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In evolutionary terms, this means the opioid receptor sub-types are already present in amphibians, although the differences between these are less pronounced than in mammals. [45] Sequence comparisons show that the amphibian opioid receptors are highly conserved (70-84% similar to mammals) and are expressed in the central nervous system (CNS ...
Vertebrate zoology is the biological discipline that consists of the study of Vertebrate animals, i.e., animals with a backbone, such as fish, amphibians, reptiles, birds and mammals. Many natural history museums have departments named Vertebrate Zoology.
The high degree of overlap between marine mammal species richness and areas of human impact on the environment is of concern. [5] Most marine mammals, such as seals and sea otters, inhabit the coast. Seals, however, also use a number of terrestrial habitats, both continental and island.
Limbs in vertebrates are occasionally organized into stylopod (relating to the humerus and femur), zeugopod (relating to the radius and tibia, along with associated structures) and autopod (relating to digits) categories, although anatomically, the evolutionary differences between these groups in early tetrapods tends to be vague. [2] [20]
The first amphibians appeared on land in the Carboniferous. During the Triassic , mammals and dinosaurs appeared, the latter giving rise to birds in the Jurassic . Extant species are roughly equally divided between fishes of all kinds, and tetrapods.
Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny [ 1 ] (the evolution of species). The science began in the classical era , continuing in the early modern period with work by Pierre Belon who noted the similarities of the skeletons ...
While the early amniotes resembled their amphibian ancestors in many respects, a key difference was the lack of an otic notch at the back margin of the skull roof. In their ancestors, this notch held a spiracle , an unnecessary structure in an animal without an aquatic larval stage. [ 25 ]
Marine mammals are aquatic mammals that rely on the ocean for their existence. They include animals such as sea lions, whales, dugongs, sea otters and polar bears. Like other aquatic mammals, they do not represent a biological grouping. [26] The humpback whale is a fully aquatic marine mammal.