NCERT Solutions for Class 7 Science: Nutrition in Plants
Exercise Solutions
1. Why do organisms need to take food?
Organisms need to take food to obtain energy for performing various life processes such as growth, repair, and maintenance of the body, as well as to protect themselves from diseases and infections.
2. Distinguish between a parasite and a saprotroph?
- Parasite: An organism that lives on or inside another organism (host) and derives nutrients at the host’s expense. Example: Cuscuta (Dodder plant).
- Saprotroph: An organism that obtains nutrients from dead and decaying organic matter. Example: Fungi.
3. How would you test the presence of starch in leaves?
To test the presence of starch in leaves, perform the iodine test:
- Boil the leaf in water to kill it.
- Boil the leaf in alcohol to remove chlorophyll.
- Rinse the leaf in warm water to soften it.
- Add iodine solution to the leaf.
- The presence of starch will be indicated by a blue-black coloration.
4. Give a brief description of the process of synthesis of food in green plants?
Green plants synthesize food through photosynthesis. This process occurs in the chloroplasts, where chlorophyll captures solar energy and converts it into chemical energy. Carbon dioxide from the air and water from the soil are used to produce glucose and oxygen. The overall equation is:
6 CO2+6 H2O+ light energy→C6H12O6+ 6 O2
5. Show with the help of a sketch that the plants are the ultimate source of food.
Plants are the primary producers in the food chain. They convert solar energy into chemical energy through photosynthesis, producing food that other organisms (herbivores, carnivores, omnivores, and decomposers) depend on.
6. Fill in the blanks:
- (a) Green plants are called autotrophs since they synthesize their own food.
- (b) The food synthesized by the plants is stored as starch.
- (c) In photosynthesis, solar energy is captured by the pigment called chlorophyll.
- (d) During photosynthesis, plants take in carbon dioxide and release oxygen.
7. Name the following:
- (i) A parasitic plant with yellow, slender and tubular stem: Cuscuta
- (ii) A plant that has both autotrophic and heterotrophic mode of nutrition: Pitcher plant
- (iii) The pores through which leaves exchange gases: Stomata
8. Tick the correct answer:
- (a) Amarbel is an example of:
- (i) Autotroph
- (ii) Parasite ✔️
- (iii) Saprotroph
- (iv) Host
- (b) The plant which traps and feeds on insects is:
- (i) Cuscuta
- (ii) China rose
- (iii) Pitcher plant ✔️
- (iv) Rose
9. Match the items in Column I with those in Column II:
- Chlorophyll – Leaf
- Nitrogen – Bacteria
- Amarbel – Parasite
- Animals – Heterotrophs
- Insects – Pitcher plant
10. Mark ‘T’ if the statement is true and ‘F’ if it is false:
- (i) Carbon dioxide is released during photosynthesis. F
- (ii) Plants which synthesise their food themselves are called saprotrophs. F
- (iii) The product of photosynthesis is not a protein. T
- (iv) Solar energy is converted into chemical energy during photosynthesis. T
11. Choose the correct option from the following:
Which part of the plant takes in carbon dioxide from the air for photosynthesis?
- (i) Root hair
- (ii) Stomata ✔️
- (iii) Leaf veins
- (iv) Sepals
12. Choose the correct option from the following:
Plants take carbon dioxide from the atmosphere mainly through their:
- (i) Roots
- (ii) Stem
- (iii) Flower
- (iv) Leaves ✔️
13. Tick Mark (✔) the Correct Choice:
- (i) Which one of the following is an insectivorous plant?
- (a) Lichen
- (b) Venus fly trap ✔️
- (c) Mushrooms
- (d) Yeast
- (ii) Two different organisms living together and both benefiting from each other, are known as:
- (a) Saprophytic
- (b) Symbiotic ✔️
- (c) Parasitic
- (d) Heterotrophs
- (iii) Tiny pores on the surface of leaves are:
- (a) Lamina
- (b) Stomata ✔️
- (c) Chlorophyll
- (d) Leaf scale
- (iv) Which of the following is the green colour pigment in leaves:
- (a) Protoplast
- (b) Chloroplast
- (c) Chlorophyll ✔️
- (d) Anthocyanin
