The types of organisms living on Earth have changed significantly over time due to various factors. What important event occurre
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1) <u><em>Natural Selection- General speaking, something must cause differential reproduction and then better suited individuals will survive over time.</em></u>
<u><em>- Detailed Explanation -</em></u>
<u><em>Natural selection is the process in which individuals whom are better suited to their environment will have an increase in fitness. It occurs over multiple generations and can take a very long period of time to occur. </em></u>
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<u><em>For natural selection to occur, the following must be true: </em></u>
<u><em>1. There must be variation in traits (every individual can't be identical) </em></u>
<u><em>2. There must be differential reproduction (some individuals are more likely to reproduce than others) </em></u>
<u><em>3. Traits are passed on from generation to generation </em></u>
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<u><em>Thus, the first step in natural selection is that something must cause differential reproduction. This could be the introduction of a predator, a disease, a random mutation that is detrimental, a change in resource availability such as a drought, and so forth. </em></u>
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<u><em>This image shows how a genetic mutation is unfavorable and is selected against, but the same process holds for a gene that is unfavorable during any scenario.</em></u>
<u><em>This event causes some individuals to survive and reproduce and some to be less successful. For example, a predator is introduced and it hunts and kills mostly individuals with shorter legs that run slowly. Or the environment undergoes a long drought and individuals in the species who have a gene that helps them perspire (sweat) less are more successful. </em></u>
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<u><em>Over multiple generations, the genetic composition of the species changes. Maybe within six generations the predator has completely wiped out individuals with shorter legs. Maybe within two generations the drought completely eliminates individuals with a gene that results in excess perspiration. The amount of time will vary.</em></u>
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<u><em>2) Mutation - A change in the genetic structure of an organism.</em></u>
<u><em>Explanation:</em></u>
<u><em>Usually, a mutation has to be expressed as some macro-functional characteristic although some may be hidden in internal systems.</em></u>
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<u><em>3) Genetic Drift- Genetic drift is the change in the frequency of an existing allele in a population due to random sampling of organisms.</em></u>
<u><em>Explanation:</em></u>
<u><em>The effect of genetic drift is larger when there are few copies of an allele, whereas when there are many copies the effect is smaller. </em></u>
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<u><em>Genetic drift describes random fluctuations in the number of gene variants in a population. Once it begins, genetic drift will continue until the involved allele is either lost by a population or until it is the only allele present in a population at a particular locus. Both possibilities reduce the genetic diversity of a population. </em></u>
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<u><em>Genetic drift can cause a new population to be genetically distinct from its original population, which has led to the hypothesis that it plays a role in the evolution of new species.</em></u>
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<u><em>4) Gene Flow- Gene flow is a concept in population genetics to refer to the movement of genes or alleles between interbreeding populations of a particular species.</em></u>
<u><em>Explanation:</em></u>
<u><em>Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants into and out of a population may result in a change in allele frequencies, thus changing the distribution of genetic diversity within the populations. High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. </em></u>
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<u><em>It is thought that gene flow constrains speciation by combining the gene pools of the groups and thus, prevents the development of differences in genetic variations that would have led to full speciation. It is expected to be lower in species that have low dispersal or mobility, occur in fragmented habitats, there is a long distance between populations, and smaller population sizes. </em></u>
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<u><em>It includes different kinds of events, such as pollen being blown to a new destination or people moving to new cities or countries. However, there are certain factors that serve as barriers to gene flow. Some of the factors affecting the rate of gene flow include physical barriers, geological events and geographical barriers.</em></u>
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<u><em>5)Non Random mating- The nonrandom mating is a selective pattern.</em></u>
<u><em>Explanation:</em></u>
<u><em>The nonrandom pattern of mating is an assortative pattern of sexual reproduction. During the reproduction, similar phenotypes are selected for mating. It is a random process. It is also known as positive assortative mating. </em></u>
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The medial indentation on the kidney called hilum....
hope it's help ;)
