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Page No 29:

Question 1:

The rising of dough while making bread is due to the
(a) heat produced in it.
(b) CO2 produced as a result of fermentation.
(c) multiplication of yeast cells.
(d) kneading.

Answer:

(b) CO2 produced as a result of fermentation

Carbon dioxide produced as a result of fermentation makes the dough rise while making bread.

Page No 29:

Question 2:

Which one of the following is a plant disease?
(a) rust
(b) ringworm
(c) scabies
(d) cholera

Answer:

(a) rust

Rust is a disease that damages wheat.

Page No 29:

Question 3:

Which one of the following is not caused by a fungus?
(a) rust
(b) scabies
(c) hepatitis
(d) athlete's foot

Answer:

(c) hepatitis

Hepatitis is caused by virus.



Page No 30:

Question 4:

Which one of the following is not an example of a fungus?
(a) mushroom
(b) Spirogyra
(c) yeast
(d) mould

Answer:

(b) Spirogyra

It is an algae.

Page No 30:

Question 5:

The vector for malaria is ___________.
(a) Anopheles
(b) Amoeba
(c) bacteria
(d) fungus

Answer:

(a) Anopheles

Malaria is carried by female Anopheles mosquitoes.

Page No 30:

Question 6:

An example of nitrogen fixing bacteria is
(a) Nostoc.
(b) spirilla.
(c) bacillus.
(d) comma.

Answer:

(a) Nostoc

​Nostoc is an example of nitrogen fixing bacteria.

Page No 30:

Question 7:

Atmospheric nitrogen is fixed by
A. all algae.
B. Rhizobium.
C. all bacteria.
D. lightning.

(a) Only B is correct.
(b) Only C is correct.
(c) All are correct.
(d) Both B and D are correct.

Answer:

(d) Both B and D are correct.

Atmospheric nitrogen is fixed by Rhizobium bacteria as well as by lightening.

Page No 30:

Question 8:

Plant-like protists are so called because
(a) they look like plants.
(b) they carry out all functions like plants.
(c) they posses chlorophyll like plants.
(d) all of the above.

Answer:

(c) they possess chlorophyll like plants

They have chlorophyll; therefore, they can prepare their own food.

Page No 30:

Question 9:

Like bacteria, Amoeba also undergoes reproduction by
(a) budding.
(b) spores.
(c) fission.
(d) conjugation.

Answer:

(c) Fission

Amoeba and bacteria undergo reproduction by binary fission.

Page No 30:

Question 10:

Pasteurisation is a method used to preserve milk by
(a) lowering the temperature of the milk.
(b) destroying the harmful bacteria.
(c) lowering the fat content of the milk.
(d) none of the above.

Answer:

(b) destroying the harmful bacteria

In this process, milk is heated to 72°C for 15 seconds and then immediately cooled to kill the harmful bacteria.

Page No 30:

Question 11:

Which one of the following is not a fungal disease that affects human being?
(a) athlete's foot
(b) rust
(c) scabies
(d) ringworm

Answer:

(b) rust

Rust is a disease that affects wheat. The other three diseases affect human beings.

Page No 30:

Question 12:

Which of the following is not paired correctly?
(a) yeast : fermentation
(b) coccus : rod-shaped
(c) bread mould : spores
(d) bacteria : decomposers

Answer:

(b) coccus : rod-shaped

Coccus are the spherical bacteria. Rod-shaped bacteria are known as Bacilli.

Page No 30:

Question 13:

An example of a plant-like protist is
(a) Amoeba.
(b) paramecium.
(c) diatom.
(d) plasmodium.

Answer:

(c) Diatom

Diatom is a plant-like protist that contains chlorophyll.

Page No 30:

Question 14:

An example of a blue-green bacterium is
(a) Nostoc.
(b) bacillus.
(c) coccus.
(d) spirilla.

Answer:

(a) Nostoc

​Nostoc is an example of a blue-green bacterium.

Page No 30:

Question 15:

Which of these diseases is not caused by bacteria?
(a) cholera
(b) hepatitis
(c) tuberculosis
(d) typhoid

Answer:

(b) Hepatitis

Hepatitis is caused by virus.

Page No 30:

Question 16:

The rising of dough in making dosa is an example of
(a) pasteurisation.
(b) maturing.
(c) curing.
(d) fermentation.

Answer:

(d) fermentation

Fermentation is carried out by yeasts (fungi), which causes the rising of dough while making dosa.

Page No 30:

Question 17:

Which of the following is not used for preserving food?
(a) freezing
(b) smoking
(c) fermentation
(d) pickling

Answer:

(c) fermentation

The other three processes are used for preserving food.

Page No 30:

Question 18:

In what ways are fungi useful to us?

Answer:

Fungi are useful to us in the following ways:
1) Yeast helps in making bread soft.
2) Penicillium produces an antibiotic called penicillin.

Page No 30:

Question 19:

What is fermentation? How is it useful to us?

Answer:

Conversion of sugar, mollases and grape juice into alcohol and carbon dioxide is known as fermentation. It is usually carried out by yeast. This process is useful in the baking of bread, making of idli and dosa, and also in the making of wine.

Page No 30:

Question 20:

How is digestion in fungi different from digestion in human beings?

Answer:

Human beings digest their food inside their bodies, whereas fungi digest their food outside their bodies by releasing enzymes on the food. Once the food is digested it is absorbed by the fungi.



Page No 31:

Question 21:

List six uses of bacteria.

Answer:

Six uses of bacteria are as follows:
1) They help in nitrogen fixation.
2) They are used in the formation of antibiotics.
3) Spirulina is used as a protein-rich supplement.
4) They help in digestion in ruminants like cows.
5) They help in tanning of leather.
6) They are used in making vinegar.

Page No 31:

Question 22:

List four ways in which food can be preserved.

Answer:

Four ways in which food can be preserved are as follows:
1) Pasteurisation: In this method, milk is preserved by heating at 72°C for 15 seconds and then cooling it immediately.
2) Refrigeration: In this method, food items are preserved at 5°C.
3) Freezing: In this method, food items are preserved at -18°C.
4) Sun drying: In this method, food items like vegetables are dried under the Sun to remove the moisture content from them.

Page No 31:

Question 23:

List three conditions required for the growth of bacteria.

Answer:

Three conditions required for the growth of bacteria are as follows:
(a) Suitable temperature
(b) Moisture
(c) Enough food

Page No 31:

Question 24:

Explain the role of phytoplankton.

Answer:

Phytoplanktons are eaten by many aquatic animals, including some whales. They also play a major role in producing oxygen on the Earth.

Page No 31:

Question 25:

Why are viruses considered to be on the borderline between living and non-living things?

Answer:

Viruses do not grow and reproduce by themselves, which make them non-living. However, when a virus enters a living cell of an organism, it makes use of the resources in the host cell and starts reproducing. This makes viruses living as reproduction is an important characteristic of a living organism. Hence, viruses are considered to be on the borderline of living and non-living things.

Page No 31:

Question 26:

E. coli bacteria live in the intestines of human being and make vitamins for them. Can they be called parasites?

Answer:

No, E.coli bacteria cannot be called parasites because they do not harm humans beings. This kind of relationship, where both the partners get benefits from each other, is known as symbiotic relationship.

Page No 31:

Question 27:

Name the following:
(a) plant-like protist with a glass-like cell wall
(b) two viral diseases in human beings
(c) two diseases caused by bacteria in human beings
(d) thread-like structures that form the body of a fungus
(e) a whip-like structure used for movement
(f) two animal-like protists
(g) spherical bacteria
(h) asexual reproduction in bacteria
(i) organisms that live on other organisms and cause harm to them
(j) mode of asexual reproduction in yeast
(k) two diseases spread by droplet infection
(l) vectors for malaria and dengue
(m) one disease spread by direct contact
(n) two inoculations given in childhood

Answer:

(a) Diatoms

(b) Hepatitis and chicken pox

(c) Cholera, typhoid

(d) Hyphae

(e) Flagella

(f) Amoeba, Paramecium

(g) Coccus

(h) Binary fission

(i) Parasites

(j) Budding

(k) Chicken pox and tuberculosis

(l) Female Anopheles mosquito and female Aedes aegypti mosquito

(m) Conjunctivitis

(n) Polio and measles

Page No 31:

Question 28:

Give scientific reasons for the following:
(a) In colder parts of the world, summer vegetables are sun dried.
(b) Atta (wheat flour) can be stored for a longer duration than cooked chapattis.
(c) When yeast is kneaded with dough, dough rises after some time.
(d) Shoes and clothes get mould easily during the rainy season.

Answer:

(a) In colder parts of the world, summer vegetables are sun dried and preserved for the winters​ because it is not possible to grow fresh food in the winter season.

(b) Cooked chapattis contains moisture; therefore, they provide favourable conditions for the growth of microorganisms that spoil them. However, atta (wheat flour) can be stored for a longer duration as it does not have moisture in it.

(c) When yeast is kneaded with dough, the carbon dioxide released during the respiration of yeast causes fermentation and makes the dough to rise.

(d) Shoes and clothes get mould easily during the rainy season because mould grows best when there is warmth and enough moisture. 

Page No 31:

Question 29:

Study the classification chart carefully and fill in the blanks with the correct words.
Figure

Answer:

Rod shaped- Bacillus

Spherical shaped- Coccus

Spiral shaped- Vibrio

Found in flooded rice fields- Nostoc

Protein rich supplement- Spirulina

Cell wall is glassy, shell-like- Diatoms

Has flagella- Euglena

Moves with cilia- Paramecium

Moves with pseudopodia- Amoeba

Unicellular fungi- Yeast

Multicellular fungi- Mould

Unicellular algae- Clorella

Multicellular algae- Spirogyra



Page No 32:

Question 30:

Select the odd one out from the following sets. Give reasons for your answer.
(a) chickenpox, AIDS, hepatitis, cholera
(b) E. Coli, Nostoc, diatom, Spirulina
(c) Amoeba, Euglena, Paramecium, Plasmodium
(d) mould, Chlorella, yeast, Penicillium

Answer:

(a) Cholera
It is caused by bacteria, while the others are caused by viruses.

(b) Diatom
It is a protist, while the others are bacteria.

(c) Euglena
It contains chlorophyll, while the others do not.

(d) Chlorella
It is an algae, while the others are fungi.

Page No 32:

Question 31:

Atul ate fruits from a vendor. The fruits had been cut and exposed to flies and dust. What kind of diseases has he exposed himself to?

Answer:

Atul has exposed himself to diseases like typhoid, food poisoning, hepatitis, diarrhoea and dysentery. Cut fruits are exposed to flies that carry germs responsible for these diseases.

Page No 32:

Question 32:

What is meant by immunity? How can it be acquired artificially?

Answer:

Our body has a defence mechanism, which fights against infection by producing antibodies, thereby protecting our bodies from various disease-causing germs. This is known as immunity. 
It can be acquired by taking vaccines.



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