Genetics and Evolution - Natural Selection, The Modern Evolution-creation Debate, Variation And Adaptation, Mutation, Modern Synthesis Ofevolutionary Genetics
change changes species time
The essence of Darwinism lies in a single phrase: natural selection is the creative force of evolutionary change. No one denies that selection will play a negative role in eliminating the unfit. Darwinian theories require that it create the fit as well.
—Stephen J. Gould
The term "evolution" has multiple meanings; it is most generally used to describe the theory that all organisms are linked via descent to a common ancestor. Evolution also refers to the gradual process during which change occurs. In biology it is the theory that groups of organisms, such as species, change or develop over long periods of time so that their descendants differ from their ancestors morphologically (in form, structure, and physiology) in terms of their life processes, activities, and functions. (Species are the smallest groups into which most living things that share common characteristics are divided. Among the key characteristics that define a species is that its members can breed within the group but not outside it.)
It is important to understand that not all change is considered evolution; evolution encompasses only those changes that are inheritable and may be passed on to the next generation. For example, evolution does not explain why humans are taller and bigger today than they were a century ago. This phenotypic (observable) change is attributable to changes in the environment—that is, improvements in nutrition and medicine—and is not inherited. Similarly, it should also be noted that while evolution leads to increasing complexity, it does not necessarily signify progress because an adaptation, trait, or strategy that is successful at one time may be unsuccessful at another.
In genetic terms, evolution can be defined as any change in the gene pool of a population over time or changes in the frequency of alleles in populations of organisms from generation to generation. Evolution requires genetic variation, and the incremental and often uneven changes described by the process of evolution arise in response to an organism's or species' genetic response to environmental influences.
Evidence of evolution has been derived from fossil records, genetics study, and changes observed among organisms over time. The process produces the transformations that generate new species only able to survive if they can respond quickly and favorably enough to environmental changes. Population genetics is the discipline that considers variation and changing ratios of genetic types within populations to explain how populations evolve. Such changes within a population are termed "microevolution." In contrast, "macroevolution" describes larger-scale changes that produce entirely new species. Although some researchers speculate that the two processes are different, many scientists believe that macroevolutionary change is simply the final outcome of the collected effects of microevolution.
Molecular evolution is the term used to describe the period before cellular life developed on Earth. Scientists speculate that specific chemical reactions occurred that created information-containing molecules that contributed to the origin of life on this planet. Theories about molecular evolution presume that these early information-containing molecules were precursors to genetic structures capable of replication (duplication of deoxyribonucleic acid [DNA] by copying specific nucleic acid sequences) and mutation (change in DNA sequence).
Additional Topics
Genetics and Evolution - Natural Selection
Natural selection is a mechanism of evolution. The principles of organic evolution by means of natural selection were described by the British naturalist Charles Darwin. Much of his early research focused on geology, and he developed theories about the origin of different land formations when he went on a five-year expedition around the world aboard the HMS Beagle. During his travels he developed…
Genetics and Evolution - The Modern Evolution-creation Debate
Arguments over the accuracy and importance of Darwin's theories have continued to the present day. Creationists believe the biblical account of the earth's creation as it appears in the book of Genesis. Some acknowledge "microevolution"—changes in a species over time in response to natural selection—but they generally do not believe in speciation—th…
Genetics and Evolution - Variation And Adaptation
Effective adaptations and variations are perpetuated in a species and tend to be incorporated into the normal or predominant phenotype for most individuals in the species. Variation persists, but it ranges around an evolutionarily determined norm. This is called adaptive radiation. For example, over time Darwin's finches have developed beaks best suited to their functions. The finches that …
Genetics and Evolution - Mutation
Variation is the essence of life, and mutations are the source of all genetic variation. A staggering number and variety of alterations, rearrangements, and duplications of genetic material have occurred since the first living cells, in which there is an incredible range of life forms, from single-celled amoebas and fruit flies to giant dinosaurs and humans. These dramatically different life forms…
Genetics and Evolution - Modern Synthesis Ofevolutionary Genetics
Present-day theories of evolutionary genetics are indebted to Darwin for his groundbreaking descriptions of organisms, individuals, and speciation. Modern theory differs considerably in that it addresses evolutionary mechanisms at the level of populations, genes, and phenotypes—and incorporates understanding of actions, such as genetic drift, that Darwin had not considered. The modern synth…
Genetics and Evolution - Theories About The Evolutionof Handedness
One characteristic that distinguishes humans from other primates is the fact that the overwhelming majority (90%) are right-handed. With the exception of parrots, which show a similar population bias for right-footedness, other animals appear to have more balanced proportions of hand or foot preferences. In "The Genetics and Evolution of Handedness" (Psychological Review, vol. 104, n…
Genetics and Evolution - The Role Of Genes Inexceptional Longevity
The number of centenarians (people 100 years or older) in the population is increasing by 8% per year, significantly more rapidly than the annual 1% increase in population. In the United States at the turn of the twentieth century about one in 100,000 people were centenarians; by 2002 the rate had risen to one in 10,000. This remarkable increase probably results from improved survival rates in ear…
Citing this material
Please include a link to this page if you have found this material useful for research or writing a related article. Content on this website is from high-quality, licensed material originally published in print form. You can always be sure you're reading unbiased, factual, and accurate information.
Highlight the text below, right-click, and select “copy”. Paste the link into your website, email, or any other HTML document.
User Comments
over 2 years ago
die
over 4 years ago
Packers and Movers in Delhi @
http://list5th.in/packers-and-movers-delhi/
Packers and Movers in Gurgaon @
http://list5th.in/packers-and-movers-gurgaon/
Packers and Movers in Noida @
http://list5th.in/packers-and-movers-noida/
Packers and Movers in Faridabad @
http://list5th.in/packers-and-movers-faridabad/
Packers and Movers in Ghaziabad @
http://list5th.in/packers-and-movers-ghaziabad/
Packers and Movers in India @
http://list5th.in/
over 4 years ago
Packers and Movers in Pune @
http://list5th.in/packers-and-movers-pune/
Packers and Movers in Mumbai @
http://list5th.in/packers-and-movers-mumbai/
Packers and Movers in Bangalore @
http://list5th.in/packers-and-movers-bangalore/
Packers and Movers in Hyderabad @
http://list5th.in/packers-and-movers-hyderabad/
Packers and Movers in Chennai @
http://list5th.in/packers-and-movers-chennai/
Packers and Movers in Delhi @
http://3th.co.in/packers-and-movers-delhi/