A male whale shark at the Georgia Aquarium.

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Killer whales (orcas) are highly visible marine apex predators that hunt many large species. But most biological activity in the ocean takes place with microscopic marine organisms that cannot be seen individually with the naked eye, such as marine bacteria and phytoplankton.

Marine life, sea life, or ocean life is the plants, animals, and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. Marine organisms, mostly microorganisms, produce oxygen and sequester carbon. Marine life, in part, shape and protect shorelines, and some marine organisms even help create new land (e.g. coral building reefs).

Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters, including breathing tubes as in mollusc siphons. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine mammals (e.g. dolphins, whales, otters, and seals) need to surface periodically to breathe air. (Full article...)


Marine biology is the scientific study of the biology of marine life, organisms that inhabit the sea. 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 the environment rather than on taxonomy. (Full article...)

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A grey reef shark
(Carcharhinus amblyrhynchos)

Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the Batoidea (rays and kin). Some sources extend the term "shark" as an informal category including extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as Cladoselache and Doliodus first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (selachimorphs) are known from the Early Jurassic around 200 million years ago, with the oldest known member being Agaleus, though records of true sharks may extend back as far as the Permian.

Sharks range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species that is only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length. They are found in all seas and are common to depths up to 2,000 metres (6,600 ft). They generally do not live in freshwater, although there are a few known exceptions, such as the bull shark and the river sharks, which can be found in both seawater and freshwater, and the Ganges shark, which lives only in freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth. (Full article...)

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  • ... Sharks never stop growing; when they reach adulthood, they just slow down.
  • ... newborn cetacean calves ‘suckle’ three to four times each hour and will suckle from their mothers for six months or more.
  • ... In sand tiger sharks and several other species, the biggest, strongest pups eat the others while still inside their mother’s body.
  • ... If sharks don’t keep on swimming they sink to the seabed.
  • ... Epaulette sharks are often found in rock pools. They can move from one pool to another across dry land, by dragging themselves with their strong pectoral fins.
  • ... that the Southern Right Whale got its name because it was the ‘right’ whale to kill? Because they swim slowly, close to the shore and float when killed, the whalers thought them the right whales to kill!

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The Double-crested Cormorant (Phalacrocorax auritus) is a North American member of the cormorant family of seabirds. Its name is derived from the Greek words phalakros (bald) and kora (raven), and the Latin auritus (eared). Folk names of this bird include Crow-duck, Farallon Cormorant, Florida Cormorant, lawyer, shag, and Taunton turkey.

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