What is true about the phosphorus cycle?
$I.$ Rocks are the natural reservoirs of phosphorus.
$II.$ Weathering of sedimentary rocks makes phosphate available to the soil.
$III.$ Herbivores and carnivores obtain phosphorus from plants directly or indirectly.
Choose the correct option.

What type of food chain is the following?
Grass $\rightarrow$ Goat $\rightarrow$ Human

Consider the following statements concerning food chains.
$A.$ Removal of $80\%$ tigers from an area resulted in greatly increased growth of vegetation.
$B.$ Removal of most of the carnivores resulted in an increased population of deers.
$C.$ The length of food chains is generally limited to $3-4$ trophic levels due to energy loss.
$D.$ The length of food chains may vary from $2$ to $8$ trophic levels.
Which two of the above statements are correct?

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:

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?

$A$ person who eats vegetables acts as a: