Class Notes NCERT Solutions for CBSE Students
Question: Write a short note on the cycle of nutrients.
Answer: A food chain is formed when one organism eats another organism for food. For example- grasshoppers depend on grass and plants for food. Frog eats the grasshoppers. Snakes eat the frogs for their food. This dependence of organisms on one another for food forms a food chain.
Here, grass produces its own food. It is a producer. The grasshopper depends directly on grass, so it is known as primary consumer. The frog then feeds on the grasshopper. It is indirectly dependent on the producers and is called secondary consumer. Forests are home to many such food chains.
There is another group of animals that depends on both plants and animals for their food. They are called omnivores. For example- bear, wild boar, wild dogs etc. When animals die their bodies are eaten by crows, vultures and hyenas. This group of animals is called scavengers. The bodies of dead plants and animals get broken down into simple substances or are decomposed by decomposers like fungi and bacteria present in the soil. The fertility of the soil increased by these decomposers.
The energy from the plants enters the consumers in the form of food. This eventually ends up at the decomposers and is released into the soil. This again used by the plants forming a cycle known as the cycle of nutrients.
Question: Discuss the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere.
Answer: The forest plays an important role in maintaining the balance between oxygen and carbon dioxide in the atmosphere. As we know plants for their food nutrition requirement make use of process of photosynthesis, in which they consume Carbon Dioxide, released by the living organism from the environment. As a result of photosynthesis, plants release oxygen which is again consumed by living beings for respiration and this cycle goes on.
Question: There is no waste in a forest. Explain.
Answer: There are several organisms and micro-organisms that live in the soil convert waste into useful nutrients called humus. This is why there is no waste in forest.
Question: Explain how animals dwelling in the forest help it grow and regenerate.
Answer: The wide variety of animals helps the forest to regenerate and grow. In forest, plants produce food. All animals, whether herbivores or carnivores, depend ultimately on plants for food. Organisms which feed on plants often get eaten by other organisms, and so on. For example, grass is eaten by insects, which in turn, is taken by the frog. The frog is consumed by snakes. This is said to form a food chain:
Grass→ insects→ frog→ snake→ eagle
Many food chains can be found in the forest. All food chains are linked. If anyone food chain is disturbed, it affects other food chains. These food chains produce a lot of supplementary products which are vital for the plants growth. The micro-organisms which convert the dead plants and animals to humus are known as decomposers. Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Decaying heap of animal dropping is good source of nutrition for plants in the forest. The decaying animal dung also provides nutrients to the seedlings to grow. The animals also disperse the seeds of certain plants and help the forest to grow.
