Evolution And Genetic Variation Essay

569 words - 3 pages

Review - For natural selection to occur individuals in a population must vary from one another. The variations may be visible (Eye color) or on the molecular level (Blood type). Only those traits that can be inherited are relevant to natural selection.
Where does genetic variation come from?
1. Genetic variation is random and caused by mutation. Random changes in a gene can result in a new allele. This new allele may be helpful or detrimental.
2. Sexual reproduction results in a unique combination of alleles that each individual inherits. Unique genetic combinations are the result of independent assortment in meiosis, random fertilization and crossing over
Genetic variation is caused by random processes but natural selection is not random!!!

Mechanisms of Evolution
Evolution is a change in a population’s genetic makeup from generation to generation. What causes a gene pool to change over time?
1. ...view middle of the document...

Secondary sex characteristics may be used to compete with members of the same sex. Examples: Physical combat or ritualized displays. One sex may be choosy in selecting their mates. Peacock tail sexually selected. Sexual selection often accounts for male/female differences in many animal species. There is some evidence that sexual selection accounts for differences in human male/female body size.

Tendency of organism to choose mate that resemble self is assortative mating. People tend to mate assortatively by height (i.e., tall women marry tall men) and skin color. Positive assortative mating tends to exaggerate differences between groups/populations.

3 Results of Natural Selection. Imagine a population of mice with a range of fur colors. If natural selection favors certain colors over others, there are 3 possible outcomes.
a. Directional selection - Shifts the make-up of a population in favor of one extreme. Example: drug resistant bacteria
b. Disruptive selection - Results in a balance between 2 or more contrasting phenotypes in a population.
c. Stabilizing selection - Favors intermediate phenotypes, getting rid of extremes. Usually prevails – resists changes in a well-adapted population.

2. Genetic drift
If a new generation gets its alleles from a large population, the new generation will represent the gene pool of the previous generation. However, the gene pool of a small population may not accurately represent the next generation because of sampling error (chance). This type of change in the gene pool (due to chance) is called genetic drift.

How do populations get so small that genetic drift occurs?
Bottleneck Effect - Natural disaster kills large numbers of the population, resulting in a smaller population that has different frequencies of alleles. By chance some alleles are more represented than others.

Founder effect - A few individuals leave the main population and colonize a new habitat. This smaller colony has a different genetic makeup than the main population. Smaller population is subject to genetic drift until it is large.

3. Gene flow
When fertile individuals move into or out of a population, causing a change in the allele frequency.

Other Papers Like Evolution And Genetic Variation

Transgenesis and Selective Breeding Essay

1529 words - 7 pages survival and health of sheep (2). In long term effects, Selective breeding has major impact on genetic biodiversity and the evolution of organisms by eliminating alternate alleles. As same desirable genotype for favorable traits are continually selected to bred by scientists and it is likely to remove the genes that are not purposely selected due to their insignificance, it not only has the risk of inbreeding depression, which decreases the ability

The Living Cell Biology Essay

549 words - 3 pages . Look at the scientific theory of evolution. Are we really descendents of apes? From a scientific perspective this is conceivable. The outbreak of Malaria is tolerated in most countries, but in Africa it is a widespread pandemic. This is an example of genetic variation. I believe 100 percent of us are genetic. We are created through genetic variation and the inheritance of variation. Natural selection is how we can cope with environmental changes

Henry the Viii

1444 words - 6 pages . insertion of that gene into the DNA of another organism * Recall examples of genetic modification in different cell types. 6.2 Stem cells: * understand that embryonic stem cells can give rise to any cell type * understand cells lose this ability as an animal matures * recall that there are embryonic and adult stem cells 7. Variation 7.1 Natural selection and evolution: * understand the sequence as: (1)variation (2

Amphidromous Fish Demographic Pattern

1452 words - 6 pages . After further analyzing, calculations were made and results were produced. (Arsal Khan) In order to assess the level of intraspecific variation in Si. zosterophorum and whether or not the two sample groups from this population are cryptic species, the genetic distance between the two subset populations was compared with the genetic distance between two congeneric species (Smilosicyopus fehlmanni and Smilosicyopus chloe) with overlapping habitats

Biology Final Studyguide

928 words - 4 pages selection? 48. What does Darwin’s theory of evolution suggest? 49. What main idea is Darwin’s theory of evolution based on? 50. What evidence for evolution was not available in Darwin’s time? 51. What is ‘fitness?’ 52. What is ‘variation?’ 53. What is ‘adaptation?’ 54. What is a gene pool? 55. What is temporal isolation? Geographic isolation? Behavioral isolation? 56. What are two sources of genetic variation? 57

Life as We Know It

1544 words - 7 pages Life as we Know it In 1859, Charles R. Darwin published his scientific theory with compelling evidence of a pattern in evolution known as natural selection, in his book The Origin of Species by Means of Natural Selection (Charles R. Darwin 5). Darwin’s theory of Evolution held concepts that all life is related and descended from a common ancestor; that over time, genetic mutation aided life forms in surviving. Although, along with Darwin’s

Hox Gene and Cambrian Explosion

4945 words - 20 pages questions 3-6,  questions 14 and 15. For students who wish to go further, particularly from a historical perspective, we suggest the following sites: 5. For many of the historical figures in our exploration of evolution, winkipedia does a reasonable job. 6. http://www.aboutdarwin.com/.  Obvious about whom this site is directed. 7. http://wallacefund.info/.  Also self-evident. Session 1.5: Genetic Drift, Sexual Selection

Darwin’s Theory of Natural Selection

1141 words - 5 pages selection. • Individuals do not evolve. "Evolution refers to generation-to-generation changes in population” (Simon, Reece, Dickey, p. 253) • Traits that are heritable can amplify or diminish through natural selection. • Evolution does not lead to perfectly adapted organisms because it is not goal directed. The larger changes that made due to natural selection that cause evolution occur because of genetic drift, gene flow, and mutations

Outline of How Life Works:

2617 words - 11 pages time, or evolution. Variation can be genetic or environmental. The ultimate source of genetic variation is mutation. Environmental variation: how the environment has affected an organism. For example, apples on a tree are exposed to different environmental factors (sunlight, shade, insects). Genetic variation: differences in individual DNA, leading to differences in that individual’s RNA and proteins and

Evolution Versus Creationism

2269 words - 10 pages genetic mutations (that they can actually help a species to survive better), arguing that genetic mutations do not help a species survive but rather handicap it. (Ruse, Michael) While this is just a small snap shot of everything that has been discovered and theorized in evolution and creationism, the discussions above provide strong argument as to why a growing number of people believe that the theory of evolution accurately explains how the

Science of Eugenics

626 words - 3 pages policies that countries enacted included segregation, birth control, genetic screening and marriage restrictions. These policies aimed at encouraging reproduction among the genetically advantaged and negative elimination through sterilization. Eugenics policies were first implemented in the early 1900 in the United States. It has roots in France, Germany, Great Britain and the United States. The scientific standing eugenics started to decay when

Related Essays

Garbology Essay

638 words - 3 pages within the purview of both, depending on forces that are thought to drive it. The evolutionary biology, paleontology, genomic phylostratigraphy, and comparative genomics contribute the most evidence for the processes and patterns, which can be classified as Macroevolution. A good example of this phenomenon is feathers appearance during birth evolution from theropod dinosaurs. Genetic variation is a phenomenon that is related to

The Research Of Robot Path Planning System

981 words - 4 pages encoding Set of the actual path Evolution Path adaptability evaluation Simulated annealing process Local optimal path Optimal path Path coding Path set Path copy Path cross Path variation Path encoding Set of the actual path Evolution Path adaptability evaluation Simulated annealing process Local optimal path Optimal path The entire genetic simulated annealing algorithm for path planning process shown in Figure 1: Figure 1

This Essay Is About Evolution, How Why And When

1067 words - 5 pages cousins, aunts, and uncles, because they share with them one or more common ancestors, such as a grandparent, or great-grandparent. But those cousins, aunts, and uncles are not their ancestors. In the same way, humans and other living primates are related, but none of these living relatives is a human ancestor.Is evolution a random process?Evolution is not a random process. The genetic variation on which natural selection acts may occur randomly

What Is Evolution? What Species Orginate From Evolution And What Species Have Remained The Same?

1650 words - 7 pages species theory. There cannot be evolution without genetic variation in the first place. Evolutionists cite the peppered moth more than any other single item--as evidence that "natural selection" can produce a change of one species to another. (Asimov 1990) These contrasting examples show numbers of variation is in proportion with the necessity of life. So there must be mutation and often recombination to generate the different genotypes or the