algae

Highly varied group of plants, ranging from single-celled forms to large and complex seaweeds. They live in both fresh and salt water, and in damp soil. Algae do not have true roots, stems, or leaves.

Marine algae help combat global warming by removing carbon dioxide from the atmosphere during photosynthesis.

Because of their diversity, botanists have established seven separate algae groupings or divisions, belonging to three different kingdoms: Cyanobacteria (blue-green algae) of the kingdom Monerans; Chrysophyta (golden algae diatoms), Englenophyta (plidosynthetic flagellates) and Pyrrophyta (dinoflagellates) of the kingdom Protists; and Rhodophyta (red algae), Phaeophyta (brown algae), and Chlorophyta (green algae) of the kingdom Plants.

The life cycles of algae vary widely; some reproduce solely by vegetative means, others have a prolonged haploid phase, and a very restricted diploid phase. However, some advanced algae have their haploid generation reduced almost as much as it is in seed plants.