What is the basis of the classification of algae?

Basis of classification:

1. It is a group of principally photosynthetic, aquatic, and nucleus-comprising species, which are devoid of true stems, roots, leaves, and unique multicellular reproductive compositions of plants.
2. The absence or presence of pigments is the prime basis for algae classification.
3. In blue-green algae or Chlorophyceae, the existence of chlorophyll a and b give green colour to it.
4. In brown algae or Phaeophyceae, fucoxanthin and chlorophyll a and c are found. The fucoxanthin provides the brown colour.
5. In red algae or Rhodophyceae, phycoerythrin and chlorophyll a and d are found. The phycoerythrin gives red colour.