Which group of living organisms given below is a link in the food chain between green plants and a hawk?

Which of the following organisms convert plant matter into animal matter?

Consider the following statements about food chain:
$I.$ The transfer of energy from producers to top consumers through a series of organisms is called a food chain.
$II.$ $A$ food chain is always straight and proceeds in a progressive straight line.
$III.$ In a food chain,there is a unidirectional flow of energy from the sun to producers and subsequently to a series of different types of consumers.
Which of the statements given above are correct?

Which one of the following statements is incorrect for secondary succession?

The primary succession in a sere is

If plants (producers) of an ecosystem die,then the system