In a grassland ecosystem, match the trophic levels with their correct example species:

$(a)$ 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:

What happens if green plants are removed from an aquarium?

Which of the following statements are correct regarding a food chain?
$(a)$ If $80\%$ of tigers are removed from an area,the growth of vegetation in that area increases.
$(b)$ If carnivores are removed from an area,the population growth of deer increases.
$(c)$ The length of a food chain is limited to $3$ to $4$ trophic levels because the amount of energy decreases in the ecosystem.
$(d)$ The length of a food chain is usually $2$ to $8$ trophic levels.

Which one of the following is not a gaseous biogeochemical cycle in ecosystem?

Ecological succession on sand is known as:

Match the following columns correctly:

Column-$I$	Column-$II$
$(i)$ Producers	$(P)$ Primary consumers
$(ii)$ Herbivores	$(Q)$ Net primary productivity
$(iii)$ Carnivores	$(R)$ Primary trophic level
$(iv)$ Top carnivores	$(S)$ Secondary productivity