Secondary succession occurs on

In a food chain,herbivores are:

What is the reason behind the deficit rising in a nutrient reservoir?

$A$ farmer harvests his crop and expresses his harvest in three different ways.
$(a)$ $I$ have harvested $10$ quintals of wheat.
$(b)$ $I$ have harvested $10$ quintals of wheat today in one acre of land.
$(c)$ $I$ have harvested $10$ quintals of wheat in one acre of land,$6$ months after sowing.
Do the above statements mean one and the same thing? If your answer is yes,give reasons. If your answer is 'no',explain the meaning of each expression.

The second trophic level in a pond ecosystem is ..........

Which of the following has the largest biomass of autotrophs in the world's oceans?