1
Which of the following groups do not constitute a food chain?
(i) Wolf, rabbit, grass, lion
(ii) Plankton, man, grasshopper, fish
(iii) Hawk, grass, snake, grasshopper, frog
(iv) Grass, snake, wolf, tiger
[1 marks]
2
The percentage of solar energy which is not converted into food energy by the leaves of green plants in a terrestrial ecosystem is about:
[1 marks]
3
Assertion (A): The amount of ozone in the atmosphere began to drop sharply in the 1980s.
Reason (R): The oxygen atoms combine with molecular oxygen to form ozone.
[1 marks]
4
"Excessive use of chemicals and pesticides in agriculture adversely effect the environment." Justify this statement.
[2 marks]
5
Identify the food chain in which the organisms of the second trophic level are missing:
[1 marks]
6
Assertion (A): Accumulation of harmful chemicals is maximum in the organisms at the highest trophic level of a food chain.
Reason (R): Harmful chemicals are sprayed on the crops to protect them from diseases and pests.
[1 marks]
7
(A)
Plants $\rightarrow$ Deer $\rightarrow$ Lion
In the given food chain, what will be the impact of removing all the organisms of second trophic level on the first and third trophic level? Will the impact be the same for the organisms of the third trophic level in the above food chain if they were present in a food web? Justify.
OR
(B)
A gas 'X' which is a deadly poison is found at the higher levels of atmosphere and performs an essential function. Name the gas and write the function performed by this gas in the atmosphere. Which chemical is linked to the decrease in the level of this gas? What measures have been taken by an international organization to check the depletion of the layer containing this gas?
[3 marks]
8
How do harmful chemicals get accumulated progressively at each trophic level in a food chain?
[2 marks]
9
(a) (i) Why does a kitchen garden called an artificial ecosystem while a forest is considered to be a natural ecosystem?
(ii) While designing an artificial ecosystem at home, write any two things to be kept in mind to convert it into a self-sustaining system. Give reason to justify your answer.
OR
(b) (i) Construct a food chain of four trophic levels comprising the following: Hawk, snake, plants, rat.
(ii) 20,000 J of energy was transferred by the producers to the organism of second trophic level. Calculate the amount of energy that will be transferred by organisms of the third trophic level to the organisms of the fourth trophic level.
[3 marks]
10
(a)
What is ozone? How is it formed in the upper layers of the Earth's atmosphere? How does ozone affect our ecosystem?
OR
(b)
(i)
List two human-made ecosystems.
(ii)
"We do not clean a pond in the same manner as we do in an aquarium." Give reason to justify this statement.
[2 marks]
11
(a) Name the group of organisms which form in the first trophic level of all food chains. Why are they called so?
(b) Why are the human beings most adversely affected by bio-magnification?
(c) State one ill-effect of the absence of decomposers from a natural ecosystem.
[3 marks]