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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.
Prickles on a blackberry branch. In plant morphology, thorns, spines, and prickles, and in general spinose structures (sometimes called spinose teeth or spinose apical processes), are hard, rigid extensions or modifications of leaves, roots, stems, or buds with sharp, stiff ends, and generally serve the same function: physically defending plants against herbivory.
Class Amphibia (amphibians, some ancestral to the amniotes)—now a paraphyletic group; Class Synapsida (mammals and their extinct relatives) Class Sauropsida (reptiles and birds) While this traditional taxonomy is orderly, most of the groups are paraphyletic, meaning that the structure does not accurately reflect the natural evolved grouping. [47]
A neural spine sail is a large, flattish protrusion from the back of an animal formed of a sequence of extended vertebral spinous processes and associated tissues. Such structures are comparatively rare in modern animals, but have been identified in many extinct species of amphibians and amniotes. Paleontologists have proposed a number of ways ...
Metazoans do not include the sponges, which have undifferentiated cells. [16] Unlike plant cells, animal cells have neither a cell wall nor chloroplasts. Vacuoles, when present, are more in number and much smaller than those in the plant cell. The body tissues are composed of numerous types of cells, including those found in muscles, nerves and ...
Invertebrates cells fire in response to similar stimuli as mammals, such as tissue trauma, high temperature, or changes in pH. The first invertebrate in which a neuron cell was identified was the medicinal leech, Hirudo medicinalis. [14] [15] Learning and memory using nociceptors have been described in the sea hare, Aplysia.
Amphibians are in decline worldwide, with 2 out of every 5 species threatened by extinction, according to a paper published Wednesday in the scientific journal Nature. ... Food. Games. Health.
The circulatory system carries food throughout their body, but does not have red blood cells or hemoglobin for transporting oxygen. Lancelet genomes hold clues about the early evolution of vertebrates: by comparing genes from lancelets with the same genes in vertebrates, changes in gene expression, function and number as vertebrates evolved can ...