The mass of living material at a trophic level at a particular time is called

Consider the following statements concerning food chains.

$I$. Removal of $80\; \%$ tigers from an area resulted in greatly increased growth of vegetation.

$II.$ Removal of most of the carnivores resulted in an increased population of deers.

$III.$ The length of food chains is generally limited to $3$ to $4$ trophic levels due to energy loss.

$IV.$ The length of food chains may vary from $2$ to $8$ trophic levels.

Which two of the above statements are correct?

The zooplanktonic forms are

Which is not a structural aspect of ecosystem?

Which one of the following components of ecosystem comes from outside