population genetics

Explain the statement "It is the population, not the individual, that evolves."
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Condition 1 -> Very large population size. In a population of finite size, especially if that size is small, genetic drift can cause genotype frequencies to change over time.Condition 2 -> No migration. Gene flow due to the movement of individuals or gametes can increase the frequency of any genotype that is in high frequency among the immigrants.Condition 3 -> No net mutations. By changing one allele into another, mutations alter the gene pool.Condition 4 -> Random mating. If individuals pick mates with certain genotypes, then the random mating required for Hardy-Weinberg equilibrium does not occur.Condition 5 -> No natural selection. Differential survival and reproductive success of genotypes will alter their frequencies and may cause a detectable deviation from frequencies predicted by the Hardy-Weinberg equation.
Sexual recombination means that half of one parent's genes are combined with half of the other parent's genes in the offspring, which results in gene combination that did not previously exist. Sexual recombination and mutations would increase the amount of variation within a group. With sexual recombination, you constantly generate new variations in the population. If it weren't for this, all offspring would be identical to their parents and the only way for diversity to develop would be through mutations.
Genetic drift is the process of change in the genetic composition of a population due to chance or random events rather than by natural selection, resulting in changes in allele frequencies over time. If a population is small, there is is less variation between the organisms. If a catastrophe occurs, the population will not be able to recover as quickly because the alleles will not be as diverse.
Bottleneck effect -> Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.
Founder Effect -> Genetic drift attributable to colonization by a limited number of individuals from a larger population.
Distinguish among directional, disruptive, and stabilizing selection. Give an example of each mode of selection.Directional selection -> Natural selection that favors individuals at one end of the phenotypic range.Disruptive selection -> Natural selection that favors individuals at either extreme end of the phenotypic range.Stabilizing selection -> Natural selection that favors intermediate variants by acting against intermediate phenotypes.Explain how diploidy can protect a rare recessive allele from elimination by natural selection.Diploidy maintains genetic variation in the form of hidden recessive alleles because the cell has two sets of the recessive allele.Describe how heterozygote advantage and frequency-dependent selection promote balanced polymorphism.Heterozygote advantage occurs when heterozygotes have a higher fitness than do both homozygotes. In frequency-dependant selection, the fitness of a phenotype declines it it becomes too common in the population.