Ch21 : microevolution: genetic change within populations

Question 1

microevolution

Answer 1

small-scale genetic changes within populations, often in response to shifting environmental circumstances or chance events

Question 2

population

Answer 2

a group of organisms of the same kind that live together in the same place

Question 3

phenotypic variation

Answer 3

differences in appearance/ function between individual organisms

Question 4

quantitative variation

Answer 4

variation that is measure on a continuum rather than categories . Data vary continuously over an range of measurements. Data exists in discrete(5) or continuous form (0.5)

Question 5

qualitative variation

Answer 5

variation that exists in 2 or more discrete states, with intermediate forms often being absent. Data varies discontinuously

Question 6

polymorphism

Answer 6

the existence of discrete variants of a character among individuals in a population

Question 7

gene pool

Answer 7

the sum of all alleles at all gene loci in all individuals in a population

Question 8

genotype frequency

Answer 8

the percentage of individuals in a population possessing a particular genotype

Question 9

allele frequency

Answer 9

the abundance of one allele relative to others at the same gene locus in individuals of a population

Question 10

null model

Answer 10

a conceptual model that predicts what one would see if a particular factor had no effect

Question 11

Hardy weinberg principle

Answer 11

an evolutionary rule of thumb that specifies the conditions under which a population of diploid organisms achieves genetic equilibrium

Question 12

genetic equilibrium

Answer 12

the point at which neither the allele frequencies not the genotype frequencies in a population change in succeeding generations

Question 13

mutation

Answer 13

a spontaneous and heritable change in DNA

Question 14

gene flow

Answer 14

the transfer of genes from one population to another through the movement of individuals or their gametes

Question 15

genetic drift

Answer 15

random fluctuations in allele frequencies as a result of chance events; usually reducing genetic variation in a population

Question 16

founder effect

Answer 16

an evolutionary phenomenon in which a population that was established by just a few colonizing individuals has only a fraction of genetic diversity seen in the population from which it is derived

Question 17

natural selection

Answer 17

the evolutionary process by which alleles that increase the likelihood of survival and the reproductive output of the individuals that carry them become more common in subsequent generations

Question 18

relative fitness

Answer 18

the number of surviving offspring that an individual produces compared with the number left by others in the population

Question 19

directional selection

Answer 19

a type of natural selection in which individuals near one end of the phenotypic spectrum have the highest relative fitness

Question 20

stabilizing selection

Answer 20

a type of natural selection in which individuals expressing intermediate phenotypes have the highest relative fitness

Question 21

disruptive selection

Answer 21

a type of natural selection which extreme phenotypes have higher relative fitness than intermediate phenotypes

Question 22

sexual selection

Answer 22

a form of natural selection established by male competition for access to females and by females’ choice of mates

Question 23

sexual dimorphism

Answer 23

differences in the size or appearance of males and females

Question 24

inbreeding

Answer 24

a special (haha) form of non random mating in which genetically related individuals mate with each other

Question 25

balanced polymorphism

Answer 25

the maintenance of 2 or more phenotypes in fairly stable proportions over many generations

Question 26

heterozygote advantage

Answer 26

an evolutionary circumstance in which individuals that are heterozygous at a particular locus have higher relative fitness than either homozygote

Question 27

frequency dependent selection

Answer 27

a form of natural selection in which rare phenotypes have a selective advantage simply because they are rare

Question 28

neutral variation hypothesis

Answer 28

an evolutionary hypothesis that some variations at gene loci coding for enzymes and other soluble proteins is neither favored nor eliminated by natural selection

Question 29

adaptive trait

Answer 29

a genetically based characteristic, preserved by natural selection, that increases an organism's likelihood of survival or its reproductive output

Question 30

adaptation

Answer 30

characteristic that helps an organism survive longer or reproduce more under a particular set of environmental conditions

Question 31

within a given population there is phenotypic variation. what is the shape if you had to quantify it (number of individuals on the y axis and the measurement of the trait on the x)? what does a broad , low curve entail? what does a high, narrow curve entail?

Answer 31

- bell shaped curve - broad, low curve= lots of variation among individuals - narrow, high curve= little variation

Question 32

example of polymorphism

Answer 32

peppered moth

Question 33

phenotypic variation within a population is caused by 3 things and ex

Answer 33

1. genetic differences between individuals (differences in parts of genotype) 2. differences in environmental factors that individuals experience e.g acidity in soil influences flower colour in some plants 3. interactions between genetics and the environment

Question 34

2 main processes that generate genetic variation

Answer 34

1. production of new alleles - arise from small scale mutations 2. rearrangement of existing alleles into new combinations can result from : - crossing over between homologous pairs during meiosis - independent assortment of non-homologous chromosomes during meiosis - random fertilization between genetically different sperm and eggs

Question 35

2 of Hardy- Weinberg's formula

Answer 35

p+q=1 | p^2 +2pq +q^2 = 1

Question 36

genetic equilibrium is possible if and only if all 4 of these conditions are met

Answer 36

1. no mutations are occurring 2. the population is closed to migration from other populations 3. the population is infinitely large 4. all genotypes in the population survive and reproduce equally well

Question 37

what are the 5 agents of microevolution

Answer 37

1. mutation 2. gene flow 3. genetic drift 4. natural selection 5. non-random mating

Question 38

4 types of mutation

Answer 38

1. deleterious 2. lethal 3. neutral 4. advantage

Question 39

how does gene flow take place in plants since they are stationary + 2 ex

Answer 39

through dispersal agents e.g the wind , seed-carrying animals. ex: birds carry acorns from one oak population to another

Question 40

genetic drift reduces variability within populations. Does it have a greater effect on large/ small populations and why?

Answer 40

small populations because only a few individuals contribute to the gene pool and because any given allel may be present in very few individuals

Question 41

what are 2 circumstances that foster genetic drift

Answer 41

1. population bottle necks | 2. founder effect

Question 42

what is a population bottleneck

Answer 42

a drastic reduction in population size due to a stressful factor e.g. disease or a drought. This cause of genetic drift reduces variation and rare genes are inevitably lost

Question 43

what form of genetic drift do endangered species experience +ex

Answer 43

severe population bottlenecks, which result in loss of genetic variability e.g cheetahs today are pretty uniform in their genetic make up making them highly susceptible to disease , etc

Question 44

3 modes of natural selection

Answer 44

1. directional 2, stabilizing 3. disruptive

Question 45

what is the shape of a disruptive mode of natural selection

Answer 45

bimodal

Question 46

sexual selection often exaggerates showy features in males examples

Answer 46

brightly coloured feathers, tails, as well as courtship behaviour (behaviour designed to attract females)

Question 47

sexual selection encompasses 2 related processes

Answer 47

1. intersexual selection : selection based on the interations between males and females, e.g. showy structures 2. intrasexual selection: based on interactions between members of the same sex, males use for example their large size to intimidate or injure competing males

Question 48

how can much variation persist under the action of stabilizing selection and genetic drift 3 ways

Answer 48

1. diploidy can mask recessive traits from the action of natural selection 2. natural selection can maintain balanced polymorphisms 3. some genetic variations may be selectively neutral

Question 49

what is the most probable cause of sexual polymorphism and an ex

Answer 49

cause= sexual selection | e.x. female peacocks have short, dull, brown tails while males have long colourful tails

Question 50

natural selction can maintain balance polymorphisms through 3 things

Answer 50

1. heterozygote advantage 2. different alleles are favored in different environments 3. frequency dependent selection

Question 51

example of heterozygote advantage

Answer 51

Hbs (sickle) allele that codes for a defective form of haemoglobin. Homozygous Hbs-Hbs individuals often die of sickle cell anemia before reproducing, Heterozygous individuals often survive malaria because the shape of the blood cells offers difficulties for the protist. heterozygous Hbs-HbA(normal) have higher relative fitness in malaria prone areas than homozygous HbA-HbA. And so the allele is preserved.

Question 52

example of how different alleles are favored in different environments

Answer 52

European garden snails exist in a range of colours. This polymorphism is conserved by the selection for camouflage in different habitats. Thrushes are visual predators,well camouflaged snails survive. Success varies with habitat e.g. the brown unstripped predominate in woods covered with leaves

Question 53

an example of frequency dependent selection

Answer 53

the Elderflower orchid exists as yellow and purple flowers. Bumble bees prefer the more rare flowers to pollinate. Therefore the reproductive success of the plant is higher when its colour is rare. When the yellow =rare they get pollinated more and are no longer rare and so then the bumble bees prefer the purple. its continuously shifting.