Juvenile Justice System
Your Basic Sea Animals
Your Basic Sea Animals
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and porpoises.
Whales, dolphins and porpoises belong to the order Cetartiodactyla, which consists of even-toed ungulates. Their closest non-cetacean living relatives are the hippopotamuses, from which they and other cetaceans diverged about 54 million years ago.
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.
However, the term "shark" has also been used to refer to all extinct members of Chondrichthyes with a shark-like morphology, such as hybodonts and xenacanths.
A dolphin is an aquatic mammal within the infraorder Cetacea. There are 40 extant species named as dolphins.
Dolphins range in size from the 1.7-metre-long (5 ft 7 in) and 50-kilogram (110-pound) Maui's dolphin to the 9.5 m (31 ft 2 in) and 10-tonne (11-short-ton) orca. Various species of dolphins exhibit sexual dimorphism where the males are larger than females.
Pinnipeds (pronounced /ˈpɪnɪˌpɛdz/), commonly known as seals,[a] are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals.
There are 34 extant species of pinnipeds, and more than 50 extinct species have been described from fossils.
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (/ˌæstəˈrɔɪdiə/). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars.
About 1,900 species of starfish occur on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at 6,000 m (20,000 ft) below the surface.
An octopus is a soft-bodied, eight-limbed mollusc of the order Octopoda.
The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids.
A seahorse (also written sea-horse and sea horse) is any of 46 species of small marine fish in the genus Hippocampus. "Hippocampus" comes from the Ancient Greek hippókampos, itself from híppos meaning "horse" and kámpos meaning "sea monster" or "sea animal".
Having a head and neck suggestive of a horse, seahorses also feature segmented bony armour, an upright posture and a curled prehensile tail.
Sea urchins are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to 5,000 meters (16,000 ft; 2,700 fathoms).
The spherical, hard shells (tests) of sea urchins are round and spiny, ranging in diameter from 3 to 10 cm (1 to 4 in). Sea urchins move slowly, crawling with tube feet, and also propel themselves with their spines.
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria.
Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion.