How are primary and secondary succession similar and how are they different?

They are similar in that both involve the growth of new organisms in an environment. However they differ in that primary succession occurs in a place where no life had been before, while secondary succession occurs in place where life had been before, but was destroyed.

Some examples of primary succession include the formation of a new ecosystem after a volcano, glacier outbursts, or a nuclear explosion. Some examples of secondary succession include succession after fire, harvesting, logging, or abandonment of land or the renewal after a disease outbreak.

In primary succession, newly exposed or newly formed rock is colonized by living things for the first time. In secondary succession, an area that was previously occupied by living things is disturbed, then re-colonized following the disturbance.