Page 13 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

(b) Parasitic Nutrition: In this type of nutrition, organisms (parasites) derive

nutrients from another living organisms (hosts), often harming them. For

example, cuscuta, mistletoe, etc.

(c) Symbiotic Nutrition: In this type of nutrition, two different types of

organisms live together and benefit from each other. For example, lichens is a

symbiotic relationship between algae and fungi, where algae provide food via

photosynthesis and fungi provide protection and minerals.
3. Discuss the significance of photosynthesis.

Ans. Significance of photosynthesis:

I. It is a primary source of energy for all organisms present on Earth.

II. It helps in purifying air and maintaining the balance of carbon dioxide and

oxygen in nature.

III. It helps in the synthesis of important nutrients present in food like carbohydrates,

fats and proteins.
IV. It leads to the origin of life on Earth by conversion of anaerobic conditions on

the planet to aerobic conditions that occurred millions of years ago and made

the planet habitable.

V. Fossil fuels found in nature have chemical energy stored in them which is the

solar energy that was trapped and stored during photosynthesis millions of

years ago.

4. Write the difference between autotrophs and heterotrophs.
Ans. Autotrophs Heterotrophs

1. These are organisms that can make These are organisms that cannot make
their own food with the help of their own food and depend on other

sunlight, carbon dioxide and water. for it.
2. They cannot move from one place to They can move from one place to

another in search of food. another in search for food.
3. They are also called producers as They are also called consumers as they
they can produce food. consume the food made by autotrophs.

4. They contain chlorophyll that helps They do not contain chlorophyll, hence
them in preparing their food. are dependent on producers for food.
5. For example, green plants, algae, For example, humans, animals, etc.

etc.

13