Facts Of Evolution

In biology, evolution is the change in the inherited traits of a population of organisms through successive generations. When a population splits into smaller groups, these groups evolve independently and develop into new species.

Anatomical similarities, geographical distribution of similar species and the fossil record indicate that all organisms are descended from a common ancestor through a long series of these divergence events, stretching back in a tree of life that has grown over the 3,500 million years of life on Earth.

Evolution is the product of two opposing forces: processes that constantly introduce variation in traits, and processes that make particular variants become more common or rare. A trait is a particular characteristic such as eye color, height, or a behavior that is expressed when an organism's genes interact with its environment.

Genes vary within populations, so organisms show heritable differences (variation) in their traits. The main cause of variation is mutation, which changes the sequence of a gene. Altered genes are then inherited by offspring. There can sometimes also be transfer of genes between species.

Two main processes cause variants to become more common or rare in a population. One is natural selection, which causes traits that aid survival and reproduction to become more common, and traits that hinder survival and reproduction to become more rare.

Natural selection occurs because only a few individuals in each generation will survive, since resources are limited and organisms produce many more offspring than their environment can support.

Over many generations mutations produce successive, small, random changes in traits, which are then filtered by natural selection and the beneficial changes retained. This adjusts traits so they become suited to an organism's environment: these adjustments are called adaptations.

Not every trait, however, is an adaptation. Another cause of evolution is genetic drift, an independent process that produces entirely random changes in how common traits are in a population. Genetic drift comes from the role that chance plays in whether a trait will be passed on to the next generation.

• http://en.wikipedia.org/wiki/Evolution
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How Fast Is Evolution?

Rates of Evolution

Evolutionary rates can be measured quantitatively for a character within a lineage, and we begin by seeing how this is conventionally done. We then look at a large compilation of over 500 such measurements and ask whether fossil evolutionary rates fit in with the theory of population genetics.

Punctuated equilibrium is an influential modern idea about evolutionary rates in fossils and we discuss the theory, how to test it, evidence for and against it, and its conceptual relation with the modern synthesis.

The rate of evolution is a measurement of the change in an evolutionary lineage over time.

The method for measuring the rate of evolution can be illustrated by work done by MacFadden on horse teeth: horse teeth are classic materials in the study of evolution.

The rate of evolution is measured as follows:

Suppose that a character has been measured at two times, t1 and t2 ; t1 and t2 are expressed as times before the present in millions of years.

The time interval between the two samples can be written as:Dt = t1 - t2,

which is 1 million years if t1 = 15.2 and t2 =14.2 The average value of the character is defined as x1 in the earlier sample and x2 in the later sample; we then take natural logarithms of x1 and x2 (the natural logarithm is the log to base e where e = 2.718, and it is symbolized by ln).

The evolutionary rate (r) then is

r = (ln(x2) - ln(x1)) / Dt

The rate of evolution is measured in 'darwins'.

Haldane defined a 'darwin' as a unit to measure evolutionary rates; one darwin is a change in the character by a factor of e in one million years.

The formula above for r gives the rate in darwins provided that the time interval is in millions of years.

• http://www.blackwellpublishing.com/ri...
• http://en.wikipedia.org/wiki/Darwin_%...
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Evolution is Real by standup4REALscience

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Five videos to prove that the theory of evolution isn't fake pseudo-science like intelligent design is.