Variation is maintained in some ways by having two alleles determine the singular phenotypic expression. Geographical separation between populations produces more variation by evolving to different environment. Mutations give population’s new alleles to work with and sexual recombination and fertilization is also accountable for genetic variation.
What is the Hardy- Weinberg equation/ assumptions and how is it used?
P+Q=1 P^2+ 2pq + q^2=1 P= % of dominant allele q= % of recessive alleles P^2= homo-dominant 2pq=heterozygous q^2= homo-recessive. Assumes that these ratios will remain the same so long as the population meets the following criteria: 1. Large population (no genetic drift) 2, Isolation (no gene flow) 3. No net mutations 4. Random mating (no sexual selection) 5. No natural selection. This is used to measure the rate at which a population is evolving because if it defies these criteria the ratios will be changing and therefore we can deduce that it is evolving.
What are the different mechanisms for evolution?
Natural selection- where certain characteristics that benefit an organisms in relation to their environment increase in frequency because of their higher survival rate.
Genetic Drift- Allele frequencies change at random based on a smaller population either most of it dying out or a small group being separated from the rest
Gene Flow- The movement of certain alleles in or out of a population because certain organisms with their gamete move in or out. In plants this can happen merely from the wind blowing
Facts:
- Genetic drift can occur in one of two ways bottleneck effect (natural disaster kills off most the population or founders effect (small group within the population gets separated from the whole)
- Natural selection is the only evolutionary mechanism that makes an organism more suited to their environment
- Balancing selection is when two variations of genotype are maintained through selection
- Neutral variation occurs when mutations cause neither a positive or negative effect
- Sexual selection often encourages phenotypes that have nothing to do with the organisms ability to survive in their environment.
Directional selection is when the environment favors the extreme of a characteristic so the trend moves towards the extreme. Disruptive is when the environment favors both extremes so the trend moves away from the average in both directions. Stabilizing selection is when the average makes for more successful organisms so the trend moves towards the average and away from both extremes.
Summary: Genetic variation is rampant there is variation within a population, between populations, between the organisms in different geographical locations ect. Mutations introduce new alleles into a population but the most genetic variation within a population comes from crossing over, independent assortment, and fertilization. Populations of species have a gene pool, which is the combination of all their alleles when the frequencies of these alleles are changing evolution is occurring. The hardy-Weinberg principle assumes that allele frequency is remaining the same and is used to compare to the actual and measure evolution rates. Allele frequencies are changed by: natural selection, genetic drift, and gene flow. Natural selection is the only change in a allele frequency that is guaranteed to improve the population, however it will never make the perfect organism because it has to work with the variation already present it doesn’t create new characteristics.
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