Many people believe seaweed to be a plant. Is it?
Seaweed is actually a plant-like protist, which is also known as algae. The green color is due to what pigment? Algae, like plants, obtain their energy through photosynthesis.
Seaweed is actually a type of algae.
Algae, singular alga, are members of a group of predominantly aquatic photosynthetic organisms of the kingdom Protista. The diversity of algae is extremely high. Their photosynthetic pigments are more varied than those of plants, and their cells have features not found among plants and animals. In addition to their ecological roles as oxygen producers and as the food base for almost all aquatic life, algae are economically important as a source of crude oil and as sources of food and a number of pharmaceutical and industrial products for humans.
Examples of Algae are Ulothrix, Porphyra, Spirogyra, and Fucus.
The study of algae is called phycology, and a person who studies algae is a phycologist.
Algae (singular: alga) is a diverse group of eukaryotic, photosynthetic lifeforms. Some algae, the diatoms, are single-celled. Others, such as seaweed and giant kelp are multicellular.
Most algae require a moist or watery environment; hence they are always near or inside water bodies. Anatomically, they are similar to "land plants" another group of photosynthetic organisms. Algae are considered plant-like because they contain chloroplasts and produce food through photosynthesis.
However, they lack many structural components typically present in plants, such as true stems, shoots, and leaves. Furthermore, they also do not have vascular tissues to circulate essential nutrients and water throughout their body. Some algae are also different from plants in being motile. They may move with pseudopods or flagella. Although not plants themselves, algae were probably the ancestors of plants.
Algae can reproduce either vegetatively, asexually, or sexually.
Fragmentation is the most common vegetative method of reproduction. Each fragment develops into a thallus. The filamentous thallus breaks into fragments, and each fragment is capable of forming a new thallus. Fragmentation can take place due to mechanical pressure, insect bite, etc. The common examples are Ulothrix, Spirogyra, etc.
Asexual reproduction takes place by the production of spores, called the zoospores. The zoospores are flagellated asexual structures. Zoospores move in water before they germinate to make new plants. Zoospores are normally formed under favorable conditions. Fertilization and fusion of nuclei do not take place. The reproduction takes place only by the protoplasm of the cell.
Sexual reproduction takes place by fusion of gametes of different sexuality.
| Chlorophyceae | These are called green algae, due to the presence of pigments chlorophyll a and b | Chlamydomonas, Spirogyra, and Chara |
| Phaeophyceae | Also called as brown algae, they are predominantly marine. They have chlorophyll a, c, carotenoids and xanthophyll pigments. | Dictyota, Laminaria, and Sargassum |
| Rhodophyceae | They are the red algae because of the presence of the red pigment, r-phycoerythrin | Porphyra, Gracilaria, and Gelidium |
Algae are found everywhere. They can be categorized ecologically by their habitats:
It is believed algae produce half of the earth's oxygen. They capture more of the sun’s energy and produce more oxygen than all plants combined. They play an effective role in keeping the atmospheric carbon dioxide and also using it efficiently.
The various sorts of algae play significant roles in aquatic ecology. Microscopic forms that live suspended in the water column, called phytoplankton, provide the food base for most marine food chains. The seaweeds grow mostly in shallow marine waters; some are used as human food or are harvested for useful substances such as agar or fertilizer. They form the foundation of most aquatic food webs, which support an abundance of animals.
Algae also form mutually beneficial partnerships with other organisms. For example, algae live with fungi to form lichens- plant like or branching growths that form on boulders, cliffs and tree trunks. Algae called zooxanthellae live inside the cells of reef-building coral. In both cases, the algae provide oxygen and complex nutrients to their partner, and in return, they receive protection and simple nutrients. This arrangement enables both partners to survive in conditions that they could not endure alone.
The food industry also uses some algae. Agar is obtained from Gelidium and Graciliaria and is making ice-creams and jellies. The other food supplements that are algae and which are widely used are Chlorella and Spirulina.
Algal Biofuel - Recent developments in science and technology have enabled algae to be used as a source of fuel. Global demand for petroleum products and declining environmental health has prompted the use of eco-friendly alternatives such as algal biofuel. Hence, algae fuel is an increasingly viable alternative to traditional fossil fuels. It is used to produce everything from “green” diesel to “green” jet fuel. It is similar to the other biofuels made from corn and sugar cane.
