Chapter 25: Population and Evolutionary Genetics Flashcards
Population
group of individuals with a common set of genes that lives in the same geographic area and actively or potentially interbreeds
Gene Pool
all of the alleles present in a population
What do most populations contain a high degree of?
heterozygosity
Differential reproduction in a population leads to…
-changes in the allele and genotype frequencies in subsquent generations
-microevolution
Microevolution
changes in allele frequencies that do not result in reproductive isolation
What does the Hardy-Weinberg equation describe?
allele frequencies and genotype frequencies in populations
What is the simple mathmateical model that shows the relationship between proportions of alleles in the gene pool and the frequency of different genotypes?
Hardy-Weinberg
What are some assumptions made by Hardy-Weinberg?
-there is equal rate of survival and reproduction (no selection occurs)
-no new alleles arise or are created by mutation
-there is no migration into or out of the population
-the population is infintely large
-random mating occurs
what are predictions made by Hardy-Weinberg?
the frequency of alleles in the gene pool does not change over time
What are some consequences of Hardy-Weinberg?
-dominant traits do not necessarily increase from one generation to the next
-genetic variability can be maintained
-By knowing one genotype, frequencies of others can be calculated
What allows the frequency of heterozygotes to be measured?
Hardy-Weinberg
What may cause allele frequency to change from one generation to the next?
if individuals are subject to natural selection and do not have equal rates of survival and reproductive success
What is the principal force that shifts allele frequencies within large populations?
natural selection
What fashion do organisims tend to reproduce in in the Wallace-Darwin Concept of natural selection?
exponential fashion
Individuals in a species exhibit ____ in phenotype
variations
Are variations heritable?
many of them are
What is a trade off of exponential reproduction?
more offspring are produced than can survive. Struggle for survival
What do population and species change due to?
natural selection
Fitness
an individual’s genetic contribution to the next generation
What allows fitness to be examined for each genotype?
Hardy-Weinberg
What time frame does weak selection cause substantial changes in allele frequencies?
occurs over thousands of generations
What is the fitness of a homozygous recessive individual that dies before producing offspring
w=o
What causes rapid changes in allele frequencies?
large differences in genotypes
Mutation
only process that creates new alleles in a gene pool
Mutation rates
number of new mutant alleles per given number of gametes
What does mutation rates look at?
the extent to which mutation can cause allele frequencies to change from one generation to the next can be estimated
Migration
occurs when individuals move between populations
What is caused by migration?
allele frequencies in these new populations may differ over time
Genetic Drift
occurs when the number of reproducing individuals in a population is too small to ensure that all the alleles in the gene pool will be passed on to the next generation in their existing frequencies
What results from genetic drift?
may result in one allele becoming fixed and one allele becoming fixed and one allele disapperaring in a population, simply by chance
Population bottlenecks occur..
when a large population undergoes a drastic but temporary reduction in numbers
What is greatly reduced in a population bottleneck?
genetic diversity
Positive assortment mating
similar genotypes are more likely to mate than dissimilar ones
Negative assortive mating
in which dissimilar genotypes are more likely to mate than similar ones
Inbreeding
mating individuals are related
What does inbreeding increase in a population?
number of homozygotes (for a given allele)
What will a completely inbred population theoretically consist of?
all homozygotes
Species
group of actually or potentially interbreeding organisims that is reproductively isolated in nature from all other such groups
Speciation
transforms the gene pool of the parental species or divides a gene pool into two or more seperate and distinct gene pools
When can speciation occur?
can occur gradually or within a few generations
Macroevolution
genetic changes that result in reproductive isolation between or among populations and lead to the formation of new species
what is macroevolution?
microevolution+time
Microevolution
alleles change over measurable periods of time
Are new species made in microevolution?
no new species
What can be used to reconstruct evolutionary histories?
genetic differences among present day species
