CBSE – 7th Standard Science

Question Bank – Chapter 1 – Nutrients in Plants



Qus 1.
Name some components of food?

Ans. Carbohydrates, proteins, fats, vitamins and minerals are components of food. Components of food which are necessary for our body are called nutrients.

Qus 2.
Why humans and animals are directly or indirectly dependent on plants?

Ans. All living organisms require food. Plants can make their food themselves but animals including humans cannot. They get it from plants or animals that
eat plants. Thus, humans and animals are directly or indirectly dependent on plants.

Qus 3. How plants prepare their own food

Ans. Plants are the only organisms that can prepare food for themselves by using water, carbon dioxide and minerals. The raw materials are present in their
surroundings. The nutrients enable living organisms to build their bodies, to grow, to repair damaged parts of their bodies and provide the energy to carry
out life processes.

Qus 4. Explain the term Autotrophic and Heterotrophs?

Ans. Nutrition is the mode of taking food by an organism and its utilization by the body. The mode of nutrition in which organisms make food themselves
from simple substances is called autotrophic (auto = self; trophos = nourishment) nutrition. Therefore, plants are called autotrophs whereas Animals and
most other organisms take in readymade food prepared by the plants. They are called heterotrophs (heteros = other).

Qus 5. Explain the food making process of plants?

Ans. Leaves are the food factories of plants. The synthesis of food in plants occurs in leaves. Therefore, all the raw materials must reach there. Water
and minerals present in the soil are absorbed by the roots and transported to the leaves.

Qus 6. What is Cell membrane?

Ans. You have seen that buildings are made of bricks. Similarly, the bodies of living organisms are made of tiny units called cells. Cells can be seen only
under the microscope. Some organisms

are made of only one cell. The cell is enclosed by a thin outer boundary, called the cell membrane

Qus 7. What is Cytoplasm?

Aans. Most cells have a distinct, centrally located spherical structure called the nucleus. The nucleus is surrounded by a jelly-like substance called

Qus 8. What is Stomata?

Ans. Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. These pores are surrounded by ‘guard cells’. Such
pores are called stomata.

Qus 9. How water and minerals are absorbed by roots reach the leaves?

Ans. Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, the stem, the branches and the leaves. They
form a continuous path or passage for the nutrients to reach the leaf.

Qus 10. What is Photosynthesis?

Ans. The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This energy is used to synthesise (prepare)
food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis.

Qus 11. Why Sun is the ultimate source of energy for all living organisms?

Ans. Chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of photosynthesis. It is a unique process on the earth. The
solar energy is captured by the leaves and stored in the plant in the form of food. Thus, sun is the ultimate source of energy for all living organisms.

Qus 12. What are the other places in plants where photosynthesis takes place?

Ans. Besides leaves, photosynthesis also takes place in other green parts of the plant in green stems and green branches. The desert plants have scale- or
spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.

Qus 13. What is an Algae?

Ans. We often see slimy, green patches in ponds or in other stagnant water bodies. These are generally formed by the growth of organisms called algae.
Algae are green in colour, they contain chlorophyll which gives them the green colour. Algae can also prepare their own food by photosynthesis.

Qus 14. What is Heterotrophic mode of nutrition?

Ans. There are some plants which do not have chlorophyll, they cannot synthesise their food. So for their survival on earth like humans and animals such
plants depend on the food produced by other plants. They use the heterotrophic mode of nutrition.

Qus 15. What are insectivorous plants?

Ans. When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair. The insect is digested by the digestive
juices secreted in the pitcher. Such insect-eating plants are called insectivorous plants.

Qus 16. What is saprotrophic nutrition?

Ans. Fungi secrete digestive juices on the dead and decaying matter and convert it into a solution, then they absorb the nutrients from it. This mode of
nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition.

Qus 17. What is symbiotic relationship? Explain with example

Ans. Some organisms live together and share shelter and nutrients. This is called symbiotic relationship. For example, certain fungi live in the roots of
trees. The tree provides nutrients to the fungus and, in return, receives help from it to take up water and nutrients from the soil.

Qus 18. Explain the food making process of lichens?

Ans. In organisms called lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together. The fungus provides shelter, water and
minerals to the alga and, in return, the alga provides food which it prepares by photosynthesis.

Qus 19. How nutrients are replenished in the soil?

Ans. Plants absorb mineral nutrients from the soil. So, their amounts in the soil keep on declining. Fertilizers and manures contain plant nutrients such
as nitrogen, potassium, phosphorous, etc. These nutrients need to be added from time to time to enrich the soil. We can grow plants and keep them healthy
if we can fulfill the nutrient requirement of plants.