Chapter 19

Question 1

What is a population?

Answer 1

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

Question 2

In herds, is interbreeding with other herds common?

Answer 2

No, there is a better chance for two populations to interbreed than two different herds

Question 3

What is the smallest unit of evolution?

Answer 3

populations

Question 4

True or False: Natural selection acts on individuals, but only populations evolve.

Answer 4

true

Question 5

What is a “prerequisite” for evolution?

Answer 5

Variation in hertiable traits

Question 6

What are differnces among individuals in the composition of their genes called?

Answer 6

Genetic Variations

Question 7

What is a genotype?

Answer 7

the genetic constitution of an organism

Question 8

What is a phenotype?

Answer 8

the product of an inherited genotype and many environmental influences

Question 9

Are mutation rates slow or fast in eukaryotes?

Answer 9

They are slow in plants and animals

Question 10

Are mutation rates slow or fast in prokaryotes?

Answer 10

Mutations accumulate quickly in bacteria and viruses’ because they have short generation times (doubles really fast)

Question 11

Can all mutations be heritable?

Answer 11

No, only mutations in cells that produce gametes (sperm & egg (germ-line cells)) can be passed to offspring

Question 12

Processes in which sexual reproduction can result in genetic variation by recombing existing alleles:

Answer 12

• Crossovers (exchange of alleles)
• Independent assortment
• Random fertilization (64 trillion possible combinations of genes)

Question 13

What is are “fixed” alleles?

Answer 13

it means the alleles are homozygous in all individuals
Basically, an allele that is the only variant that exists for a gene in a population

Question 14

What is genotypic frequency?

Answer 14

% The proportion of each genotype in the population

Question 15

What is allele frequency?

Answer 15

% The proportion of each allele in the population

Question 16

What is an allele?

Answer 16

2 or more alternative forms of a gene that arise by mutation

Question 17

What is microevolution?

Answer 17

It is the change of allele frequencies in a population over generations; an evolving population that is showing genetic change over generations

Question 18

What is population genetics?

Answer 18

It is the study of what changes the allele frequencies in populations

Question 19

What are the three mechanisms of microevolution and cause allele frequency?

Answer 19

• Natural selection
• genetic drift
• gene flow

Question 20

What is genetic drift?

Answer 20

The change in genetic frequencies due to random events; often occurs in small populations

founder effect and bottleneck effect

Question 21

outcomes of genetic drift?

Answer 21

• random changes in allele frequency in either direction
• often reduces genetic diversity
• one allele may become fixed

Question 22

What is gene flow?

Answer 22

When alleles move in or out of a population

Question 23

What is adaptive evolution?

Answer 23

It is when natural selection only acts on the population’s heritable traits- selects for beneficial alleles, and thus, increases thier frequency in the population, while it selects against deleterious alleles and thus decreases their frequency.

Always leads to the adaption of a population to the current environment

Question 24

The Hardy-Weinburg Equilibrium

Answer 24

If a large population reporduces sexually at random, then the genetic frequencies should not chnage in the next generation (remains in equilibrium

Question 25

The Hardy-Weinberg conditions

Answer 25

- No mutations - Mating is random - No selection (equal survival) - Very large population size - No gene flow in or out

Question 26

What is a Punnet Square?

Answer 26

A square diagram that is used to predict the genotypes of a particular cross

Question 27

frequency dominant allele

Answer 27

=p

Question 28

frequent recessive allele

Answer 28

=q

Question 29

frequency of dominant homozygous genotype

Answer 29

=p^2

Question 30

frequency of heterozygous genotype

Answer 30

= 2pq

Question 31

Frequency of recessive homozygous genotype

Answer 31

= q^2

Question 32

Results of natural selection:

Answer 32

- acts non-randomly on phenotypes of individuals; favorable allele - changes in allelic and genotypic frequencies of populations non-randomly - Always leads to the adaption of the population to the current environment

Question 33

The founder's effect & genetic drift

Answer 33

When a few founders start a new isolated population because of genetic dirft it causes the later generations to be random, less diverse founder population, more genetic drift, some adaptive alleles are lost ## Footnote Example: high rate of inherited blindness on Tristan da Cuhna - Maldaptive allele frequency increases - 250 descendants from 15 settlers

Question 34

The bottleneck effect & genetic drift

Answer 34

An event that drastically cuts the population size such as a flood or any type of natural disaster

Question 35

Gene flow includes:

Answer 35

- Migration of adults - dispersal of gametes - allele difference is low because of gene flow

Question 36

outcomes of natural selection on a population depend on:

Answer 36

- relative fitness - forms of natural selection - sexual selection - limitations of natural selection

Question 37

What is relative fitness?

Answer 37

The contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals - Fitness is relative to other individuals in the population ## Footnote "fittest"- means best reproductive success

Question 38

# forms of natural selection What is directional selection?

Answer 38

- selects for the phenotypes at one end of the spectrum of the existing variation - shifts the population's genetic variance toward the new, fit phenotype

Question 39

# forms of natural selection What is diversifying selection?

Answer 39

- Intermediates are less fit than extremes - maintains diversity - increases genetic variance ## Footnote aka disruptive selection

Question 40

# forms of natural selection What is stabilizing selection?

Answer 40

- intermediates types more fit than extremes - decreases genetic variance | favors average phenotypes

Question 41

# forms of natural selection What is frequency-dependent selection?

Answer 41

- the fitness of a phenotype depends on how common it is in the population ## Footnote the scale-eating fish, that was pointed left wards or towards the right

Question 42

What is sexual selection?

Answer 42

A process in which indivduals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates ## Footnote example: size, color, ornamentation, behavior

Question 43

What is sexual dismorphism?

Answer 43

Phenotypic difference between a population's males and females

Question 44

What is intrasexual selection?

Answer 44

Individuals of one sex compete directly for mates of the opposite sex

Question 45

What is Intersexual Selection

Answer 45

individuals of one sex (usually the females) are choosy in selecting their mates from the other sex ## Footnote also called mate choice

Question 46

What is macroevolution?

Answer 46

broader scale evolutionary changes that scientists see over paleontological time

Question 47

Does natural selection make perfect organisms?

Answer 47

no