Chapter 20 Flashcards
A population is ___________________________ and a gene pool is ________________________.
a group of interbreeding organisms, the collection of genes and alleles found in a population
If a population is in Hardy-Weinberg equilibrium, the equation _______________ can be used to calculate genotype frequencies.
p^2 + 2pq + q^2 = 1
T or F: the highest expected frequency of the heterozygous genotype would be when p = q = 0.5, 2pq = 0.5.
True
T or F: two generations of random mating in a mixed population produces Hardy-Weinberg equilibrium frequencies for genotypes
False, only one generation
The six assumptions of HWE are….
(1) infinite population
(2) random mating occurs in the population
(3) no natural selection
(4) no migration (gene flow)
(5) no mutation
(6) no genetic drift
The four predictions of HWE are….
(1) allele frequencies remain stable over time
(2) allele distribution into genotypes is predictable
(3) stable equilibrium frequencies of alleles and genotypes are maintained
(4) evolutionary and nonrandom mating effects are predictable
When there are three alleles and you are calculating expected genotype frequencies, __________ = 1 and ________________________ = 1
(p + q + r)^2 = 1
p^2 + q^2 + r^2 + 2pq +2pr + 2qr = 1 - [6 possible genotypes]
What are the two methods for determining autosomal allele frequencies from genotype frequencies in diploids?
(1) Gene-counting Method: with codominance, the total amount of alleles is 2(number of people), allowing for allele frequencies to be calculated
(2) Square root Method: used with dominant-recessive alleles, HW equilibrium is assumed
There are three major sources of genetic variability and two population-environment interactions that contribute to evolution
Mutation, Mode of Reproduction, Gene Flow + Natural Selection, Genetic Drift
T or F: when estimating the number of survivors for each genotype to reproductive age, multiply the relative fitness (w) by the number of individuals. To estimate allele frequencies for the next generation, multiply number of survivors (B1B1) by 2 (alleles) and add the number of heterozygous (B1B2) alleles divided by the total survivor alleles.
True
In a model of natural selection favoring the heterozygous genotype, pE = _________ & qE = ________, where t = _______ & s = _______.
pE = t / ( s + t )
qE = s / ( s + t)
t = 1 - w (q^2)
s = 1 - w (p^2)
Mutation is…
the ultimate source of all new genetic variation in populations
Forward mutation rate VS Reverse mutation rate
the rate of creating new alleles, the rate of mutation to original allele
Gene Flow can…. (4 things)
(1) introduce new alleles
(2) increase frequency of existing alleles
(3) remove/reduce existing alleles
(4) create admixed population
The change in allele frequencies produced in an admixed population by gene flow from population 1 into population 2 can be described by __________________ of migration that depicts a one way process of gene flow from a mainland population to an island population.
the Island Model
Genetic Drift refers to
chance fluctuations of allele frequencies due to “sampling bias”
Genetic drift occurs in all populations but is especially prominent in _____ populations
small
T or F: in the absence of any other evolutionary influence and given a sufficient number of generations, allele frequencies will drift until ultimately one allele reaches fixation at a frequency of 1.0 and the other alleles are eliminated.
True
Inbreeding results in an increase of _________ genotypes.
homozygous
T or F: inbreeding changes allele frequencies while also systematically redistributing the alleles into genotypes that increase homozygosity, while reducing heterozygosity
False, the second portion is true though.
Inbreeding Depression
the reduction in fitness of inbred organisms, often due to reduced genetic heterozygosity.
Biological Species Concept (BSC)
the most widely used definition of a species - a group of organisms capable of interbreeding with each other but isolated from other species
4 Things wrong with BSC
(1) cannot be applied to fossils
(2) difficult to know if two organisms can reproduce or not
(3) cannot be applied to asexual organisms
(4) exception is interspecies hybridization (EX: mules)
Allopatric Speciation
populations diverge due to physical barrier, causing new species to develop in separate geographic locations
Sympatric Speciation
populations share a territory but are isolated by genetic, behavioral, seasonal, or ecosystem-based mechanisms that prevent gene flow
Hybrid Speciation
formation of a new species due to hybridization between existing species
List the Mechanisms of Reproductive Isolation
Big Gay Guys Hate My Teeth
Prezygotic Mechanisms
(1) Behavioral Isolation - incompatible sexual behavior
(2) Gametic Isolation - gametes fail to unite
(3) Geographic Isolation - separate geographic locations
(4) Habitat Isolation - species inhabit different ecosystems
(5) Mechanical Isolation - genitalia incompatible
(6) Temporal Isolation - timing of reproduction is different
Postzygotic Mechanisms
(1) Hybrid breakdown - fitness of progeny is worse
(2) Hybrid inviability - fertilized zygote fails to survive gestation
(3) Hybrid sterility - viable but infertile
T or F: a case study of Hawaiian Drosophila species demonstrates that new species diversify following colonization of new habitats. The oldest species are found on the oldest islands.
True