Phycology (or Algology) is the study of algae. Most algae are eukaryotic, photosynthetic organisms that live in a wet environments. They are distinguished from the higher plants by a lack of true roots and leavess. Many species are single-celled and microscopic; many others are multicellular to one degree or another, some of these growing to large size (for example, seaweeds such as kelp). Algae are important as primary producers in aquatic ecosystems.