Answer in 40 to 80 words:
What is ecological succession? Distinguish primary succession from secondary succession.

Ecological succession is the directional change in the flora and fauna of a given region over a period of time. It is of two types primary and secondary.

1) Primary succession is the sequence of changes that happens in an entirely new habitat which has never been colonized before. For example- newly formed sand dunes.

2) Secondary succession is the sequence of changes that happens on a previously colonized but damaged habitat. For example- plants are grown in an area after land clearance or a fire.