Ancient Greek Views Evolution is not so much a modern discovery as some of its advocates would have us believe.
Genetic diversity and Population genetics An individual organism's phenotype results from both its genotype and the influence from the environment it has lived in.
A substantial part of the phenotypic variation in a population is caused by genotypic variation. The frequency of one particular allele will become more or less prevalent relative to other forms of that gene. Variation disappears when a new allele reaches the point of fixation —when it either disappears from the population or replaces the ancestral allele entirely.
Before the discovery of Mendelian genetics, one common hypothesis was blending inheritance.
But with blending inheritance, genetic variance would be rapidly lost, making evolution by natural selection implausible. The Hardy—Weinberg principle provides the solution to how variation is maintained in a population with Mendelian inheritance.
The frequencies of alleles variations in a gene will remain constant in the absence of selection, mutation, migration and genetic drift.
Despite the constant introduction of new variation through mutation and gene flow, most of the genome of a species is identical in all individuals of that species. Mutation Duplication of part of a chromosome Mutations are changes in the DNA sequence of a cell's genome.
When mutations occur, they may alter the product of a geneor prevent the gene from functioning, or have no effect. This process is easier once a gene has been duplicated because it increases the redundancy of the system; one gene in the pair can acquire a new function while the other copy continues to perform its original function.
Sexual reproductionGenetic recombinationand Evolution of sexual reproduction In asexual organisms, genes are inherited together, or linked, as they cannot mix with genes of other organisms during reproduction.
In contrast, the offspring of sexual organisms contain random mixtures of their parents' chromosomes that are produced through independent assortment. In a related process called homologous recombinationsexual organisms exchange DNA between two matching chromosomes.
If each individual were to contribute to the same number of offspring twoa the sexual population remains the same size each generation, where the b Asexual reproduction population doubles in size each generation. The two-fold cost of sex was first described by John Maynard Smith.
This cost does not apply to hermaphroditic species, like most plants and many invertebrates. The Red Queen hypothesis has been used to explain the significance of sexual reproduction as a means to enable continual evolution and adaptation in response to coevolution with other species in an ever-changing environment.
Gene flow Gene flow is the exchange of genes between populations and between species. Gene flow can be caused by the movement of individuals between separate populations of organisms, as might be caused by the movement of mice between inland and coastal populations, or the movement of pollen between heavy-metal-tolerant and heavy-metal-sensitive populations of grasses.
Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer. Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria. It is possible that eukaryotes themselves originated from horizontal gene transfers between bacteria and archaea.
From a neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms,  for example, the allele for black colour in a population of moths becoming more common.
Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, genetic hitchhiking, mutation and gene flow.Significant Energy E vents in Earth's and Life's History as of Energy Event.
1 What Is The In ternet (And What Makes It Work) - December, By Robert E. Kahn and Vinton G. Cerf In this issue: INTRODUCTION THE EVOLUTION OF THE INTERNET. The word "evolution" in its broadest sense refers to change or growth that occurs in a particular order. Although this broad version of the term would include astronomical evolution and the evolution of computer design, this article focuses on the evolution of biological organisms. That use of the. I remain the official Senior Maverick for Wired, a magazine I helped co-found 25 years ago. I do one article for Wired per year. My most recent published writings are listed here, in chronological order. My newest book, The Inevitable, a New York Times bestseller, is now available in paperback. The.
Timeframe. Significance. Nuclear fusion begins in the Sun. c. billion years ago (“bya”) Provides the power for all of Earth's geophysical, geochemical, and ecological systems, with . Cultural evolution: Cultural evolution, the development of one or more cultures from simpler to more complex forms.
The subject may be viewed as a unilinear phenomenon that describes the evolution of human behaviour as a whole, or it may be viewed as a multilinear phenomenon, in which case it describes the evolution.
Jean-Jacques Rousseau was one of the most influential thinkers during the Enlightenment in eighteenth century Europe.
His first major philosophical work, A Discourse on the Sciences and Arts, was the winning response to an essay contest conducted by the Academy of Dijon in In this work.
I remain the official Senior Maverick for Wired, a magazine I helped co-found 25 years ago. I do one article for Wired per year. My most recent published writings are listed here, in chronological order. My newest book, The Inevitable, a New York Times bestseller, is now available in paperback.
The. The Overview Effect: Space Exploration and Human Evolution (Library of Flight) [Frank White] on timberdesignmag.com *FREE* shipping on qualifying offers. The Overview Effect is an important book in helping people see that your attitude does change when you see the Earth from the space perspective - an experience that seems to be an almost universal phenomenon.
Evolution, theory in biology postulating that the various types of plants, animals, and other living things on Earth have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations.
The theory of evolution is one of the fundamental keystones of modern biological theory.. The diversity of the living world .