An ecosystem can be visualised as a functional unit in nature, where living organisms interact among themselves and with the surrounding physical environment also. The interaction of the biotic and abiotic components results in a physical structure that is characteristic of an ecosystem.
(a) Name the two features that define the structural aspect of an ecosystem.
(b) Mention the four common functional aspects of an ecosystem.

Organisms occupy a specific place in their natural surroundings or in a community according to their feeding relationship with the other organisms. Based on the source of nutrition of food organisms occupy a particular place, called trophic level, in a food chain.
(a) What technical term is given to the organisms occupying the first, second and third trophic levels in a food chain?
(b) Choose an example for each of the above trophic levels, from the following list of organisms: Rabbit, Wolf, phytoplanktons, frog, snail, Hydrilla, jackal.

A part of an aquatic ecosystem is represented in the picture provided above.
(a) Mention the relationship between  and  with respect to population interaction

(c) Construct a food chain operating in this ecosystem.

Pyramids of Biomass of two types are shown in the diagram given above.
Answer the following questions.
(a) Identify the type of ecosystems in which the pyramid of biomass A and B occur, respectively.
(b) Why is the pyramid A inverted and B upright?

Over the years, it has been observed that some of the lakes are disappearing due to urbanisation. In the absence of human interference, depict through a flow chart, how the successional series progresses from hydric to mesic condition.