A student went to study a local pond. In one part of the pond she noticed tadpoles scraping at some pond weed. In another part she saw a water beetle holding a tadpole in its jaws.
(a) Construct a food chain for the pond.
(b) How many links are there in this chain ?

The surface of water in a lake appears green due to a layer of tiny free-floating organisms X on its surface. The lake water also contains organisms like water beetle, fish and tadpole. The sun shines over the lake water and provides energy for the functioning of this lake ecosystem. (a) What could organisms X be ? (b) Write a food chain comprising of all the four organisms metioned. (c) What is the general name of the food chains like the one written above ? (d) Name (i) secondary consumer (ii) producer (iii) tertiary consumer, and (iv) primary consumer, in the above food chain. (e) If the tertiary consumer gets 0.2 J of energy from the secondary consumer, then how much energy was radiated by the sun to the producer ?

(a) State one advantage of using jute bags over plastic bags for shopping. (b) Write a common food chain of a pond ecosystem having four links.

A water body characterized by nutrient rich water supports abundant growth of phytoplanktons and other water plants on its surface. Over time, the water body gets filled with a large number of such plants and the process is called Eutrophication. In such water bodies, dissolved oxygen content is nil or very less. A portion of a river is covered with a green layer of tiny floating organisms L on its surface and the pond water also contains organisms like tadpole, small fish, Alligator. Which of the following is the correct food chain for the above organisms?