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Amphibians are ectothermic (cold-blooded) vertebrates that do not maintain their body temperature through internal physiological processes. Their metabolic rate is low and as a result, their food and energy requirements are limited. In the adult state, they have tear ducts and movable eyelids, and most species have ears that can detect airborne ...
All body systems work in an interconnected manner to maintain the internal conditions essential to the function of the body. The skin has an important job of protecting the body and acts as the body's first line of defense against infection, temperature change, and other challenges to homeostasis. [8] [9] Its main functions include:
Derived from placoid scales, they have a thick coat of enamel, but without the underlying layer of dentin. These scales cover the fish's body with little overlapping. They are typical of gar and bichirs. Cycloid scales are small, oval-shaped scales with growth rings like the rings of a tree. They lack enamel, dentin, and a vascular bone layer.
The word skin originally only referred to dressed and tanned animal hide and the usual word for human skin was hide. Skin is a borrowing from Old Norse skinn "animal hide, fur", ultimately from the Proto-Indo-European root *sek-, meaning "to cut" (probably a reference to the fact that in those times animal hide was commonly cut off to be used as garment).
The optimum body temperature range varies with species, but is typically below that of warm-blooded animals; for many lizards, it falls in the 24–35 °C (75–95 °F) range, [74] while extreme heat-adapted species, like the American desert iguana Dipsosaurus dorsalis, can have optimal physiological temperatures in the mammalian range, between ...
Red represents a higher value (e.g. of temperature or the partial pressure of a gas) than blue so the property being transported in the channels flows from red to blue. In fish a countercurrent flow (lower diagram) of blood and water in the gills is used to extract oxygen from the environment. [6] [7] [8] All basal vertebrates breathe with gills.
The lateral line system consists of canals that run along a fish's body, connecting rows of openings (pores) through the skin and scales to the water outside the body. Small sense organs, neuromasts (inset), are positioned both at intervals along the canals, and on the surface of the body. Each hair cell contains a bundle of sensory hairs.
Scales in the central or throat region, which are in contact with the first ventral scales of a snake's body and are flanked by the chin shields, are called gular scales. The mental groove is a longitudinal groove on the underside of the head between the large, paired chin shields and continuing between the smaller gular scales.