Lecture 6 & 7 Evolution II

Question 1

what is microevolution?

Answer 1

change in allele frequencies in populations over generations

Question 2

what is a gene/genetic locus?

Answer 2

the combination of two alleles (in diploid individuals)

Question 3

what is a population?

Answer 3

a group of organisms that interbreed (share a gene pool) and produce fertile offspring

Question 4

what is a gene pool?

Answer 4

all the alleles for all loci in a population

Question 5

what are the three factors that can change allele frequency?

Answer 5

1. natural selection
2. genetic drift
3. gene flow

Question 6

which factor is the only one that can cause adaptive evolution?

Answer 6

natural selection

Question 7

what is a phenotype?

Answer 7

a product of inherited genotype and environmental factors

Question 8

what are discrete characters?

Answer 8

• typically a single locus with alternative alleles

Question 9

what are quantitative characters?

Answer 9

characters which vary along a continuum within a population

Question 10

what is geographic variation?

Answer 10

differences between gene pools of separate populations

Question 11

what is a cline?

Answer 11

a graded change in a trait along a geographical axis - displays geographic variation

Question 12

what are sources of genetic variation?

Answer 12

• mutations

- gene duplication (ex: sexual reproduction shuffling new genes)

Question 13

what are mutations?

Answer 13

changes in an individual’s nucleotide sequence

• can be caused by damage in DNA replication or structural damage to DNA
• only mutations in cells that produce games can be passed to offspring
• random

Question 14

what are macromutations?

Answer 14

• very large mutations

Question 15

what is more important for sexually reproducing organisms: mutations or shuffling?

Answer 15

• shuffling/recombination

Question 16

what are the three types of natural selection?

Answer 16

• directional
• disruptive
• stabilizing

Question 17

what is directional selection?

Answer 17

• extreme is favoured, variance remains the same

Question 18

what is disruptive selevtion

Answer 18

• favours individuals in both extremes of phenotypic range
• results in POLYMORPHISM
• maintains variation

Question 19

what is stabilizing selection?

Answer 19

• favours intermediate/common variants
• selects against extreme phenotypes
• mean stays the same
• variance decreases
• little or no evolutionary change

Question 20

what is polymorphism?

Answer 20

• 2 or more divergent phenotypes

- result of disruptive selection

Question 21

what is genetic drift?

Answer 21

• changes in allele frequency due to chance
• significant in small pop’ns
• lead to a loss of genetic variation w/in populations
• can cause harmful alleles to become fixed
• bottleneck and founder effect

Question 22

how do allele frequencies drift?

Answer 22

from one generation to the next

Question 23

what size of populations does genetic drift affect the most?

Answer 23

small populations

Question 24

what is the bottleneck effect?

Answer 24

• sudden reduction to pop’n size because of environmental change
• allele frequency in next gen is different than previous
• rare alleles more likely to be lost because of drift

Question 25

what is the founder effect?

Answer 25

- new population is established by a few colonizers isolated from the larger population - small fraction of total genetic variation compared to the ancestral population -- change in allele frequency

Question 26

what is gene flow?

Answer 26

the transfer of alleles between populations - can introduce new variation - tends to slow local adaptation and reduce variation among populations over time

Question 27

what does gene flow do to fitness?

Answer 27

- both increases and decreases fitness

Question 28

what is sexual dimorphism?

Answer 28

- marked differences between the sexes in secondary sexual characteristics

Question 29

what is sexual selection?

Answer 29

- selection for the acquisition of more or better mates - category within natural selection - NS for mating success

Question 30

what are the two types of sexual selection?

Answer 30

- intrasexual | - intersexual

Question 31

what is intrasexual selection?

Answer 31

- competition among individuals of one sex for mates of the opposite sex - ex: large antlers in male deer for fighting - result of physical competition for access to mates

Question 32

what is intersexual selection?

Answer 32

- mate choice - when individuals of one sex choose in mate selection - flashy plumage or dances - usually females choose males and males are flashy

Question 33

what did Darwin think about sexual selection?

Answer 33

- separated SS and NS because it seemed like some sexually selected traits act against naturally selected ones - flashy plumage -- predators - but the same is said for many traits - long life against faster growth

Question 34

what is another factor that brings about evolutionary change?

Answer 34

extinction

Question 35

what is neutral variation?

Answer 35

- genetic variation that doesn't confer a selective advantage or disadvantage

Question 36

what are seven mechanisms that maintain genetic variation in populations?

Answer 36

``` mutation recombination independent assortment of alleles fertilization disruptive selection gene flow balancing selection ```

Question 37

what is balancing selection? | what does it include? (2)

Answer 37

occurs when NS maintains stable frequencies of two or more phenotypic forms in a population - includes heterozygote advantages - frequency dependent selection

Question 38

what is heterozygote advantage?

Answer 38

balancing selection occurs when heterozygotes have a higher fitness than do both homozygotes - NS maintains 2 or more alleles at that locus - ex: sickle cell and malaria

Question 39

what is frequency - dependent selection?

Answer 39

balancing selection - fitness of phenotype declines if it becomes too common in a population - rare genotype has a selection advantage

Question 40

why can't NS fashion perfect organisms?

Answer 40

1. NS can act ONLY on existing variations 2. evolution is limited by historical constraints 3. adaptations are often compromises 4. chance, NS, and the environment interact

Question 41

what are the two modes of evolution? | what is in between?

Answer 41

- microevolution - macroevolution - in between is speciation

Question 42

what is microevolution?

Answer 42

- evolution at the population level - changes allele frequency in a population over time - occurs mainly through selection - results in adaptation - or drift

Question 43

what is macroevolution?

Answer 43

- evolutionary changes ABOVE species level - origin of complex novel characters - appearance of higer taxa - mass extinctions