NCERT Class 7 Science Model Paper 2 Questions and Answers Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Section – C: Biology

23. Which of the following is/are the important agent of soil erosion?

(1) Water

(2) Wind

(3) Trees

(4) Both (1) and (2)

Ans: Option (4)

Both water and wind are important agents of soil erosion.

24. Which of the following structure help in gaseous exchange in the organism shown in the diagram?

Gaseous Exchange in the Organism

(1) Gills

(2) Trachea

(3) Lungs

(4) Skin

Ans: Option (4)

The organism shown in the given diagram is earthworm and the structure which help in gaseous exchange in earthworm is skin.

25. Upward movement of water and minerals occurs through pipe-like structure called

(1) Phloem

(2) Xylem

(3) Stomata

(4) All of these

Ans: Option (2)

Upward movement of water and minerals occurs through pipe-like structure called xylem.

26. Which of the following statement is incorrect?

(1) Forests control noise pollution.

(2) Forests provide home and protection to wildlife.

(3) Forests increase the intensity of floods.

(4) Forests regulate the balance of and .

Ans: Option (3)

Forest decreases the intensity of floods.

27. Statement-I: Vegetative propagation is an asexual method of reproduction in plants where vegetative parts namely the root, stem, leaf or buds give rise to new plants.

Statement-II: Plants produced by this method are identical copies of the parent plant and show no variations.

(1) Both statements I and II are true and the statement II is the correct explanation of statement I.

(2) Both statements I and II are true but statement II is not the correct explanation of statement I.

(3) Statement I is true, but statement II is false.

(4) Both statement I and II are false.

Ans: Option (2)

Both statements I and II are true but statement II is not the correct explanation of statement I.

28. Which type of soil has (i) Highest percolation rate (ii) Lowest percolation rate

Ans: (i) Highest percolation rate: Sandy soil

(ii) Lowest percolation rate: Clayey soil

29. What is the function of red blood cells?

Ans: Red blood cells carries oxygen from lungs to the cells of the body (Transportation of oxygen) .

30. Write the main nitrogenous waste excreted by (i) Human (ii) Fish

Ans: (i) Human: In human main nitrogenous waste is urea.

(ii) Fish: In fish main nitrogenous waste is ammonia.

31. (i) Which type of reproduction take place in Spirogyra?

(ii) What do you mean by embryo?

(iii) Write difference between unisexual and bisexual organism.

Ans:

(i) Fragmentation is a type of reproduction take place in spirogyra.

(ii) A ball-like structure formed after divisions in the fertilized egg (zygote) .

(iii) Unisexual organism: When male and female reproductive parts are present in separate individuals, they are known as unisexual organisms.

Bisexual organism: When male and female reproductive parts are present within the same individual, they are known as bisexual organisms.

32. (i) How are plants dependent on animals?

(ii) Write the importance of scavengers and decomposers in nature.

Ans: (i) Plants depends on animals

  • For Carbon dioxide: Plants need carbon dioxide to prepare food through photosynthesis. This carbon dioxide comes from animals during respiration.
  • For Pollination: In some plants, pollination is brought about by insects, birds and bats. Without pollination, formation of seeds in these plants would not be possible.
  • For Seed dispersal: Seed dispersal in many plants is through animals and even man. Fruits are eaten by animals such as the birds who carry them to distant places. Finally, the seeds are passed out in their excreta without any damage.

(ii) Scavenger and decomposers are important for nature. Scavengers (vultures or crows) eating dead animals and decomposers (bacteria and fungi) breakdown the organic matter of dead organisms into simple nutrients in the soil.

Scavenger and decomposers help in cleaning the nature or environment.

33. (i) What is transpiration?

(ii) Give any two functions of transpiration.

Ans: (i) Transpiration

Transpiration is the process of loss of water in a vapour form from the leaves in plants.

It occurs through stomata present in the leaves by the process of diffusion.

(ii) Functions of transpiration

(a) It results in the transport of water and minerals from the soil to the leaves. In the leaves, water forms the raw material for photosynthesis.

(b) It produces a cooling effect which helps in preventing hot sunlight from damaging delicate cells.

34. (i) Write the equation of

(a) Aerobic respiration

(b) Anaerobic respiration in both yeast and muscle cells

(ii) Write difference between inhalation and exhalation.

Ans: (i) (a)

(b) In yeast

In muscle cells

(ii) Inhalation: Ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs. The lungs get filled with air.

Exhalation: Ribs move down and inwards, while diaphragm moves up to its former position.

This reduces the size of the chest cavity and air is pushed out of the lungs. These movements in our body can be felt easily.

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