Some of the nutrient cycles are labelled as below:
$I$. Sulphur cycle
$II$. Phosphorus cycle
$III$. Carbon cycle
$IV$. Nitrogen cycle
Of these,the sedimentary cycle is represented by:

Fill in the blanks.
$(a)$ Plants are called as . . . . . . because they fix carbon dioxide.
$(b)$ In an ecosystem dominated by trees,the pyramid (of numbers) is . . . . . . type.
$(c)$ In aquatic ecosystems,the limiting factor for the productivity is . . . . . . .
$(d)$ Common detritivores in our ecosystem are . . . . . . .
$(e)$ The major reservoir of carbon on earth is . . . . . . .

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:

The first link in any food chain is a green plant because

Which of the following biochemical cycles has a gaseous phase?

What is the approximate amount of carbon fixed in the biosphere annually through photosynthesis?