Role of endosymbiosis in spreading photosynthesis

Question 1

How did the very first chloroplast evolve?

Answer 1

endosymbiont theory

Process:
eukaryote engulfs cyanobacterium → becomes photosynthetic eukaryote → red algae, green algae, glaucophytes

Primary endosymbiosis gave way to secondary endosymbiosis, repeating the process again and again

By living as endosymbionts within eukaryote, cyanobacteria gave rise to chloroplasts, gradually evolving into them

Question 2

What was it before it became a chloroplast?

Answer 2

cyanobacterium

Question 3

What evidence do we have for this evolutionary process?

Answer 3

eukaryotic chloroplasts contain remnants of a peptidoglycan cell wall, which is only found in bacteria → cyanobacteria are a form of bacteria that can live as endosymbionts

Symbiodinium has stacks of thylakoid membranes, which are found within cyanobacteria → indicates an evolutionary connection between dinoflagellate Symbiodinium (a protist - eukarya) and cyanobacteria (bacteria) → connection between domains

Question 4

Where did the chloroplasts in dinoflagalletes come from, evolutionarily?

Answer 4

came from cyanobacteria

First stage: eukaryote engulfed cyanobacterium (primary endosymbiosis)

Second stage: over time, cyanobacteria membrane was lost

Third stage: evolution of red and green alga

Fourth stage: red alga engaged in secondary endosymbiosis, performing the process again

Fifth stage: secondary endosymbiosis led to dinoflagellates, apicomplexans, and stramenopiles evolving form red alga, which evolved from primary endosymbiosis