Chapter 26

Front 1

Natural Selection

Back 1

increase the freq of certain alleles (i.e. the ones that contribute to reproductive success in a particular environment)

Front 2

Genetic Drift

Back 2

causes allele frequencies to change randomly

may cause alleles that decrease fitness to increase in fitness

Front 3

Gene flow

Back 3

when individuals leave one population, join another, and breed.

Movement of alleles between populations.

-it equalizes allele frequencies between the source population and the recipient population

-Random with respect to fitness

Front 4

Mutation

Back 4

modifies allele frequencies by continually introducing new alleles

-increases genetic diversity in population (ultimate source)

Front 5

Hardy-Weinberg

Back 5

Important null hypothesis that can show that no other evolutionary processes are taking place (mating was random with respect to the gene)

Key: is a theoretical approach – this almost never happens!

Front 6

State the two equations for the Hardy-Weinberg Principle

Back 6

Allele freq: p+q=1

Genotype freq: p^2+2pq+q^2=1

Front 7

What five assumptions must be met for the Hardy-Weinberg Principle?

Back 7

1) Random mating - picking gamete from gene pool at random
2) No natural selection - all parental generations survived and contributed an equal number of gametes
3) No genetic drift - alleles picked in their exact frequencies
4) No gene flow - no new alleles added or lost
5) No mutation - didn't consider other new alleles being added to gene pool

Front 8

Gene pool

Back 8

single group of alleles from gametes in each generation

Front 9

Inbreeding

Back 9

-mating between relatives

Two points

1) increase in homozygosity, decreases heterozygosity
2) doesn't cause evolution because allele freq do not change in population as a whole

Front 10

How can inbreeding speed up the rate of evolutionary change?

Back 10

it gets rid of recessive deleterious alleles(alleles that lower fitness) from a population.

Front 11

Inbreeding Depression

Back 11

the decline in average fitness that takes place when homozygosity increases and heterozygosity decreases in a population

Front 12

Heterozygote advantage

Back 12

Heterozygous individuals have higher fitness than homozygous individuals do.

Example: Sickle cell trait

in people with sickle cell trait, the red blood cells are resistant to malaria infection. That means people with the trait are protected from the disease, and have an advantage over people without sickle cell trait.

Front 13

Sexual selection

Back 13

courtship success

Sexual selection can take the form of:

Intersexual selection---- or mate choice

Intrasexual selection---- where individuals compete for mates

mechanism of evolutionary change

Front 14

Genetic variation

Back 14

the number and relative frequencies of alleles that are present in a particular population, decreases genetic drift

Front 15

Directional selection

Back 15

avors one extreme phenotype, causing average phenotype in pop to change in one direction, genetic variation is reduced

Front 16

Stabilizing selection

Back 16

favors phenotypes near the middle of the range of phenotypic variation, maintaining average phenotype, genetic variation is reduced

Front 17

Disruptive selection

Back 17

favors extreme phenotypes at both ends of range of phenotypic variation, genetic variation increases

Front 18

Balancing selection

Back 18

no single phenotype is favored in all populations of a species at all times, genetic variation is maintained

Front 19

Purifying selection

Back 19

when the disadvantageous alleles decline in frequency

a part of directional selection

Front 20

Intersexual selection

Back 20

one mate choosing to mate with another mate of different genders

Front 21

Intrasexual selection

Back 21

mates of the same gender fighting over the opposite gender

Front 22

Fundamental asymmetry of sex

Back 22

females invest much more in their offspring than males

Front 23

Sexual dimorphism

Back 23

refers to traits that differ between male and female

Front 24

Genetic drift

Back 24

change in allele frequencies in a population due to chance

-more impactful on small populations

Front 25

Gene flow

Back 25

The movement and exchange of genes or alleles from one population of species to another

Gene flow homogenizes (makes similar) populations

Front 26

Sampling error

Back 26

The deviation of a result in a scientific experiment from the true result. As a rule of thumb, larger scale experiments have a lower sampling error (all things being equal bar the differentiating factor of the experiment). A larger scale represents a more apparent trend when the data has been collected to back a hypothesis or prove it wrong.

Front 27

Genetic markers

Back 27

specific alleles that cause a distinctive phenotype

Front 28

Founder event

Back 28

occurs when a group starts a new population in a new area

in small groups, allele frequencies probably differ from the source population

Front 29

Founder effects

Back 29

change in allele frequencies with the creation of a population that follows a founder event.

-equalizes frequencies between source and recipient populations

Front 30

Population Bottleneck

Back 30

A sudden decrease in population size

Caused by?

-disease outbreaks or natural catastrophes

lead to genetic bottlenecks

Front 31

genetic bottlenecks

Back 31

a sudden reduction in the number of alleles in a population.

Drift occurs during genetic bottlenecks and causes a change in allele frequencies

Front 32

Deleterious alleles

Back 32

alleles that lower fitness

Front 33

genetic isolation

Back 33

is population of organisms that has little genetic mixing with other organisms within the same species. This may result in speciation, but this is not necessarily the case.

Front 34

What is the difference between genetic drift and gene flow?

Back 34

Genetic drift - causes allele frequencies to change randomly, not selection of fitness

Gene flow - occurs when individuals leave one population, join another, and breed

Front 35

Does nonrandom mating change both genotype frequency and allele frequency?

Back 35

it only changes genotype frequency

Front 36

What are the three key points for genetic drift? Where does genetic drift impact the most?

Back 36

1) it is random with respect to fitness
2) most pronounced in small populations
3) lead to random loss or fixation of alleles

most pronounced in small populations and has a big impact

Front 37

What are two examples of genetic drift?

Back 37

1) founder effect = immigrants establish new population

2) genetic bottleneck = high mortality strikes at random

Front 38

What would happen to evolution if there was no mutation?

Back 38

Evolution would eventually stop because there would be no variation for selection and drift to act on.

Front 39

How did diversity come to be?

Back 39

mutation, natural selection

(change in allele frequencies)

Front 40

What should happen.. if no evolution?

Back 40

allele frequency would stay the same

Front 41

If genetic drift decreases, what happens to genetic variation within the population and between the population?

Back 41

genetic drift decreases genetic variation within population and increase genetic differences between populations

Front 42

Movement of alleles between populations tends to reduce their what?

Back 42

genetic differences
(variation within population increases)

Front 43

Explain why genetic drift leases to a random loss or fixation of alleles

Back 43

when allele frequencies fluctuate randomly up and down, sooner or later the frequency of an allele will hit 0.

that allele is lost from the population, and the other allele is fixed

Front 44

Explain why genetic drift is particularly important as an evolutionary force in small populations.

Back 44

in small populations, sampling error is large. The accidental death of a few individuals would have a large impact on allele frequencies

Front 45

Why does natural selection violate the Hardy-Weinberg principle?

Back 45

the hardy-weinberg principle predicts that allele frequencies will stay the same over time. natural selection favors some allele over others causing the frequency of those alleles to increase