The number of organisms present at any trophic level in an ecosystem depends on which of the following factors?

In a lake,phytoplankton grow abundantly in

The vertical distribution of different species occupying different levels is called $..........$.

Choose the incorrect option for the cost distribution of ecosystem services.

In a food chain,herbivores are:

$A$ 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.