population genetics

Explain the statement "It is the population, not the individual, that evolves."
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Explain the statement "It is the population, not the individual, that evolves."
means that a single organism cannot evolve by itself. Natural selection is survival of the fittest, so the adaptations are relative to each other.
population
A group of individuals that belong to the same species and live in the same geographic area
species
A group whose members possess similar anatomical characteristics and have the ability to interbreed fertile offspring
gene pool
Combined genetic information of all the members of a particular population
List the five conditions that must be met for a population to remain in Hardy-Weinberg equilibrium.
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.
Explain why the majority of point mutations are harmless.
The majority of point mutations are harmless because there are several arrangements that can code for one amino acid. For example, UCU and UCC both code for serine, so a point mutation changing the U into a C would be completely harmless.
Explain how sexual recombination generates genetic variability.
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.
Explain the role of population size in genetic drift.
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.
Distinguish between the bottleneck effect and the founder effect.
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.
Describe how gene flow can act to reduce genetic differences between adjacent populations.
Gene flow can act to reduce genetic differences in adjacent populations because gene flow increases the movement of genes from different populations of species. The more interbreeding between two populations, the more similar their genes.
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.