Related topics: genes , birds , mutations , natural selection
Evolution
hideIn biology, evolution is change in the genetic material of a population of organisms from one generation to the next. Though changes produced in any one generation are small, differences accumulate with each generation and can, over time, cause substantial changes in the population, a process that can culminate in the emergence of new species. Indeed, the similarities amongst species suggest that all known species are descended from a common ancestor (or ancestral gene pool) through this process of gradual divergence .
The basis of evolution is the genes that are passed on from generation to generation; these produce an organism's inherited traits. These traits vary within populations, with organisms showing heritable differences (variation) in their traits. Evolution itself is the product of two opposing forces: processes that constantly introduce variation, and processes that make variants either become more common or rare. New variation arises in two main ways: either from mutations in genes, or from the transfer of genes between populations and between species. In species that reproduce sexually, new combinations of genes are also produced by genetic recombination, which can increase variation between organisms.
Two major mechanisms determine which variants will become more common or rare in a population. One is natural selection, a process that causes helpful traits (those that increase the chance of survival and reproduction) to become more common in a population and causes harmful traits to become more rare. This occurs because individuals with advantageous traits are more likely to reproduce, meaning that more individuals in the next generation will inherit these traits. Over many generations, adaptations occur through a combination of successive, small, random changes in traits, and natural selection of the variants best-suited for their environment. The other major mechanism driving evolution is genetic drift, an independent process that produces random changes in the frequency of traits in a population. Genetic drift results from the role that chance plays in whether a given trait will be passed on as individuals survive and reproduce.
Evolutionary biologists document the fact that evolution occurs, and also develop and test theories that explain its causes. The study of evolutionary biology began in the mid-nineteenth century, when studies of the fossil record and the diversity of living organisms convinced most scientists that species changed over time. However, the mechanism driving these changes remained unclear until the theories of natural selection were independently discovered by Charles Darwin and Alfred Wallace. Darwin's landmark work On the Origin of Species of 1859 brought the new theories of evolution by natural selection to a wide audience. Darwin's work soon led to overwhelming acceptance of evolution among scientists. In the 1930s, Darwinian natural selection was combined with Mendelian inheritance to form the modern evolutionary synthesis, which connected the units of evolution (genes) and the mechanism of evolution (natural selection). This powerful explanatory and predictive theory directs research by constantly raising new questions, and it has become the central organizing principle of modern biology, providing a unifying explanation for the diversity of life on Earth.
For more information about Evolution, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with evolution
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(PhysOrg.com) -- The first stars in the universe may have been very different from the stars we see today, yet they may hold clues to understanding some of the mysterious features of the universe. These "dark ...
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Oct 22, 2009 |
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(PhysOrg.com) -- For more than 50 years, physicists have been intrigued by the concept of closed time-like curves (CTCs). Because a CTC returns to its starting point, it raises the possibility of traveling backward in time. ...
How Did Evolution Begin?
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(PhysOrg.com) -- Life's ability to replicate itself is essential for evolution, yet even the simplest kind of replication requires a relatively complex system. So what kind of non-replicating system might ...
Robots Reveal Insights into Evolution
Sep 16, 2009 |
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(PhysOrg.com) -- In an ironic twist to our understanding of life, robots may offer a greater degree of realism for studying some of the intricacies of natural selection and evolution than real organisms offer. ...
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May 28, 2009 |
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(PhysOrg.com) -- “Axionlike particles are interesting because they come up regularly when scientists study string theory. By looking at their properties, you hope to learn about string theory, or some other unified theory ...
Mass Extinctions, Ancient Viruses May Hold Clues to Life’s Origins
Apr 03, 2009 |
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(PhysOrg.com) -- Mass extinctions occur repeatedly, though irregularly, throughout Earth’s history, and occasionally these extinctions have been devastating to life on our planet - or have they? Extinction ...
First molars provide insight into evolution of great apes, humans
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The timing of molar emergence and its relation to growth and reproduction in apes is being reported by two scientists at Arizona State University's Institute of Human Origins in the Dec. 28 online early edition of the Proceedings of ...
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Other Sciences / Social Sciences
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(PhysOrg.com) -- Researchers at the University of California, Berkeley, are challenging long-held beliefs that human beings are wired to be selfish. In a wide range of studies, social scientists are amassing ...
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Space & Earth / Earth Sciences
Nov 23, 2009 |
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A new study provides "incontrovertible evidence" that the volcanic super-eruption of Toba on the island of Sumatra about 73,000 years ago deforested much of central India, some 3,000 miles from the epicenter, ...
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(PhysOrg.com) -- Astrophysicists at the University of Warwick and Kiel University have discovered two earth sized bodies with oxygen rich atmospheres - however there is a bit of a disappointing snag for anyone ...
Why can't chimps speak? Study links evolution of single gene to human capacity for language
Nov 11, 2009 |
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(PhysOrg.com) -- If humans are genetically related to chimps, why did our brains develop the innate ability for language and speech while theirs did not?
Ancient penguin DNA raises doubts about accuracy of genetic dating techniques
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Penguins that died 44,000 years ago in Antarctica have provided extraordinary frozen DNA samples that challenge the accuracy of traditional genetic aging measurements, and suggest those approaches have been ...
Ancient 'Lucy' Species Ate A Different Diet Than Previously Thought
Other Sciences / Archaeology & Fossils
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(PhysOrg.com) -- Research examining microscopic marks on the teeth of the "Lucy" species Australopithecus afarensis suggests that the ancient hominid ate a different diet than the tooth enamel, size and sh ...
Are humans still evolving? Absolutely, says new analysis of long-term survey of human health
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Although advances in medical care have improved standards of living over time, humans aren't entirely sheltered from the forces of natural selection, a new study shows.
International scientists set boundaries for survival
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Human activities have already pushed the Earth system beyond three of the planet's biophysical thresholds, with consequences that are detrimental or even catastrophic for large parts of the world; six others ...
