English Medium इयत्ता १० - CBSE Important Questions for Science

Your mother always thought that fruit juices are very healthy for everyone. One day she read in the newspaper that some brands of fruit juices in the market have been found to contain certain level of pesticides in them. She got worried as pesticides are injurious to our health.
(a) How would you explain to your mother about fruit juices getting contaminated with pesticides?
(b) It is said that when these harmful pesticides enter our body as well as in the bodies of other organisms they get accumulated and beyond a limit cause harm and damage to our organs. Name the phenomenon and write about it.

"Energy flow in food chains is always unidirectional". Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.

What are decomposers? What will be the consequence if the decomposers are completely eradicated from an ecosystem? Give justification in support of your answer.

DDT was sprayed in a lake to regulate breeding of mosquitoes. How would it affect the trophic levels in the following food chain associated with a lake? Justify your answer.

In the following food chain, vertical arrows indicate the energy lost to the environment and horizontal arrows indicate energy transferred to the next trophic level. Which one of the three vertical arrows (A, C and E) and which one of the two horizontal arrows (B and D) will represent more energy transfer? Give reason for your answer.

A food chain in a forest ecosystem

Draw a diagram showing flow of energy from solar input to a food chain having four trophic levels in an ecosystem. List two inference that can be drawn from the energy flow diagram.

Study the picture given below showing three food chains (a), (b) and (c) and answer the following questions:

1. Name the type of ecosystems that exist in food chains (b) and (c).
2. The first trophic level in all food chains is producers. Why? What percentage of solar energy do these producers capture for their use?
3. Why are the arrows shown in the diagram in one direction only and not vice versa? Justify.