8/23 microevolution

Question 1

Causes of microevolution
(changes in allele frequencies)
1) Genetic Mutations
_____________________ in the gene
Mutation rates are low
Mutations can be lethal, neutral or beneficial
Cause change in frequencies (creation of a new allele)
Only “________” source of genetic variation

Answer 1

1. Change (error)
2. new

Question 2

Causes of microevolution
(changes in allele frequencies):
2) Gene Flow
Organisms or their gametes (ex. pollen) may move from _________________________________
If immigrants reproduce, may introduce __________________, changing allele and gene frequency of the population
Importance of gene flow depends on degree of genetic differentiation between populations and rate of gene flow

Answer 2

1.one population to another
2.novel alleles

Question 3

2) Gene Flow
Movement of alleles among populations
Alleles can be transferred through the movement of fertile ________________ or _______________
Gene flow tends to reduce differences between populations over time
Gene flow is more likely than _______________ to alter allele frequencies directly

Answer 3

1.individuals
2.gametes
3.mutation

Question 4

Causes of microevolution:
3) Nonrandom Mating
Individuals do not choose _________________________
-Assortative mating - Individuals tend to mate with those with __________ phenotypes
-Sexual selection - Males compete for the right to reproduce. Females ___________ to mate with males possessing a particular phenotype

Answer 4

1.who to mate with
2.similar
3. select

Question 5

Causes of microevolution:
4) Genetic Drift

-Changes in allele frequencies of a gene pool due to chance (________________)
-Generally leads to ___________ genetic variability due to loss of __________ alleles

-Large populations ►►► ____________ impact

-Smaller populations ►►► ___________ impact

Answer 5

1.Random
2.reduced
3.rare
4.little
5.large

Question 6

Special Cases of Genetic Drift:
A) Bottleneck Effect
An event ____________________ a majority of genotypes from entering the next generation (ex. disease, starvation, drought, etc.)

Answer 6

1. that prevents

Question 7

Special Cases of Genetic Drift:
B) Founder Effect
-___________________________
-Only carry a ____________________ of the alleles
Change in allele frequencies when a new population arises from only a few individuals

Answer 7

1.Few individuals establish a new population
2.small amount

Question 8

Founder Effect example:
-All individuals exhibiting syndrome are _________________ ___________ who helped found the community in the 1700s

Answer 8

1.descended from a couple

Question 9

Conservation Implications of Genetic Drift:
-Endangered species experience population _______________, which leads to decreased genetic diversity
-Small number of individuals used for captive breeding programs may not represent species ___________________________
-With low genetic diversity, recovered populations may still be _________resistant or less able to cope with environmental changes

Answer 9

1.bottlenecks
2.genetic diversity
3.less

Question 10

Conservation Implications of Genetic Drift:
Example:
-Populations are susceptible to ____________, males have high proportions of abnormal _________, reduced reproductive capacity
-Limited _____________ variability and small numbers threaten endangered populations

Answer 10

1.disease
2.sperm
3.genetic

Question 11

Causes of microevolution :
5) Natural Selection
Although selection changes the frequency of alleles in a population, it is the phenotype of an individual, rather than a particular allele, that is successful or not
Requirements:
-__________________________(variation among population members and differences are heritable)
-_________________________(some survive better than others)
-____________________________(some reproduce more than others)

Answer 11

1.Heritable variation
2.Differential Survival
3.Differential Reproduction

Question 12

Types of Selection:
3 modes of natural selection
1._______________
2._______________
3._______________

Answer 12

1.Directional
2.Stabilizing
3.Disruptive

Question 13

1. Directional Selection
   -_____________ phenotypes is the most fit (favored)
   -Distribution curve shifts in that direction
   Can occur when a population is adapting to a changing environment

Answer 13

1.Extreme

Question 14

2. Stabilizing (Balancing) Selection:
   An _____________ phenotype is favored

Example: Clutch sizes in birds
Intermediate # of eggs (High survivability)
Too many eggs (Low survivability many starve)

Example: ______________ in humans

Answer 14

1.intermediate
2.birth weights

Question 15

3. Disruptive Selection:
   -Two or more extreme phenotypes are favored over any intermediate phenotype
   -Intermediate phenotypes have ______________________
   Two distinctly different phenotypes are found in the population
   -__________ common in nature compared to directional or stabilizing selection

Answer 15

1.lower fitness
2.the least

Question 16

Hardy-Weinberg Equilibrium:
-When a population achieves genetic equilibrium (point when neither gene or allele frequencies change in succeeding generations)
-Used to test whether a population is evolving
Gene pool of an idealized, non evolving *population that remains __________________over generations
*Describes how genotype frequencies in a population relate to allele frequencies in the ______________of evolution

Answer 16

1.constant
2.absence

Question 17

Hardy-Weinberg Equilibrium:
According to this model, genetic equilibrium is possible only if all of the following are met:
1.NO ______________________
2.NO _____________________(no immigrants or emigrants)

Answer 17

1.mutations
2.gene flow

Question 18

According to this model, genetic equilibrium is possible only if all of the following are met:
3.Population is infinitely _____________________
4.NO ____________________________ (all genotypes in population survive and reproduce equally as well)
5.______________ mating

Answer 18

3.large
4.natural selection
5.random

Question 19

Hardy-Weinberg Equilibrium
Calculate genotype frequencies with a binomial expansion
(p+q)2 = p2 + 2pq + q2

______ = individuals homozygous for first allele
______ = individuals heterozygous for alleles
______ = individuals homozygous for second allele

p2 + 2pq + q2

and
p+q = 1
(always two alleles)

Answer 19

1.p^2
2.2pq
3.q^2

Question 20

Hardy-Weinberg
Allele frequencies remain constant……

If there are……
1) No ________________________
2) No ___________________
3) Population is infinitely large
4) No natural selection
5) Random ______________

Answer 20

1. mutations
2. gene flow
3. population is infinitely large
4. No natural selection
5. mating