CBSE Class 7 Science Advanced Biology Nutrition in Plants and Animals Long Answer Questions Set 01

Long Answer Questions

Question 1. What is heterotrophic nutrition? Explain its different types.
Answer:
Heterotrophic nutrition is the mode of nutrition in which an organism depends on another organism for its food. All animals and non-green plants are heterotrophic. Its types are:
1. Holozoic nutrition: intake of solid or liquid food, its digestion, absorption, use of the energy and egestion of the waste. Example: human beings.
2. Parasitic nutrition: the parasite gets food from a living organism called the host. The host does not benefit and may even be harmed. Example: head lice.
3. Saprophytic nutrition: the organism feeds on dead and decaying plants and animals. Such organisms are saprophytes. Example: fungus.
In simple words: Heterotrophs cannot make food, so they depend on others in three ways.

Teacher's Note:
1. Define first, then explain each type with an example.
2. Use headings to score full marks.

Question 2. What is photosynthesis and why is it important?
Answer:
Photosynthesis is the process by which green plants make their own food from carbon dioxide and water, using sunlight energy and chlorophyll. It occurs in the leaves.
\( 6CO_2 + 6H_2O \xrightarrow{\text{sunlight, chlorophyll}} C_6H_{12}O_6 + 6O_2 \)
Importance: green plants are the producers of an ecosystem. The food and energy they make is used directly or indirectly by all other organisms. Photosynthesis also releases oxygen into the air.
In simple words: Photosynthesis is the food-making process of green plants, and everyone depends on it.

Teacher's Note:
1. Write the balanced equation.
2. Mention producers and oxygen in the importance.

Question 3. Explain classification of animals based on the nutrition type.
Answer:
Animals with holozoic nutrition are grouped on the basis of what they eat:
1. Herbivores: depend directly on plants such as grass and leaves, and have teeth and a digestive system suited to plant material. Examples: cow, goat.
2. Carnivores: flesh eaters that feed on other animals. They have sharp teeth and a digestive system for flesh and are also called predators; the animals they eat are prey. Example: tiger.
3. Omnivores: eat both plants and animals and have teeth and a digestive system for both. Examples: bear, human.
In simple words: Animals are herbivores, carnivores or omnivores according to their food.

Teacher's Note:
1. Link food, teeth and digestive system for each group.
2. Give two examples if you can.

Question 4. Compare the nutrition type in green plants and Cuscuta.
Answer:
Green plants have autotrophic nutrition: they contain chlorophyll and make their own food by photosynthesis, using carbon dioxide, water and sunlight.
Cuscuta is a parasitic plant with heterotrophic (parasitic) nutrition: it gets some or all of its food from another living plant.
In simple words: Green plants make their food, Cuscuta takes it from another plant.

Teacher's Note:
1. Use the words autotrophic and parasitic.
2. Present the answer as two short points.

Question 5. What is the difference between mode of nutrition in head lice and venus flytrap?
Answer:
Head lice are parasites that live on the hair of human beings and take food from the living host. The host gets no benefit and may be harmed.
The Venus flytrap is an insectivorous plant. It gets some or most of its nutrients, especially nitrogen, by trapping and consuming small insects.
In simple words: Lice feed on a living host, the flytrap catches and digests insects.

Teacher's Note:
1. One is an animal parasite, the other is a plant.
2. Remember nitrogen for the flytrap.

Question 6. Write the different steps involved in nutrition.
Answer:
The five steps of nutrition are:
1. Ingestion: intake of food; it varies from animal to animal.
2. Digestion: breaking down complex food into simpler substances.
3. Absorption: taking the digested food into the body (blood).
4. Assimilation: using the absorbed food for various body activities.
5. Egestion: removal of waste material from the body.
In simple words: Take in, break down, absorb, use and throw out the waste.

Teacher's Note:
1. Learn the order with the first letters I, D, A, A, E.
2. Define each step in one line.

Question 7. What are the different parts of human body involved in human digestion and mention their function?
Answer:
Mouth: ingestion, with some mechanical and chemical digestion.
Oesophagus: a long muscular tube through which food reaches the stomach.
Stomach: mechanical and chemical digestion.
Small intestine: chemical digestion and absorption.
Large intestine: reabsorption of water.
Rectum and anus: egestion (the rectum stores waste and the anus lets it out).
In simple words: Each part of the food canal does one job, from the mouth to the anus.

Teacher's Note:
1. Go in the order the food travels.
2. Add a labelled diagram if time permits.