Under the Sea....................

Marine biology

From Wikipedia, the free encyclopedia

Only 29 percent of the Earth's surface is land. The rest is ocean, home to marine life. The oceans average nearly four kilometres in depth and are fringed with coastlines that run for 360,000 kilometres.^[1][2]

Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on theenvironment rather than on taxonomy. Marine biology differs from marine ecology as marine ecology is focused on how organisms interact with each other and the environment, while biology is the study of the organisms themselves.

A large proportion of all life on Earth exists in the ocean. Exactly how large the proportion is unknown, since many ocean species are still to be discovered. The ocean is a complex three-dimensional world^[3] covering about 71% of the Earth's surface. The habitats studied in marine biology include everything from the tiny layers of surface water in which organisms and abiotic items may be trapped in surface tension between the ocean and atmosphere, to the depths of the oceanic trenches, sometimes 10,000 meters or more beneath the surface of the ocean. Specific habitats include coral reefs, kelp forests, seagrass meadows, the surrounds of seamounts and thermal vents, tidepools, muddy, sandy and rocky bottoms, and the open ocean (pelagic) zone, where solid objects are rare and the surface of the water is the only visible boundary. The organisms studied range from microscopic phytoplankton and zooplankton to huge cetaceans (whales) 30 meters (98 feet) in length.

Marine life is a vast resource, providing food, medicine, and raw materials, in addition to helping to support recreation and tourism all over the world. At a fundamental level, marine life helps determine the very nature of our planet. Marine organisms contribute significantly to the oxygen cycle, and are involved in the regulation of the Earth's climate.^[4] Shorelines are in part shaped and protected by marine life, and some marine organisms even help create new land.^[5]

Many species are economically important to humans, including food fish (both finfish and shellfish). It is also becoming understood that the well-being of marine organisms and other organisms are linked in very fundamental ways. The human body of knowledge regarding the relationship between life in the sea and important cycles is rapidly growing, with new discoveries being made nearly every day. These cycles include those of matter (such as the carbon cycle) and of air (such as Earth's respiration, and movement of energy through ecosystems including the ocean). Large areas beneath the ocean surface still remain effectively unexplored.

Contents

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• 1 History
• 2 Subfields
  • 2.1 Related fields
• 3 Animals
  • 3.1 Birds
  • 3.2 Fish
  • 3.3 Invertebrates
  • 3.4 Mammals
  • 3.5 Reptiles
• 4 Fungi
• 5 Plants and algae
• 6 Microscopic life
• 7 Marine habitats
  • 7.1 Intertidal and shore
  • 7.2 Reefs
  • 7.3 Open ocean
  • 7.4 Deep sea and trenches
• 8 Distribution factors
• 9 See also
• 10 Lists
• 11 References
• 12 Further references
• 13 External links

History[edit]

HMS Challenger during its pioneer expedition of 1872–76

Main article: History of marine biology

Early instances of the study of marine biology trace back to Aristotle (384–322 BC) who made several contributions which laid the foundation for many future discoveries and were the first big step in the early exploration period of the ocean and marine life.^[6] In 1768, Samuel Gottlieb Gmelin (1744–1774) published the Historia Fucorum, the first book dedicated to marine algae and the first work on marine biology to use the then new binomial nomenclature of Linnaeus. It included elaborate illustrations of seaweed and marine algae on folded leaves.^[7][8] The British naturalist Edward Forbes (1815–1854) is generally regarded as the founder of the science of marine biology.^[9] The pace of oceanographic and marine biology studies quickly accelerated during the course of the 19th century.

The observations made in the first studies of marine biology fuelled the age of discovery and exploration that followed. During this time, a vast amount of knowledge was gained about the life that exists in the oceans of the world. Many voyages contributed significantly to this pool of knowledge. Among the most significant were the voyages of the HMS Beagle where Charles Darwin came up with his theories of evolution and on the formation of coral reefs.^[10] Another important expedition was undertaken by HMSChallenger, where findings were made of unexpectedly high species diversity among fauna stimulating much theorizing by population ecologists on how such varieties of life could be maintained in what was thought to be such a hostile environment.^[11] This era was important for the history of marine biology but naturalists were still limited in their studies because they lacked technology that would allow them to adequately examine species that lived in deep parts of the oceans.

The creation of marine laboratories was important because it allowed marine biologists to conduct research and process their specimens from expeditions. The oldest marine laboratory in the world, Station biologique de Roscoff, was established in France in 1872. In the United States, the Scripps Institution of Oceanography dates back to 1903, while the prominent Woods Hole Oceanographic Institute was founded in 1930.^[12] The development of technology such as sound navigation ranging, scuba diving gear, submersibles and remotely operated vehicles allowed marine biologists to discover and explore life in deep oceans that was once thought to not exist.^[13]

Subfields[edit]

Coral reefs form complex marine ecosystems with tremendous biodiversity.

The marine ecosystem is large, and thus there are many sub-fields of marine biology. Most involve studying specializations of particular animal groups, such asphycology, invertebrate zoology and ichthyology.

Other subfields study the physical effects of continual immersion in sea water and the ocean in general, adaptation to a salty environment, and the effects of changing various oceanic properties on marine life. A subfield of marine biology studies the relationships between oceans and ocean life, and global warming and environmental issues (such as carbon dioxide displacement).

Recent marine biotechnology has focused largely on marine biomolecules, especially proteins, that may have uses in medicine or engineering. Marine environments are the home to many exotic biological materials that may inspire biomimetic materials.

Related fields[edit]

Marine biology is a branch of biology and is closely linked to oceanography. It also encompasses many ideas from ecology. Fisheries science and marine conservationcan be considered partial offshoots of marine biology (as well as environmental studies). Marine Chemistry, Physical oceanography and Atmospheric sciences are closely related to this field.

Animals[edit]

Birds[edit]

Main article: Seabird

Birds adapted to living in the marine environment are often referred to as seabirds. Examples include albatross, penguins, gannets, and auks. Although they spend most of their lives in the ocean, species such asgulls can often be found thousands of miles inland.

Fish[edit]

Main article: Fish

See also: Diversity of fish

Fish anatomy includes a two-chambered heart, operculum, swim bladder, scales, fins, lips, eyes and secretory cells that produce mucous. Fish breathe by extracting oxygen from water through their gills. Fins propel and stabilize the fish in the water. Many fish fall under two major categories - Elasmobranchii and Teleostei.

A reported 32,700 species of fish have been described (as of December 2013),^[14] more than the combined total of all other vertebrates. About 60% of fish species are saltwater fish.^[15]

A crown-of-thorns starfish.

Invertebrates[edit]

Main article: Marine invertebrates

As on land, invertebrates make up a huge portion of all life in the sea. Invertebrate sea life includes Cnidaria such as jellyfish and sea anemones; Ctenophora; sea wormsincluding the phyla Platyhelminthes, Nemertea, Annelida, Sipuncula, Echiura, Chaetognatha, and Phoronida; Mollusca including shellfish, squid, octopus; Arthropoda includingChelicerata and Crustacea; Porifera; Bryozoa; Echinodermata including starfish; and Urochordata including sea squirts or tunicates.

Sea otters.

Mammals[edit]

Main article: Marine mammal

There are five main types of marine mammals.

• Cetaceans include toothed whales (Suborder Odontoceti), such as the Sperm Whale, dolphins, and porpoises such as the Dall's porpoise. Cetaceans also include baleen whales (Suborder Mysticeti), such as the Gray Whale, Humpback Whale, and Blue Whale.
• Sirenians include manatees, the Dugong, and the extinct Steller's Sea Cow.
• Seals (Family Phocidae), sea lions (Family Otariidae - which also include the fur seals), and the Walrus (Family Odobenidae) are all considered pinnipeds.
• The Sea Otter is a member of the Family Mustelidae, which includes weasels and badgers.
• The Polar Bear (Family Ursidae) is sometimes considered a marine mammal because of its dependence on the sea.