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A true endoskeleton is derived from mesodermal tissue. In three phyla of animals, Chordata, Echinodermata and Porifera (), endoskeletons of various complexity are found.An endoskeleton may function purely for structural support (as in the case of Porifera), but often also serves as an attachment site for muscles and a mechanism for transmitting muscular forces as in chordates and echinoderms ...
Bone is also made of both mineral and carbon-based materials; the mineral-based are calcium, phosphorus, and fluoride; the carbon-based is the protein ossein. Bone also includes the mineral hydroxyapatite, "A calcium phosphate mineral which forms a hard outer covering over the collagen and protein matrix," [1] or organic material.
Pacific ocean perch is a very slow-growing species, with a low rate of natural mortality (estimated at 0.06), a relatively old age at 50% maturity (10.5 years for females in the Gulf of Alaska), and a very old maximum age of 98 years in Alaska (84 years maximum age in the Gulf of Alaska). [25]
Perch is a common name for freshwater fish from the genus Perca, which belongs to the family Percidae of the large order Perciformes. The name comes from Greek : πέρκη , romanized : perke , meaning the type species of this genus, the European perch ( P. fluviatilis ).
Elasmoid scales are thin, imbricated scales composed of a layer of dense, lamellar collagen bone called isopedine, above which is a layer of tubercles usually composed of bone, as in Eusthenopteron. The layer of dentine that was present in the first lobe-finned fish is usually reduced, as in the extant coelacanth , or entirely absent, as in ...
Bone, ivory, and antler are rarely attacked by insects, but horn is often seriously damaged by the larvae of carpet beetles and clothes moths. [7] Light, ultraviolet, and infrared. Ivory, bone, and antler should be kept away from bright light such as spotlights or direct sunlight. Bright light can increase the surface temperature of the object.
The alleged failings in the oil clean-up come as Shell prepares to sell its Nigerian subsidiary, the SPDC, to Renaissance Africa, a consortium of local and international companies.
Aristotle (ca. 340 B.C.) may have been the first scientist to speculate on the use of hard parts of fishes to determine age, stating in Historica Animalium that “the age of a scaly fish may be told by the size and hardness of its scales.” [4] However, it was not until the development of the microscope that more detailed studies were performed on the structure of scales. [5]