ch 23

Question 1

outcomes of inbreeding

Answer 1

• more homozygotes w each gen
• does not cause evolution bc allele freqs do not change in population (genotype freqs do though)
• can speed rate of evolutionary change through exposure of recessive deleterious alleles
• inbreeding depression

Question 2

deleterious alleles

Answer 2

• not noticed in heterozygotes bc recessive
• inbreeding increases homozygotes so the trait is exposed to selection and often eliminated

Question 3

inbreeding depression

Answer 3

• decline in avg fitness when homozygotes increase and heterozygotes decrease
• common problem in small populations

Question 4

directional selection

Answer 4

• changes average value of a trait
• graph will shift left or right
• natural selection finds one allele most favorable
• if this selection cont. over time, all deleterious alleles will be eliminated and it will be 100% the selected allele (aka a fixed allele)

Question 5

stabilizing selection

Answer 5

• reduces variation in a trait
• reduces extremes
• graph gets narrower but stays centered

Question 6

disruptive selection

Answer 6

• increases variation in a trait
• favors extremes
• can play a role in speciation
  graph forms two hills

Question 7

balancing selection

Answer 7

• maintains variation in a trait
• no phenotype has a distinct advantage
• includes heterozygote advantage and frequency-dependent selection
• no single phenotype is favored at all times in a pop
• graph does not change at all

Question 8

purifying selection

Answer 8

• when selected allele is fixed and deleterious allele is lost

Question 9

heterozygote advantage

Answer 9

• when heterozygotes are more fit than homozygotes
• commonly observed in immune system

Question 10

frequency-dependent selection

Answer 10

• the strength of selection on a genotype varies with the frequency of the genotype
• ex: certain alleles favored when rare but not when common

Question 11

which is the only evolutionary process that results in adaptation?

Answer 11

natural selection

Question 12

point mutation

Answer 12

change in single base pair of dna

Question 13

sampling error

Answer 13

• when the allele freqs chosen of a subset of a pop (aka the sample) are different from the rest of the pop
• like flipping a coin and getting heads a bunch of times by chance

Question 14

founder effect

Answer 14

• group moves to geographic area and establishes a new pop
• if new pop small enough, then the allele freqs in the new pop will almost def be diff than in the main pop due to sampling error

Question 15

population bottleneck

Answer 15

• large population suddenly experiences a reduction in size
• can cause bottleneck effect

Question 16

genetic bottleneck

Answer 16

• sudden reduction in diversity of alleles in a pop
• genetic drift more pronounced when this happens

Question 17

gene flow

Answer 17

• movement of alleles btwn pops
• an individual leaves one pop and joins and reproduces w another
• equalizes allele frequencies btwn source pop and recipient pop
• pops tend to become more alike
• random with no respect to fitness
• movement of alleles btwn pops tends to reduce genetic diffs, impact on fitness can be better, worse, or neutral
• tends to increase genetic diversity if alleles arrive with IMMIGRATING individuals
• tends to decrease genetic diversity if alleles leave with EMIGRATING individuals

Question 19

chromosome level mutation

Answer 19

• change in number or composition of chromosomes
• could be gene duplication

Question 20

lateral/horizontal gene transfer

Answer 20

• transfer of genetic info from one species to another rather than from parent to offspring

Question 21

is mutation a significant mechanism of evolutionary change on its own?

Answer 21

• NO, very slow on own, can be signficant when combined with other evolutionary forces
• more significant in bacteria bc short gens
• however if mutation did not occur evolution would eventually stop
• still ultimate source of genetic variation