How do I know that the algae is endo-energetic? what do it depend on?

Question

How do I know that the algae is endo-energetic? what do it depend on?

Answer 1

I'm pretty sure endoenergetic is not the right word.  I think you mean "Autotrophic", which means it produces it's own food, like a plant, rather than taking it from other organisms, like an animal, which is called  "Heterotrophic".

The vast majority of algae are autotrophic.  They take in sunlight and use it to produce sugars, which gives them energy.  Some of them are green, like plants, some of them are amber/brown, and some of them are even red.  There are a few other varieties (blue-green and golden), but they are special in various ways.

There are some heterotrophic algae, which are parasites, like Plocamiocolax, which is a small pale warty growth on Plocamium, a branching red algae.  Most parasitic algae that I've encountered are about like that, actually.

Answer 2

Endo-energetic reactions are photochemical reactions and are the direct outcome of photogalvanic conversion that occurs in chloroplasts that do not contain thylakoids membranes and grana stacks.  You are able to tell that this because algae has very simple (evolutionarily) chloroplasts.