Question

What is the theory of secondary endosymbiosis?

Answer 1

Secondary endosymbiosis occurs when the product of primary endosymbiosis is itself engulfed and retained by another free living eukaryote.

Explanation:

Secondary endosymbiosis has occurred several times and has given rise to extremely diverse groups of algae and other eukaryotes. Some organism take opurtunistic advantage --- they engulf the alga and use the products of its photosynthesis. Once the prey dies or is lost, the host returns to a free living state.

The heterotrophic protist Hatena behaves like a predator until it ingests a green alga. The alga loses its flagella and cytoskeleton and Hatena ( now host ) switches to photosynthetic nutrition. It gains ability to move towards light and lose its own feeding mechanism.