Marine biology

Marine biology is the study of animal and plant life within waterbound ecosystems. 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 deals with those species in which life is spent only (or mainly) in the water, thus its classification is based on the environment rather than on taxonomy.

Lifeforms

Microscopic life

Microscopic life undersea is incredibly varied and still poorly understood.

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For example, at one end of the scale, the role of viruses in marine ecosystems is barely being explored even in the beginning of the 21st century.

Related Topics:
Virus - 21st century

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The role of phytoplankton is better understood due to their critical position as the most numerous primary producers on Earth. Phytoplankton fit into these categories: cyanobacteria (also called blue-green algae/bacteria), various types of algae: red, green, brown, and yellow-green, diatoms, dinoflagellates, euglenoids, coccolithophorids, cryptomonads, crysomonads, chloromonads, prasinomonads, and silicoflagellates.

Related Topics:
Phytoplankton - Algae

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Zooplankton tend to be somewhat larger, and not all in this list are microscopic. Many Protozoa are zooplankton, including dinoflagellates (yes, some of these are phytoplankton as well: the plant/animal distinction often breaks down in very small organisms), zooflagellates, foraminiferans, and radiolarians. Other zooplankton include cnidarians, ctenophores, chaetognaths, annelids such as polychaetes, molluscs, arthropods, and urochordates. Even many larger animals begin their life in the zooplankton before they become large enough to take their familiar forms. Fish larvae generally begin life as zooplankton and sea stars (a.k.a. starfish) do too, just as two examples of the many.

Related Topics:
Zooplankton - Protozoa - Larva - Starfish

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Plant life

Plant life is relatively rare undersea, most of the niche occupied by plants on land is actually occupied by macroscopic algae in the ocean, such as Sargassum and kelp.

Related Topics:
Niche - Algae - Kelp

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The plants that do survive in the sea are often found in shallow waters, such as the seagrasses (of which eelgrass, Zostera, and turtlegrass, Thalassia are examples). The intertidal zone is also a good place to find plant life in the sea, where mangroves or cordgrass might grow.

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Other sea life

Cnidarias such as Jellyfish and sea anemone, Ctenophoras, sea worms including phylums: Plathyhelminthes, Nemertea, Annelida, Sipuncula, Echiura, and the Phoronidas; Mollusca including shellfish and squid and octopus, Crustaceans, Poriferas including sponges, Bryozoa, Echinoderms including starfish, Urochordata - sea squirts or tunicates.

Related Topics:
Jellyfish - Sea anemone - Worm - Phylum - Shellfish - Squid - Octopus - Crustacean - Sponge - Bryozoa - Echinoderm - Urochordata - Sea squirt - Tunicate

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Fish

Main article: Fish

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Fishes inhabit the largest, (by volume) biome on planet earth and since they exist in a watery environment it means that very different biological functions have evolved.

Related Topics:
Biome - Evolved

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Fish anatomy includes a two chamber heart, operculum, secretory cells that produce mucous, swim bladder, scales, fins, gills, lips and eyes.

Related Topics:
Two chamber heart - Operculum - Cells - Mucous - Swim bladder - Scales - Fin - Gill - Lips - Eye

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Fish breathe under water by extracting oxygen from sea water through their gills.

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Fins are used to propel and stabilize them in their watery environment.

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Well known fish include: sardines, anchovy, tuna, clownfish (also known as anemonefish), and bottom fish which include halibut and ling cod. Predators include sharks and barracuda.

Related Topics:
Sardine - Anchovy - Tuna - Clownfish - Bottom fish - Halibut - Ling cod - Predator - Shark - Barracuda

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Marine mammals

Main article: Marine mammal

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There are five main types of marine mammals.

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• Cetaceans include toothed whales (Suborder Odontoceti), such as the Sperm Whale, dolphins, and porpoises. Cetaceans also include baleen whales (Suborder Mysticeti), such as Gray Whales, Humpback Whales, and Blue Whales.
• 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.
• Sea Otters are members of the Family Mustelidae, which includes weasels and badgers.
• Finally, Polar Bears (Family Ursidae) are sometimes considered marine mammals because of their dependence on the sea.