Question

Describe the origin of plastids and the evolutionary relationships among red algae, green algae, and plants.

Answer 1

Plastids are membrane bound organelles generally found in the cells of plants, algae, and some eukaryotic organisms. They contain some colored pigments like chloroplast and rhodoplasts. They are the sites for synthesis and storage. They are believed to be originated by endosymbiosis of cynobacteria, a phylum of bacteria which can synthesize their own food by photosynthesis.

This primary endosymbiosis event gave rise to three autotrophic clades with primary plastids: the green plants, the red algae and the glaucophytes. Green algae are often classified with their embryophyte descendants in the green plant clade Viridiplantae . Viridiplantae, together with red algae and glaucophyte algae, form the supergroup Primoplantae.