Question

Compare and contrast the plastids of Euglenids vs. green algae. What key features suggest a secondary endosymbiosis lead to the Euglenid plastid?

Answer 1

The similarities between euglenoids and green algae indicate that the chloroplasts of euglenoids originated in endosymbiotic green algae.

The chloroplasts of both euglenoids and green algae contain chlorophyll a and chlorophyll b. Euglenoids and green algae also have some carotenoid pigments in common, although euglenoids contain two pigments derived from carotenoids that are not found in either green algae or the higher plants.

While there are some similarities in pigmentation between euglenoids and green algae, the two groups have different food reserves. Green algae have food reserves of starch, while euglenoids have a carbohydrate food reserve called paramylon, which normally is present in the form of small, whitish bodies of varying shapes scattered throughout the cell.