Trees $\rightarrow$ Birds $\rightarrow$ Lice $\rightarrow$ Bacteria. Thus,the food chain is:

What will happen to an ecosystem if:
$(a)$ All producers are removed;
$(b)$ All organisms of herbivore level are eliminated; and
$(c)$ All top carnivore population is removed?

Identify the mismatched pair.

Biological equilibrium is found among the

Maximum contribution of $O_2$ is from

Maximum absorption of rainfall water is done by