$A$ community which starts succession in a habitat is

Vertical distribution of different species occupying different levels in a biotic community is known as

$A$ 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.

Phosphorus usually becomes a limiting factor at certain times of the year in which ecosystem?

Identify the correct sequence of succession in a hydrarch (aquatic) habitat.

What do all the ecosystems of nature collectively form?