Chapter 20

Question 1

A population is ___________________________ and a gene pool is ________________________.

Answer 1

a group of interbreeding organisms, the collection of genes and alleles found in a population

Question 2

If a population is in Hardy-Weinberg equilibrium, the equation _______________ can be used to calculate genotype frequencies.

Answer 2

p^2 + 2pq + q^2 = 1

Question 3

T or F: the highest expected frequency of the heterozygous genotype would be when p = q = 0.5, 2pq = 0.5.

Answer 3

True

Question 4

T or F: two generations of random mating in a mixed population produces Hardy-Weinberg equilibrium frequencies for genotypes

Answer 4

False, only one generation

Question 5

The six assumptions of HWE are….

Answer 5

(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

Question 6

The four predictions of HWE are….

Answer 6

(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

Question 7

When there are three alleles and you are calculating expected genotype frequencies, __________ = 1 and ________________________ = 1

Answer 7

(p + q + r)^2 = 1
p^2 + q^2 + r^2 + 2pq +2pr + 2qr = 1 - [6 possible genotypes]

Question 8

What are the two methods for determining autosomal allele frequencies from genotype frequencies in diploids?

Answer 8

(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

Question 9

There are three major sources of genetic variability and two population-environment interactions that contribute to evolution

Answer 9

Mutation, Mode of Reproduction, Gene Flow + Natural Selection, Genetic Drift

Question 10

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.

Answer 10

True

Question 11

In a model of natural selection favoring the heterozygous genotype, pE = _________ & qE = ________, where t = _______ & s = _______.

Answer 11

pE = t / ( s + t )
qE = s / ( s + t)
t = 1 - w (q^2)
s = 1 - w (p^2)

Question 12

Mutation is…

Answer 12

the ultimate source of all new genetic variation in populations

Question 13

Forward mutation rate VS Reverse mutation rate

Answer 13

the rate of creating new alleles, the rate of mutation to original allele

Question 14

Gene Flow can…. (4 things)

Answer 14

(1) introduce new alleles
(2) increase frequency of existing alleles
(3) remove/reduce existing alleles
(4) create admixed population

Question 15

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.

Answer 15

the Island Model

Question 16

Genetic Drift refers to

Answer 16

chance fluctuations of allele frequencies due to “sampling bias”

Question 17

Genetic drift occurs in all populations but is especially prominent in _____ populations

Answer 17

small

Question 18

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.

Answer 18

True

Question 19

Inbreeding results in an increase of _________ genotypes.

Answer 19

homozygous

Question 20

T or F: inbreeding changes allele frequencies while also systematically redistributing the alleles into genotypes that increase homozygosity, while reducing heterozygosity

Answer 20

False, the second portion is true though.

Question 21

Inbreeding Depression

Answer 21

the reduction in fitness of inbred organisms, often due to reduced genetic heterozygosity.

Question 22

Biological Species Concept (BSC)

Answer 22

the most widely used definition of a species - a group of organisms capable of interbreeding with each other but isolated from other species

Question 23

4 Things wrong with BSC

Answer 23

(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)

Question 24

Allopatric Speciation

Answer 24

populations diverge due to physical barrier, causing new species to develop in separate geographic locations

Question 25

Sympatric Speciation

Answer 25

populations share a territory but are isolated by genetic, behavioral, seasonal, or ecosystem-based mechanisms that prevent gene flow

Question 26

Hybrid Speciation

Answer 26

formation of a new species due to hybridization between existing species

Question 27

List the Mechanisms of Reproductive Isolation

Big Gay Guys Hate My Teeth

Answer 27

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

Question 28

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.

Answer 28

True