Compare primary and secondary succession of an ecosystem. what is the distinction between them?

Primary succession is the establishment of a community in an area with no soil, while secondary succession is the establishment of a new community in an existing ecosystem that was disturbed by some catastrophic event.

An autotrophic protist - they can perform photosynthesis and mainly consist of unicellular algae. they can be divided into number of systematic group according to the shape of their cell and the type of photosynthetic pigments they use.