THE DEFINITION of algae is a single or multi-cellular organism that has no roots, stems or leaves and is often found in water. Any of numerous groups of chlorophyllcontaining, mainly aquaticeukaryotic organisms ranging from microscopic singlecelled forms tomulticellular forms 100 feet (30 meters) or more long, distinguishedfrom plants by the absence of true roots, stems, and leaves and by lack of non-reproductive cells in the reproductive structures: classifiedinto the six phyla Euglenophyta, Crysophyta, Pyrrophyta, Chlorophyta,Phaeophyta, and Rhodophyta.
Types of Algae
Green algae range in size from microscopic to large plants, and can be single celled, colonial, or filamentous. Some of the single celled and colonial green algae have small tails or “flagella” attached to each cell, which they use to swim. However many green algae are non-motile. Green algae may be either planktonic or attached. They show the greatest diversity of shapes, sizes and species of any group of freshwater algae. Green chloroplasts are frequently observable within the cells of green algae when looked at under a microscope.
Blue- green Algae
Blue-green algae or Cyanobacteria are microscopic cells that grow naturally in Australian fresh and salt waters. They are a type of bacteria, but in some ways act like plants by using sunlight to manufacture carbohydrates from carbon dioxide and water, a process known as photosynthesis. In doing so, they release oxygen. They grow in dams, rivers, creeks, reservoirs, lakes and even hot springs.
They are commonly found in freshwater streams and ponds, when they may form a green scum on the surfaces of storages, irrigation bays or drainage ditches. They are green and sometimes red. They occasionally form green or red powdery films on the surface of ponds or dams. The surface colour can change from red to green in a few hours. Euglena is free swimming in ponds and lakes and is also found in mud rich in organic matter. There are 152 reported species 33 known to occur in Australia.
Unicellular organisms of the kingdom protista, characterized by a silica shell of often intricate and beautiful sculpturing. Most diatoms exist singly, although some join to form colonies. They are usually yellowish or brownish, and are found in fresh- and saltwater, in moist soil, and on the moist surface of plants. Fresh-water and marine diatoms appear in greatest abundance early in the year as part of the phenomenon known as the spring bloom, which occurs as a result of the availability of both light and (winter-regenerated) nutrients. They reproduce asexually by cell division.Chlorophyta
Division of the kingdom of protista consisting of the photosynthetic organism commonly known as green algae. The various species can be unicellular, multi-cellular, Coenocytic (having more than one nucleus in a cell), or colonial. Chlorophyta are largely aquatic or marine, a few types are terrestrial, occurring on moist soil, on the trunks of trees, on moist rocks and in snow banks. Various species are highly specialized.
Some species are heterotrophic, but many are photosynthetic organisms containing chlorophyll. Various other pigments may mask the green of these chlorophylls. Other species are endosymbionts of marine animals and protozoa, and play an important part in the biology of coral reefs. Other dino-flagellates are colorless predators on other protozoa, and a few forms are parasitic.
Phylum of prokaryotic aquatic bacteria that obtain their energy through photosynthesis. They are often referred to as blue-green algae, even though it is now known that they are not related to any of the other algal groups, which are all eukaryotes. Cyanobacteria may be single-celled or colonial. Depending upon the species and environmental conditions, colonies may form filaments, sheets or ever hollow balls.
phylum of the kingdom protista consisting of those organisms commonly called brown algae. Many of the worlds familiar seaweeds are members of Phaeophyta. Like the chrysophytes brown algae derive their color from the presence, in the cell chloroplasts, of several brownish carotenoid pigments, as fucoxathin. With only a few exceptions, brown algae are marine, growing in the colder oceans of the world, many in the tidal zone, where they are subjected to great stress from wave action; others grow in deep water. There are approximately 1500 species of Phaeophyta.
Habit and Habitats
Numerous algal species occur in nature. They are commonly found in water (Fresh, marine or brackish). They may either be suspended (Planktonic) or attached and living at the bottom (Benthic). Plankton consists of free-floating microscopic aquatic organisms. Phytoplankton is made up of algae and small plants while zooplankton consists of animal organisms. Some algae grow on damp soil, moist rocks, wood and on tree bark. Algae also exist as endosymbionts in various plants and protozoa. Algae associate with fungi to form Lichens.
They range in size from the tiny flagellate Micromonas that is 1 micrometer (0.00004 inch) in diameter to giant kelps that reach 60 metres (200 feet) in length.
Algal Cell Structure
Algae are eukaryotic cells, or cells that contain a nucleus, which makes them slightly more complex than bacteria. They also contain chloroplasts, which are structures that generate energy for the cell through photosynthesis. Other structures that algae may have vary greatly. Some algae have silica exoskeletons, flagella for movement or other structures. The pigment used photosynthesis can even vary, resulting in algae that appear green, red, or brown.
Classification of Algae
The classification is the scientific organization of the organisms in a hierarchical series of groups on the basis of common characters. Algae are divided into different phylum on the basis of two factors i.e. Pigmentation and Storage material. Algae are classified into different division (phylum) namely Chlorophyta, Charophyta, Phaeophyta, Rhodophyta, Bacillariophyta, Xanthophyta, and Euglenophyta.
Economic importance of Algae
Algae have beneficial and harmful aspects as are following:
Beneficial aspects of algae
Algae have various beneficial aspects as they are source of food, they have utilization in industry, nitrogen fixation, fertilizers, minerals, and also act as primary producers.
Harmful aspects of algae
Despite of so many beneficial activities of algae it brings loss of life and economy to the human beings animals etc. Some of the harmful aspects of algae are contamination of water reservoirs, water blooms, death to living organisms, diseases to human beings, and parasitic activities.
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