Algae

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A seaweed (Laurencia) up close: the "branches" are multicellular and only about 1 mm thick. Much smaller algae are seen growing attached to the structure extending upwards in the lower right quarter

Algal blooms can present problems for ecosystems and human society

Algae (singular alga) encompass several groups of relatively simple, eukaryotic, living aquatic organisms that capture light energy through photosynthesis, using it to convert inorganic substances into organic matter.

Algae are photosynthetic organisms that occur in most habitats. Algae varies from small, single-celled forms to complex multicellular forms, such as the giant kelps that grow to 65 meters in length. The US Algal Collection is represented by almost 300,000 accessioned and inventoried herbarium specimens.[1]

Although algae have conventionally been regarded as simple plants, they actually span more than one domain, including both Eukaryota and Bacteria (see Blue-green algae), as well as more than one kingdom, including plants and protists, the latter being traditionally considered more animal-like (see 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-cell organisms to multicellular organisms, some with fairly complex differentiated form and (if marine) called seaweeds. All lack leaves, roots, flowers, seeds and other organ structures that characterize higher plants (vascular 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 byproduct of photosynthesis, unlike non-cyanobacterial photosynthetic bacteria. It is estimated that algae produce about 73 to 87 percent of the net global production of oxygen - which is available to humans and other terrestrial animals for respiration.

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 adaptations to live on land. Algae can endure dryness and other conditions in symbiosis with a fungi 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 chains. In very high densities (so-called algal blooms) these algae may discolor the water and outcompete or poison other life forms. Seaweeds 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 marine and freshwater algae is called phycology or algology.

External links

• AlgaeBase - a comprehensive database of over 35,000 Algae (132,000 names), including seaweeds, with over 5000 images and some 40,000 references.
• www.phyco.org; a wiki-based site that is focused on energy production from algae.
• biodieselnow.com biodiesel production-biodiesel from algae
• Australian freshwater algae - Sydney Botanic Gardens
• Learn about Algae & Algal Blooms - Rural Chemical Industries (Aust.) Pty Ltd.
• Harmful Algal Blooms - "Red tide" - National Office for Marine Biotoxins and Harmful Algal Blooms, USA.
• Patent ListingAlgae Related United States Patents
• Algae Section, National Museum of Natural History - Smithsonian Institution
• www.plantphysiol.org
• Cyanosite
• Algae Growth
• Blanket Weed
• British Phycological Society
• Seaweed site by Michael Guiry
• http://www.botanicgardens.ie/educ/vis12.htm
• http://www.ucmp.berkeley.edu/protista/rhodophyta.html - Introduction to Rhodophyta]
• http://www.botany.uwc.ac.za/algae/
• http://www.marlin.ac.uk - Marlin
• http://www.mbari.org/staff/conn/botany/flora/reds.htm - Monterey Bay Flora
• http://www.mbari.org/staff/conn/botany/flora/browns.htm - Monterey Bay Flora
• http://www.mbari.org/staff/conn/botany/flora/green.htm - Monterey Bay Flora

References

Identification

• Abbott, I.A. and Hollenberg, G.J. 1976. Marine Algae of California. Stanford University Press, California. ISBN 0-8047-0867-3
• Brodie, J.A. and Irvine, L.M. 2003. Seaweeds of the British Isles. Volume 1 Part 3B. The Natural History Museum, London. ISBN 1 898298 87 4
• Burrows, E.M. 1991. Seaweeds of the British Isles. Volume 2. British Museum (Natural History), London. ISBN 0-565-00981-8
• Christensen, T. 1987. Seaweeds of the British Isles. Tribophyceae. Volume 4. British Museum (Natural History), London. ISBN 0-565-00980-X
• Dixon, P.S. and Irvine, L.M. 1977. Seaweeds of the British Isles. Volume 1. Part 1. Introduction, Nemaliales, Gigartinales. British Museum (Natural History), London. ISBN 0 565 00781 5
• Irvine, L.M. 1983. Seaweeds of the British Isles. Volume 1, Part 2A. British Museum (Natural History), London. ISBN 0-565-00871-4
• Irvine, L.M. and Chamberlain, Y.M. 1994. Seaweeds of the British Isles. Volume 1 Part 2B. The Natural History Museum, London. ISBN 0 11 310016 7
• Fletcher, R.L. 1987. Seaweeds of the British Isles. Volume 3 Part 1. British Museum (Natural History), London. ISBN 0-565-00992-3
• John, D.M., Whitton, B.A. and Brook, J.A. (Eds.) 2002. The Freshwater Algal Flora of the British Isles. Cambridge University Press, UK. ISBN 0 521 77051 3
• Stegenga, H., Bolton, J.J. and Anderson, R.J.1997. Seaweeds of the South African west coast. Boltus Herbarium, University of Cape Town. ISBN 0-7992-1793-x
• Taylor, W.R. 1957. Marine algae of the north-eastern coasts of North America. Revised edition. University of Michigan Press. Ann Arbor.

General

• Chapman, V.J. 1950.p.36. Seaweeds and their Uses. Methuen & Co. Ltd., London.
• Guiry, M.D. and Blunden, G. (Eds) 1991. Seaweed Resources in Europe: Uses and Potential. John Wiley & Sons. ISBN 0-471-92947-6
• Lembi, C.A. and Waaland, J.R. (Eds.) 1988. Algae and Human Affairs. Cambridge University Press, Cambridge. ISBN 0-521-32115-8

Image:AlgaeTree.png | Image:Seaweed.jpg | Classification of algae | Forms of algae | Algae and symbioses | Life-cycle of algae | Numbers and distribution of algae | Distribution of algae | Uses of algae | Algae History of Phycology | Biological Exposure Scale of algae | Examples of algae | Algae Trivia |

Facts about AlgaeRDF feed

Part	Classification of algae  +, Forms of algae  +, Life-cycle of algae  +, Numbers and distribution of algae  +, Distribution of algae  +, and Algae History of Phycology  +
Related concept	Algae and symbioses  +, Biological Exposure Scale of algae  +, and Algae Trivia  +
See	+,   +, and Examples of algae  +
Used as	Uses of algae  +