An ecosystem,such as an aquarium,is self-sustaining if it involves the interaction between organisms,a flow of energy,and the presence of

Define the following terms:
$(i)$ Saprotrophs
$(ii)$ Trophic level

In a lake,phytoplankton grow abundantly in

Choose the incorrect option with respect to the amount of living material present in different trophic levels at a given time.

In a pond ecosystem,benthos means

Consider the following statements about the carbon cycle and choose how many statements are correct?
$(a)$ The atmosphere contains $71\;\%$ of the total global carbon.
$(b)$ Decomposers contribute substantially to the $CO_2$ pool by processing waste materials and dead organic matter from land or oceans.
$(c)$ $4 \times 10^{13}\; kg$ of carbon is fixed through photosynthesis annually.
$(d)$ There is no respiratory input into the atmosphere.
$(e)$ Carbon constitutes $49\;\%$ of the dry weight of organisms.