Whats a good summary for Darwin's theory of natural selection as the mechanism for evolution...???

Question

someone please I hate bio, help me :)

Answer 1

Natural selection is the evolutionary process by which favorable traits that are heritable become more common in successive generations of a population of reproducing organisms, and unfavorable traits that are heritable become less common. Natural selection acts on the phenotype, or the observable characteristics of an organism, such that individuals with favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes. If these phenotypes have a genetic basis, then the genotype associated with the favorable phenotype will increase in frequency in the next generation. Over time, this passive process can result in adaptations that enable organisms to be highly specialized for life in a particular ecological niche, and in speciation events in which new species emerge.

Natural selection is one of the cornerstones of modern biology. The term was introduced by Charles Darwin in his groundbreaking 1859 book The Origin of Species,[1] by analogy with artificial selection, a process by which individuals with traits considered desirable by human breeders are systematically favored for reproduction. The concept of natural selection was originally developed in the absence of a theory of inheritance; the union of traditional Darwinian evolution with subsequent discoveries in molecular genetics is termed the modern evolutionary synthesis. Although other mechanisms of molecular evolution, such as the neutral theory advanced by Motoo Kimura, have been identified as important causes of genetic diversity, natural selection remains the single primary explanation for adaptive evolution.

Answer 2

volution
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This article is about evolution in biology. For other uses, see Evolution (disambiguation).

For a non-technical introduction to the topic, please see Introduction to evolution.

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In biology, evolution is the change in the inherited characteristics, or traits of a population of organisms. Heritable traits are encoded in the genetic material of an organism (usually DNA); changes in this genetic material (mutation) and the subsequent spread of these changes in the population drives evolution.

Natural selection, one of the processes that determines whether changes spread within the population, is a result of the advantage conferred on organisms with beneficial traits. If these traits increase the evolutionary fitness of an organism, they will be more likely to survive and reproduce than other organisms in the population. In doing so, they pass more copies of those heritable traits on to the next generation, causing advantageous traits becoming more common in each generation; the corresponding decrease in fitness for deleterious traits results in their become rarer.[1][2][3]

This simple process has a powerful effect, namely, adaptation: the gradual accumulation of new beneficial traits and the preservation of existing ones results in a population of organisms becoming better suited to its environment and ecological niche.[4]

Though natural selection is decidedly non-random in its manner of action, other more capricious forces have a strong hand in the process of evolution. Genetic drift results in heritable traits becoming more or less common simply due to random chance, as a result of sampling error.[citation needed] This aimless process has a profound influence, and in some instances may overwhelm the effects of natural selection - even a horse with favored odds can lose.

Differences in environment and the element of chance in what mutations happen to arise and which ones survive can cause different populations (or parts of populations) to develop in divergent directions. Enough divergence between two populations can eventually cause speciation, the emergence of two distinct types of organisms from a common origin. All known species are descended from a single ancestor through this process of divergence.[1][5][6]

Answer 3

HI,
Darwin's theory of evolution by natural selection

Natural Selection

* Populations show variation for almost all traits.
* Certain variations improve survivorship and the number of offspring left (improve fitness ).
* If these variations are heritable, their frequency increases each generation.
* These three steps are often called Survival of the Fittest.

Darwin's mechanism of evolution

* Modification occurs by natural selection.
* Hence, Darwin's theory is called the theory of evolution by natural selection.

Key figures influencing Darwin

* Erasmus Darwin
* Hutton and Lyell
* Malthus

Thomas Malthus

* In 1798 wrote Essay on the Principles of Population
* Populations tend to outgrow their resources, thus strong competition among individuals is expected.

Lyell and Hutton

* Charles Lyell's Principles of Geology (1830) was read by Darwin during the voyage of the Beagle .
* Lyell's expanded upon Hutton's notion of Uniformitarianism.
* Processes shaping the Earth today are the same as those that have shaped it in the past.
* Evidence that the earth was very old.

Wallace and Darwin

* It took Darwin 20-25 years to come up with his theory.
* Alfred Russell Wallace (during a two-week bout with malaria) independently came up with the same theory
* Both Wallace and Darwin presented joint papers on natural selection on 1 July 1858 at the Linnean Society of London.
* in 1859 Darwin published the first edition of The Origin of Species by Means of Natural Selection

Examples of the explanatory powers of Darwin's theory

* Drug resistance in bacteria.
* Pesticide resistance in insects.
* Sickle cell anemia
* Rabbits and myxomatosis.
* Industrial melanism

Sickle cell anemia and malaria --- how can something bad be good?

* Sickle-cell allele (S ) is a defect in the beta hemoglobin chain resulting from a single animo acid change.

* hemoglobins have two pairs of chains , alpha and beta
o Sickle allele, S, is a change in the beta chain (146 aa)
o glutamic acid at position 6 in normal beta replaced by valine
* S S homozygotes die, yet the sickle-cell allele is widespread throughout the world

* Key: the sickle-cell heterozygote is resistant to malaria
o The frequency of the S allele closely matches the world-wide distribution of malaria.

Rabbits and myxomatosis

* In 1859, 12 cute and cuddly rabbits brought to Australia.
* by 1886, the army of rabbits was advancing at over 66 miles a year, smashing through Òrabbit-proofÓ barriers. They spanned Australia by 1907.
* Myxomatosis introduced in 1950, with an initial mortality rate of 99.9%
* Mortality rate today is about 40%

The peppered moth and industrial melanism

* Dark (melanic) forms of the peppered moth increased in frequency in Southern England as air pollution (soot) darkened trees.
* As pollution controls were put in place, the light form of the moth increased in frequency.

Answer 4

the best summary....
Survival of the fittest!! :D