Generally,the food chain has how many trophic levels?

Which of the following is $NOT$ a gaseous biogeochemical cycle in an ecosystem?

Match the trophic levels with their correct species examples in a grassland ecosystem.

$(a)$ Fourth trophic level	$(i)$ Crow
$(b)$ Second trophic level	$(ii)$ Vulture
$(c)$ First trophic level	$(iii)$ Rabbit
$(d)$ Third trophic level	$(iv)$ Grass

Select the correct option:

In the dry weight of living beings,$A$ $\%$ carbon is present. In the oceans,$B$ $\%$ of the total global carbon is dissolved. The total amount of carbon in the atmosphere is $C$ $\%$ of the total global carbon. Identify the correct values for $A, B,$ and $C$.

Identify the possible link '$M$' in the following food chain.
Plant $\rightarrow$ Insect $\rightarrow$ $M$ $\rightarrow$ Snake $\rightarrow$ Eagle

Match the following columns:

Column-$I$	Column-$II$
$P$. Herbivores	$I$. Directly dependent on plants
$Q$. Carnivores	$II$. Indirectly dependent on plants
$R$. Saprophytes (Fungi)	$III$. Dependent on dead or decaying matter