Chapter 21

Question 1

Evolutionary impact of natural selection is only apparent in how ____________ changes

Answer 1

Populations

Question 2

Microevolution

Answer 2

A change in allele frequencies in a population over generations

Question 3

3 mechanisms for causing allele frequency change

Answer 3

1. Natural selection
2. Genetic Drift
3. Gene flow

Question 4

Genetic variation at the whole gene level can be quantified as what?

Answer 4

As the average percentage of loci that are heterozygous

Question 5

Neutral variation

Answer 5

Differences in DNA sequences that do not confer a selective advantage or disadvantage

Ex: which thumb is on top when you hold hands

Question 6

What mechanisms cause shuffling of alleles and deals them at random

Answer 6

Crossing over, independent assortment, and fertilization

Question 7

Population

Answer 7

A group of individuals of the same species that live in the same area and interbreed producing fertile offspring

Question 8

Gene pool

Answer 8

Consists of all copies of every type of allele at every locus in all members of the population

-if all only one allele exists in a population then it is said to be fixed in the gene pool.

Question 9

Allele and gene frequencies change over time of one of 5 of the following are no met….

Answer 9

1. No mutations
2. Random mating (leads to interbreeding= less gene mixing)
3. No natural selection
4. Extremely large pop size
5. No gene flow (no immigration or emigration)

Question 10

Adaptive evolution

Answer 10

Consistently favouring some alleles over others. A process in which traits that enhance survival or reproduction increase in frequency over time.

Question 11

Genetic drift

Answer 11

A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects are most noticeable in small populations

Question 12

Founder effect

Answer 12

When a few individuals become isolated from the larger population and form smaller groups whose gene pools differ from the source population

Question 13

Bottleneck effect

Answer 13

Population size has been reduced and by chance, certain alleles may be over represented among survivors

Question 14

Gene flow

Answer 14

The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes (migration)

Question 15

Relative fitness

Answer 15

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

Question 16

Directional selection

Answer 16

Occurs when conditions favour one extreme of a phenotypic range, thereby shifting a pop. frequency for the phenotypic character in one direction.

Ex: all Moses are now white coated

Question 17

Disruptive selection

Answer 17

Selection leads to the extreme but not to intermediates

Ex: all mice are light or dark coloured

Question 18

Stabilizing selection

Answer 18

Selection leads to favour intermediates and away from extremes

Ex: All mice are brown

Question 19

Balancing selection

Answer 19

Natural selection that maintains two or more phenotypic frequencies in a pop.

Question 20

Heterozygote advantage

Answer 20

Greater reproductive success of heterozygous individuals compared to homozygous. (Preserves variation in a gene pool)

Ex: sickle cell disease (in heterozygous state you are mostly normal but mosquitoes do not like you)

Question 21

Frequency-dependent selection

Answer 21

The fitness of a phenotype depends on how common it is in the population

When one does better when Other doesn’t in a population of a species with 2 variants

Ex: right and left mouthed fish

Question 22

Sexual selection

Sexual dimorphism

Answer 22

Individuals with certain inheritance traits are more likely to obtain mates

A difference in secondary sexual characteristics between males and females of the same species. (Peacocks)

Question 23

Intrasexual selection

Answer 23

Selection within the same sex

Ex: males compete with each other for females (stronger males reproduce more)

Question 24

Somatic and Germ line

Answer 24

Non reproductive cells

Reproductive cells

Question 25

Hardy- Weinberg equation

Answer 25

To test whether a population is evolving

P2+2Pq+q2=1

Question 26

Allelic frequency

Answer 26

of individuals of a particular type out of the total number of alleles of that gene

Question 27

Genotypic frequency

Answer 27

of individuals of a particular genotype out of the total # of individuals in the population

Question 28

If the allelic frequency of a population does not change from one generation to the next than the population is at _______ and therefore ______

Answer 28

Hardy-Weinberg equilibrium

Not evolving

Question 29

Effects of gene drift

Answer 29

• significant in small populations
• cause allelic frequencies to change at random
• lead to loss of genetic variation within a pop
• cause harmful alleles to become fixed

Question 30

Intersexual selection

Answer 30

“Mate choice” often females choose the males

Question 31

Evolutionary compromise example

Answer 31

Mating call of frog attracts a mate but also predators