Algae are the simplest kinds of plants. They contain chlorophyll; therefore, they can make their food by photosynthesis. They lack vascular bundles, i.e. they do not posses xylem and phloem. Their thallus lacks true roots, shoots and leaves algae include unicellular plants to very big multicellular plants. They do not form embryo after sexual reproduction. Commonly, algae are colored and they can grow up to 40 or 60 meters in length.
Most algae grow in rivers, ponds, lakes and oceans. Some can live in moist places on land, mountains and near trees. A few species of algae are found on the ice in the Polar Regions and in hot water springs. Some of the blue- green algae can survive even at 70-80 degree centigrade. Some algae grow on plants and a few complete their life cycle inside some plants. Many algae are saprophytic and parasitic. The best known algae are probably the seaweed found at beaches.
About 25-30 species of algae are used as food by man. The algae porphyra of phiopcae class is a common meal in Japan. In china, Nostoc commune is used as food. In India, algae are used to prepare ice-cream, chocolate milk, gelatin and beer. Some algae are poisonous in nature and can paralyze a person.
We get carbohydrate, vitamins A, B, C, D, E and other materials from algae. Fish depend on algae for their food. Many algae obtained from oceans are rich sources of iodine, potassium and other minerals. Algae are a good fertilizer also. The red algae grow in large colonies and turn the water red. Some red algae also form islands. Reference: Children’s Science Library by A.H.Hashmi.
Different species of algae