waste, after absorption of some amount of water.

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Take a leaf and put it in a test tube, half filled with alcohol. The leaf should be submerged in the alcohol in such a way that half of it remains outside. Put the test tube in a beaker filled with water and heat it. Direct heating of the test tube containing alcohol should be avoided as it may catch fire.
The part of leaf submerged in the alcohol will start losing colour, as alcohol destroys its green pigment, chlorophyll. When this half leaf loses its colour completely, pull out the leaf and wash it gently to remove alcohol. After a few minutes, put some drops of iodine on the green and non-green halves.
 Observation: It is observed that the green part changes its colour to blue-black on dropping iodine. This indicates the presence of starch. The green pigment synthesises starch by trapping energy and gives blue-black colour on reaction with iodine. The colourless part of the leaf gives no such result. Thus, it is confirmed that presence of chlorophyll is a must for photosynthesis to take place.

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Complete digestion and absorption of food occur in the small intestine. As the food enters the small intestine, it is acted upon by a number of digestive juices secreted by the liver, pancreas and walls of small intestine.
Bile is a pigment secreted by the liver that acts upon fat and breaks it into smaller pieces to make it easily digestible. The juices secreted by pancreas contain several enzymes that act upon carbohydrates and proteins to digest them completely. Walls of small intestine also secrete several enzymes to complete the digestion.
The walls of small intestine are not smooth. They are rough due to the presence of a number of miniature finger-like projections called villi, which help in increasing the surface area of the small intestine. This in turn helps in efficient absorption of digested food.

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An adult human has 32 teeth arranged in the upper and lower jaws. These teeth masticate food and break it into small pieces. This provides an even texture to the food and makes it easily digestible.
We have four kinds of teeth in our oral cavity or mouth. They are:
(i) Incisors : They are flat teeth that act like scissors. They help in cutting food.
(ii) Canines:  These are sharp teeth and are very prominent in carnivores. They are pointed and help in tearing food. They function like knives in carnivores and help them capture their prey.
(iii) Premolars: These are teeth having broad surface. They help in grinding and chewing food.
(iv) Molars : They also help in grinding the food and chewing it. They are larger than premolars.

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The stomach of a ruminant (grass eating herbivores) is divided into four chambers and is capable of digesting cellulose. Ruminants chew the grass and other vegetable materials partially before swallowing it. This half or partially chewed food goes to the first chamber of the stomach, where the residing bacteria digest the cellulose. The first and second chambers break the food into smaller pieces and digest the cellulose. This half digested food is sent back to the mouth for re-chewing. This re-chewing of half digested food is called cud chewing or rumination. Ruminants derive their name from this process. When this food is swallowed again, it goes to the third chamber, where water and minerals are absorbed and further digestion takes place. Complete digestion takes place in the fourth chamber, where enzymes completely digest the food.

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1. The tubelike mouthpart of a butterfly is called a proboscis.
2. The process by which digested food enters the blood is called absorption.
3. Chemical substances produced in the body of an organism to help in the process of digestion are called enzymes.
4. The tube, starting from the mouth and ending in the anus, through which food passes is called the alimentary canal.
5. Digestion begins in the mouth.
6. The fingerlike folds in the wall of the small intestine are called villi.

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(c) depend on sources other than themselves for food
Heterotrophs are organisms that depend on sources other than themselves for food.

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(a) blue-black
Iodine turns starch blue-black.

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(a) water
Walls of large intestine absorb water.

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(c) digested food is utilised by the body
Assimilation is the process by which digested food is utilised by the body.

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(d) undigested sugar
Cellulose is a type of sugar which remains undigested in the human body.

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(d) starch
Plants store food as starch.



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