NCERT Class VII Science Solutions: Chapter 1-Nutrition in plants Part 1

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Question 1:

Why do organisms need to take food?

Answer:

All organisms need to take food to get energy for the growth, development and maintenance of their bodies.

Question 2:

Distinguish between a parasite and a saprotroph.

Answer:

Difference between a parasite and a saprotroph:

Difference between Parasite and Saprotroph
Difference between parasite and saprotroph

Parasite

Saprotroph

Organisms derive nutrition from the body of other living organisms (host) are parasites.

Plants which derive nutrition from dead and decaying organisms are called saprophs.

Example: Cuscata (Amar bel)

Example: Mush

As showing in images is a All organisms need to take food to get energy for the growth

All Organisms Need to Take Food to Get Energy for the Growth

As showing in images is a All organisms need to take food to get energy for the growth

Cuscuta amarbel

Cuscuta Amarbel

Cuscuta amarbel

As showing in images is a result for Mushrooms.

Mushrooms.

As showing in images is a result for Mushrooms.

Question 3:

How would you test the presence of starch in leaves?

Answer:

  • Take a potted plant with variegated leaves – for example, money plant or crotons.

  • Keep the plant in a dark room for three days so that all the starch gets used up.

  • Image result for How would you test the presence of starch in leaves?

    Test of the Presence of Starch in Leaves

    Image result for How would you test the presence of starch in leaves?

  • Now select a leaf cover its portion with a black strip paper and keep the plant in sunlight for about six hours.

  • Pluck the leaf from the plant. Mark the uncovered area in it and trace them on a sheet of paper.

  • Dip the leaf in boiling water for a few minutes.

  • After this, immerse it in a beaker containing alcohol.

  • Carefully place the above beaker in a water-bath and heat till the alcohol begins to boil.

  • Now dip the leaf in a dilute solution of iodine for a few minutes.

  • Take out the leaf and rinse off the iodine solution.

  • You observe that the presence of starch in various areas of the leaf which was uncovered.