Information AboutAlgae |
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Algae (singular ''alga'') encompass several different groups of living organisms that capture light energy through Photosynthesis , converting inorganic substances into simple sugars using the captured energy. Algae have been traditionally regarded as simple Plant s, and some are closely related to the Higher Plants . Others appear to represent different Protist groups, alongside other organisms that are traditionally considered more animal-like (that is, Protozoa ). Thus algae do not represent a single evolutionary direction or line, but a level of organization that may have developed several times in the early history of life on earth. Algae range from single-celled organisms to multi-cellular organisms, some with fairly complex differentiated form and (if marine) called Seaweed s. All lack Leaves , Root s, Flower s, and other organ structures that characterize higher plants. They are distinguished from other Protozoa in that they are Photoautotrophic , although this is not a hard and fast distinction as some groups contain members that are Mixotrophic , deriving energy both from photosynthesis and uptake of organic carbon either by Osmotrophy , Myzotrophy , or Phagotrophy . Some unicellular species rely entirely on external energy sources and have reduced or lost their photosynthetic apparatus. All algae have photosynthetic machinery ultimately derived from the Cyanobacteria , and so produce Oxygen as a by-product of photosynthesis, unlike non-cyanobacterial photosynthetic bacteria. Algae are usually found in damp places or bodies of water and thus are common in terrestrial as well as aquatic environments. However, terrestrial algae are usually rather inconspicuous and far more common in moist, tropical regions than dry ones, because algae lack vascular tissues and other adaptions to live on land. Algae can endure dryness and other conditions in symbiosis with a fungus as Lichen . 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 Chain s. In very high densities (so-called Algal Bloom s) these algae may discolor the water and outcompete or poison other life forms. Seaweed s grow mostly in shallow marine waters. Some are used as human food or harvested for useful substances such as Agar or fertilizer. The study of algae is called Phycology or algology. RELATIONSHIPS AMONG ALGAL GROUPS Prokaryotic algae Traditionally the are some of the oldest organisms to appear in the Fossil Record , dating back about 3.8 billion years ( Precambrian ). Ancient cyanobacteria likely produced much of the Oxygen in the Earth's atmosphere. Cyanobacteria can be unicellular, colonial, or filamentous. They have a Prokaryotic cell structure typical of bacteria and conduct photosynthesis directly within the Cytoplasm , rather than in specialized organelles. Some filamentous Blue-green Algae have specialized cells, termed heterocysts, in which Nitrogen Fixation occurs. {Link without Title} Eukaryotic algae All other algae are Eukaryote s and conduct photosynthesis within membrane-bound structures (organelles) called Chloroplast s. Chloroplasts contain DNA and are similar in structure to cyanobacteria, presumably representing reduced cyanobacterial Endosymbionts . The exact nature of the chloroplasts is different among the different lines of algae, reflecting different endosymbiotic events. There are three groups ( Archaeplastida ) that have ''primary'' chloroplasts:
In these groups, the chloroplast is surrounded by two membranes and probably developed through a single endosymbiosis. The chloroplasts of red algae have a more or less typical cyanobacterial pigmentation, while those of the green alga have chloroplasts with chlorophyll ''a'' and ''b'', the latter found in some cyanobacteria and not most. Higher plants are pigmented similarly to green algae and probably developed from them. Two other groups of algae have green chloroplasts containing chlorophyll ''b'':
These are surrounded by three and four membranes, respectively, and were probably retained from an ingested green alga. Those of the chlorarchniophytes contain a small nucleomorph, which is the remnant of the alga's Nucleus . It has been suggested that the euglenid chloroplasts only have three membranes because they were acquired through Myzocytosis rather than Phagocytosis . The remaining algae all have chloroplasts containing chlorophylls ''a'' and ''c''. The latter chlorophyll type is not known from any prokaryotes or primary chloroplasts, but genetic similarities with the red algae suggest a relationship there. These groups include:
In the first three of these groups ( Chromista ), the chloroplast has four membranes, retaining a nucleomorph in cryptomonads, and they likely share a common pigmented ancestor. The typical dinoflagellate chloroplast has three membranes, but there is considerable diversity in chloroplasts among the group, as some members have acquired theirs from different sources. The Apicomplexa , a group of closely related parasites, also have Plastid s though not actual chloroplasts, which appear to have a common origin with those of the dinoflagellates. Note many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost them entirely. FORMS OF ALGAE Most of the simpler algae are unicellular Flagellate s or Amoeboid s, but colonial and non-motile forms have developed independently among several of the groups. Some of the more common organizational levels, more than one of which may occur in the Life Cycle of a species, are:
In three lines even higher levels of organization have been reached, leading to organisms with full tissue differentiation. These are the Brown Alga e—some of which may reach 70 m in length ( Kelp s)—the Red Alga e, and the Green Alga e. The most complex forms are found among the green algae (see Charales ), in a lineage that eventually led to the higher land plants. The point where these non-algal plants begin and algae stop is usually taken to be the presence of reproductive organs with protective cell layers, a characteristic not found in the other alga groups. ALGAE AND SYMBIOSES Some species of algae form Symbiotic Relationships with other organisms. In these symbioses, the algae supply photosynthates (organic substances) to the host organism providing protection to the algal cells. The host organism derives some or all of its energy requirements from the alga. Examples include:
USES OF ALGAE Algae are used by man in a great many ways. Because many species are aquatic and microscopic, they are cultured in clear tanks or ponds and either harvested or used to treat effluents pumped through the ponds. Algaculture on a large scale is an important type of Aquaculture in some places. Energy source
pmb.berkeley.edu Pollution control
Nutritional value of algae
www.spirulinasource.com www.cfsan.fda.gov FDA on algal-oil use in food products The natural Pigment s produced by algae can be used as an alternative to chemical Dyes and coloring agents. {Link without Title} Many of the paper products used today are not recyclable because of the chemical inks that they use, paper recyclers have found that inks made from algae are much easier to break down. There is also much interest in the food industry into replacing the coloring agents that are currently used with coloring derived from algal pigments. SEE ALSO
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