The economic importance of algae given in plant kingdom class 11 ncert are:

1. Green algae such as Ulva, Caulerpa, Enteromorpha, Chlorella, etc are used as food rich in lipid, protein, vitamins, minerals etc.

2. Chlorella and Caulerpa are used to obtain antibiotics also.

3. A number of green algae such as Chlamydomonas, Chlorella, Scenedesmus, etc are used in sewage oxidation tanks.