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Animals also cool themselves by gaping the mouth, which cools by evaporation from the mouth lining. [109] By these means, the temperature range of crocodilians is usually maintained between 25 and 35 °C (77 and 95 °F), and mainly stays in the range 30 to 33 °C (86 to 91 °F).
The evolution of biological complexity is one important outcome of the process of evolution. [1] Evolution has produced some remarkably complex organisms – although the actual level of complexity is very hard to define or measure accurately in biology, with properties such as gene content, the number of cell types or morphology all proposed as possible metrics.
The concept of the three great evolutionary faunas of marine animals from the Cambrian to the present (that is, the entire Phanerozoic) was introduced by Jack Sepkoski in 1981 using factor analysis of the fossil record. [1]
Beginning of animal evolution. [54] [55] 720–630 Ma Possible global glaciation [56] [57] which increased the atmospheric oxygen and decreased carbon dioxide, and was either caused by land plant evolution [58] or resulted in it. [59] Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution. [60] [61] [62 ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 7 January 2025. Taxonomic group of semi-aquatic mammals Pinnipeds Temporal range: Latest Oligocene – Holocene, 24–0 Ma Pre๊ ๊ O S D C P T J K Pg N Clockwise from top left: Grey seal (Halichoerus grypus), Steller sea lion (Eumetopias jubatus), New Zealand fur seal (Arctocephalus forsteri), walrus ...
Animals were seen to develop into adults of widely differing body plan, often through similar stages, from the egg, but zoologists knew almost nothing about how embryonic development was controlled at the molecular level, and therefore equally little about how developmental processes had evolved. [9]
Macroevolution refers to evolution that occurs at or above the level of species, in particular speciation and extinction, whereas microevolution refers to smaller evolutionary changes within a species or population, in particular shifts in allele frequency and adaptation. [135] Macroevolution is the outcome of long periods of microevolution. [136]
The first stage in the evolution of life on earth is often hypothesized to be the RNA world in which short self-replicating RNA molecules proliferated before the evolution of DNA and proteins. By this hypothesis, life started when RNA chains began to self-replicate, initiating the three mechanisms of Darwinian selection: heritability, variation ...