EndoskeletonAn endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue. An endoskeleton is a skeleton that is on the inside of a body, like humans, dogs, or some fish. The endoskeleton develops within the skin or in the deeper body tissues. The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage). During early embryonic development the endoskeleton is composed of notochord and cartilage.
AmbulacrariaAmbulacraria ,aembjuːl@'krɛəri@, or Coelomopora siːl@'mQp@r@, is a clade of invertebrate phyla that includes echinoderms and hemichordates; a member of this group is called an ambulacrarian. Phylogenetic analysis suggests the echinoderms and hemichordates separated around 533 million years ago. The Ambulacraria are part of the deuterostomes, a larger clade that also includes the Chordata, Vetulicolia. The two living clades with representative organisms are: Echinodermata (sea stars, sea urchins, brittle stars, sea cucumbers, feather stars, sea lilies, etc.
Tube feetTube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on brittle stars, and have only a feeding function in feather stars. They are part of the water vascular system. Tube feet function in locomotion, feeding, and respiration. The tube feet in a starfish are arranged in grooves along the arms. They operate through hydraulic pressure.
Urchin barrenAn urchin barren is commonly defined as an urchin-dominated area with little or no kelp. Urchin grazing pressure on kelp is a direct and observable cause of a "barren" area. However, determining which factors contribute to shifting a kelp bed to an urchin barrens is a complex problem and remains a matter of debate among scientists. Loss of "top" predators, particularly the historic hunting of sea otters (Enhydra lutris) , has often been cited as a cause of these barrens.
Epidermis (zoology)In zoology, the epidermis is an epithelium (sheet of cells) that covers the body of a eumetazoan (animal more complex than a sponge). Eumetazoa have a cavity lined with a similar epithelium, the gastrodermis, which forms a boundary with the epidermis at the mouth. Sponges have no epithelium, and therefore no epidermis or gastrodermis. The epidermis of a more complex invertebrate is just one layer deep, and may be protected by a non-cellular cuticle. The epidermis of a higher vertebrate has many layers, and the outer layers are reinforced with keratin and then die.
Sand dollarSand dollars (also known as sea cookies or snapper biscuits in New Zealand, or pansy shells in South Africa) are species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits. Sand dollars can also be called "sand cakes" or "cake urchins". Sand dollars are small in size, averaging from three to four inches. As with all members of the order Clypeasteroida, they possess a rigid skeleton called a test.
Fragmentation (reproduction)Fragmentation in multicellular or colonial organisms is a form of asexual reproduction or cloning, where an organism is split into fragments. Each of these fragments develops into mature, fully grown individuals that are clones of the original organism. The organism may develop specific organs or zones to shed or be easily broken off. If the splitting occurs without the prior preparation of the organism, both fragments must be able to regenerate the complete organism for it to function as reproduction.
Crown-of-thorns starfishThe crown-of-thorns starfish (frequently abbreviated to COTS), Acanthaster planci, is a large starfish that preys upon hard, or stony, coral polyps (Scleractinia). The crown-of-thorns starfish receives its name from venomous thorn-like spines that cover its upper surface, resembling the biblical crown of thorns. It is one of the largest starfish in the world. A. planci has a very wide Indo-Pacific distribution.
