Our Environment

HOTS Questions for Class 10 Science Chapter 15 Our Environment

Question 1.
Study the figure. What does it depict ?

Answer:
It is representation of movement of energy and matter in the biosphere.
Energy flow is unidirectional while matter is repeatedly recycled.

Question 2.
Which trophic level eats nothing and which one is not eaten.
Answer:
Eats Nothing: Producers.
Not Eaten: Top carnivores.

Question 3.
What is the reason that a food chain consists of only 3-5 steps ?
Answer:
As per 10% law of Lindeman (1942), the energy available decreases by 90% with the rise of trophic level. 2000 J of energy available at the producer or T₁ level will provide only 2 J of energy to second order carnivores (T₄).
Therefore, an ecosystem cannot have food chains of several steps.

Question 4.
Describe how decomposers facilitate recycling of matter in order to maintain balance in the ecosystem.
Answer:
Decomposers act on organic or biodegradable wastes by secreting digestive enzymes over them. Organic waste is broken down into soluble simpler substances. Decomposers pick up the simple organic substances for their own use leaving the inorganic substances. The phenomenon is called mineralisation. Minerals released from decaying organic matter become available to plants for reuse. Decomposers, therefore, help in recycling of minerals and maintain the balance in the ecosystem.