Cyanobacteria (blue-green algae) were first photosyntheiic organisms. They contain photosynthetic lamellae equivalent to thylakoids, hence these are autotrophic. Green algae (Chlorophyceae) are autotrophs like higher plants, they evolved later. They contain chlorophyll-a and b. Red algae (Rhodophyceae) are generally marine plants. They contain chlorophyll-a and d.