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The result of four billion years of evolution is the diversity of life around us, with an estimated 1.75 million different species in existence today. [ 71 ] [ 72 ] Usually the process of speciation is slow, occurring over very long time spans; thus direct observations within human life-spans are rare.
The great apes (Hominidae) show some cognitive and empathic abilities. Chimpanzees can make tools and use them to acquire foods and for social displays; they have mildly complex hunting strategies requiring cooperation, influence and rank; they are status conscious, manipulative and capable of deception; they can learn to use symbols and understand aspects of human language including some ...
Tinbergen's four questions, named after 20th century biologist Nikolaas Tinbergen, are complementary categories of explanations for animal behaviour. These are also commonly referred to as levels of analysis. [1] It suggests that an integrative understanding of behaviour must include ultimate (evolutionary) explanations, in particular:
Explanation of current form in terms of a historical sequence. Current Form. Explanation of the current form of species. How vs. Why Questions: Proximate. How an individual organism's structures function Ontogeny. Developmental explanations for changes in individuals, from DNA to their current form Mechanism
Evolution holds that all species are related and gradually change over generations. [1] In a population, the genetic variations affect the phenotypes (physical characteristics) of an organism. These changes in the phenotypes will be an advantage to some organisms, which will then be passed on to their offspring .
Mosaic evolution – Evolution of characters at various rates both within and between species; Parallel evolution – Similar evolution in distinct species; Quantum evolution – Evolution where transitional forms are particularly unstable and do not last long; Recurrent evolution – The repeated evolution of a particular character
A study of four mammalian genera: Hyopsodus, Pelycodus, Haplomylus (three from the Eocene), and Plesiadapis (from the Paleocene) found that—through a large number of stratigraphic layers and specimen sampling—each group exhibited, "gradual phyletic evolution, overall size increase, iterative evolution of small species, and character ...
As the gaps in the fossil record had been used as an argument against Darwin's gradualist evolution, de Beer's explanation supported the Darwinian position. [23] However, despite de Beer, the modern synthesis largely ignored embryonic development to explain the form of organisms, since population genetics appeared to be an adequate explanation ...