Growing up a shy and unassuming member of a wealthy British family, he appeared, at least to his father, to be idle and directionless. But even as a child, Darwin expressed an interest in nature.
Favourable variations are ones that increase chances for survival and procreation. Those advantageous variations are preserved and multiplied from generation to generation at the expense of less-advantageous ones. This is the process known as natural selection.
The outcome of the process is an organism that is well adapted to its environmentand evolution often occurs as a consequence. Natural selection, then, can be defined as the differential reproduction of alternative hereditary variants, determined by the fact that some variants increase the likelihood that the organisms having them will survive and reproduce more successfully than will organisms carrying alternative variants.
Selection may occur as a result of differences in survival, in fertility, in rate of development, in mating success, or in any other aspect of the life cycle. All of these differences can be incorporated under the term differential reproduction because all result in natural selection to the extent that they affect the number of progeny an organism leaves.
Darwin maintained that competition for limited resources results in the survival of the most-effective competitors. Nevertheless, natural selection may occur not only as a result of competition but also as a result of some aspect of the physical environmentsuch as inclement weather.
Moreover, natural selection would occur even if all the members of a population died at the same age, simply because some of them would have produced more offspring than others.
Natural selection is quantified by a measure called Darwinian fitness or relative fitness. Fitness in this sense is the relative probability that a hereditary characteristic will be reproduced; that is, the degree of fitness is a measure of the reproductive efficiency of the characteristic.
Biological evolution is the process of change and diversification of living things over time, and it affects all aspects of their lives— morphology form and structurephysiologybehaviour, and ecology.
Underlying these changes are changes in the hereditary materials. Evolution can be seen as a two-step process.
First, hereditary variation takes place; second, selection is made of those genetic variants that will be passed on most effectively to the following generations. Hereditary variation also entails two mechanisms—the spontaneous mutation of one variant into another and the sexual process that recombines those variants see recombination to form a multitude of variations.
The variants that arise by mutation or recombination are not transmitted equally from one generation to another.
Some may appear more frequently because they are favourable to the organism; the frequency of others may be determined by accidents of chance, called genetic drift. The gene pool The gene pool is the sum total of all the genes and combinations of genes that occur in a population of organisms of the same species.
It can be described by citing the frequencies of the alternative genetic constitutions. Consider, for example, a particular gene which geneticists call a locussuch as the one determining the MN blood group s in humans. One form of the gene codes for the M blood group, while the other form codes for the N blood group; different forms of the same gene are called allele s.
The MN gene pool of a particular population is specified by giving the frequencies of the alleles M and N.Charles Darwin The Evolution of Evolutionary Theory at the hand of Charles Darwin himself.
Evolution Versions and The idea of evolution – that is, of biological change over time – did not originate with Darwin. eventually led him to formulate his theory of evolution by natural selection. Darwin's Theory of Evolution Charles Darwin proposed the theory of evolution to explain the origin, diversity and complexity of life.
I will will disprove evolution by showing that natural selection only explains small evolutionary changes, collectively known as microevolution. Darwin demurred: he was much more interested in producing a watertight case for evolution by natural selection than in gaining credit for a theory that could be easily dismissed.
Nonetheless he started working on a manuscript in May of Charles Darwin, in full Charles Robert Darwin, (born February 12, , Shrewsbury, Shropshire, England—died April 19, , Downe, Kent), English naturalist whose scientific theory of evolution by natural selection became the foundation of modern evolutionary studies.
But Wallace and Lamarck should not be forgotten; both have their place in the history of the evolutionary theory, and therefore, are important to the content of this blog. Here is a little summary: Charles Darwin, Alfred Wallace and Jean-Baptiste Lamarck.
n One Long Argument, Ernst Mayr (evolutionary biologist, and originator of the Biological Species Concept) summarizes Darwin's theories, and traces the history of their acceptance by the world scientific community.
In the Preface, he begins: A modern evolutionist turns to Darwin's work again and.