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Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
The human body is not built from a professionally engineered blue print but a system shaped over long periods of time by evolution with all kinds of trade-offs and imperfections. Understanding the evolution of the human body can help medical doctors better understand and treat various disorders.
Richard Lenski's classic E. coli long-term evolution experiment is an example of adaptation in a competitive environment, ("improvement in fitness" during "survival of the fittest"). [64] The probability of a beneficial mutation occurring on some member of the lineage to give improved fitness is slowed by the competition.
In biology, evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organization , from kingdoms to species , and individual organisms and molecules , such as DNA and proteins .
The bird and the bat wing are examples of convergent evolution. However, anatomical comparisons can be misleading, as not all anatomical similarities indicate a close relationship. Organisms that share similar environments will often develop similar physical features, a process known as convergent evolution .
The universal tetrapod characteristics of front limbs that bend backward at the elbow and hind limbs that bend forward at the knee can plausibly be traced to early tetrapods living in shallow water. [18] Panderichthys is a 90–130 cm (35–50 in) long fish from the Late Devonian period (380 Mya). It has a large tetrapod-like head.
The evidence on which scientific accounts of human evolution are based comes from many fields of natural science. The main source of knowledge about the evolutionary process has traditionally been the fossil record, but since the development of genetics beginning in the 1970s, DNA analysis has come to occupy a place of comparable importance.
Human evolution (origins of society and culture) – Transition of human species to anthropologically modern behavior; Inversion (evolutionary biology) – Hypothesis in developmental biology; Mosaic evolution – Evolution of characters at various rates both within and between species