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Amphibians have soft bodies with thin skins, and lack claws, defensive armour, or spines. Nevertheless, they have evolved various defence mechanisms to keep themselves alive. The first line of defence in salamanders and frogs is the mucous secretion that they produce. This keeps their skin moist and makes them slippery and difficult to grip.
For instance, descendants of the first reptiles include modern reptiles, mammals and birds; the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; a group of amphibians, the labyrinthodonts, have given rise to the reptiles (traditionally including the mammal-like synapsids), which in ...
Marine vertebrates also have a far more centralized nervous system than marine invertebrates, with most of the higher functions cephalized and monopolized by the brain; and most of them have evolved myelinated central and peripheral nerve system, which increases conduction speeds significantly.
Scientists found that members of the new species are smaller than their offshore common bottlenose counterparts, eat different fish and have spines adapted to navigating the tight spaces of rivers ...
Hatching takes place after 10 days of gestation; the young echidna, called a puggle, [23] [24] born larval and fetus-like, then sucks milk from the pores of the two milk patches (monotremes have no teats) and remains in the pouch for 45 to 55 days, [25] at which time it starts to develop spines. The mother digs a nursery burrow and deposits the ...
Frogs have maxillary teeth along their upper jaw which are used to hold food before it is swallowed. These teeth are very weak, and cannot be used to chew or catch and harm agile prey. Instead, the frog uses its sticky, cleft tongue to catch insects and other small moving prey.
Many vertebrates are limbless, limb-reduced, or apodous, with a body plan consisting of a head and vertebral column, but no adjoining limbs such as legs or fins. Jawless fish are limbless but may have preceded the evolution of vertebrate limbs, whereas numerous reptile and amphibian lineages – and some eels and eel-like fish – independently lost their limbs.
They have a rigid, usually spherical body bearing moveable spines, which give the class the name Echinoidea (from the Greek ἐχῖνος ekhinos 'spine'). [5] The name urchin is an old word for hedgehog , which sea urchins resemble; they have archaically been called sea hedgehogs .