Test 2

Question 1

if individuals of a particular phenotype survive and/or produce more offspring than others: (2)

Answer 1

• phenotype must be a product of the genotype (i.e. heritable)
• genotype vary in their fitness

Question 2

rate of change

Answer 2

a function of selection intensity

Question 3

fixation meaning

Answer 3

only allele in 100% of population

Question 4

changes in genotype frequency (allele frequencies have not changed but genotype frequencies have); what could reset the genotypes back to start?

Answer 4

1 generation of random mating

Question 5

patterns of selection (4):

Answer 5

1. recessive vs dominant alleles
2. heterozygotes favoured
3. homozygotes favoured
4. frequency-dependent selection

Question 6

patterns of selection: (1) recessive vs dominant alleles

Answer 6

individuals with +/+ or +/- are normal, -/- do not survive (recessive lethal)

Question 7

patterns of selection: (1) recessive vs dominant alleles:

selection is rapid/slower when a recessive allele is ___(2) and lethal

Answer 7

selection is rapid when a recessive allele is common and lethal

selection is slower when a recessive allele is rare and lethal

Question 8

patterns of selection: (2) heterozygotes favoued

Answer 8

heterozygote advantage/superiority: the fitness of heterozygotes is greater than any homozygote
(the equilibrium point depends on selection pressure)

Question 9

patterns of selection: (3) homozygotes favoured

Answer 9

heterozygote inferiority/underdominance - the fitness of heterozygote < fitness of either homozygote

Question 10

patterns of selection: (4) frequency-dependent selection

Answer 10

ex. red/yellow orchids (after pollinator is fooled, they try to switch between flow colour to look for nectar); if small % of population, that colour’s pollen will be picked up more!

higher reproductive success if lower frequency in colour

Question 11

inbred stock meaning

Answer 11

starting stock that were all genetically identical to each other (i.e. no genetic variation)

Question 12

mutation-selection balance

Answer 12

• many mutations are deleterious
• selection may remove deleterious alleles but mutations may re-introduce them, hence they persist
• mutation-selection balance = rate of new copies of a deleterious allele produced by mutation EQUALS rate of selection removing them

Question 13

gene flow (migration) may be caused by:

Answer 13

• dispersal - one-way movement of a juvenile individual away from place of birth
• transport of pollen, seeds, spores by any means

Question 14

what does gene flow tend to do?

Answer 14

• it tends to homogenize allele frequencies among populations
• tends to prevent evolutionary divergence of populations
• may function to decrease the population-level impact of natural selection and/or other mechanisms of evolution

-> if populations all exchange at an equal rate, eventually each population will on an equilibrium frequency of alleles (w/o other evolutionary forces)
-> would equal avg allele frequencies of the populations

Question 15

Fst meaning?

Answer 15

a measure of variation among populations in allele frequencies at a locus
- “fixation index”

Question 16

Fst value range, can be computed for how many populations, what does it decrease with?

Answer 16

range: 0-1
0 = all populations have identical allele frequencies
1 = no alleles are shared among populations

can be computed for 2 or more populations

gene flow reduces Fst among populations

Question 17

evolution: (4) by genetic drift

Answer 17

• random changes in allele frequencies from one generation to the next (sampling error)
• does not lead to adaptation

Question 18

what can genetic drift lead to? (2)

Answer 18

1. fixation
2. decline in heterozygosity

Question 19

effective population size meaning

Answer 19

• ideal theoretical population size that would lose heterozygosity at the same rate as the actual (census) population size (assume everyone breeds)
• almost always lower than the actual
• WHY: not everyone in population breed

Question 20

what is the probability of fixation of one allele or another?

Answer 20

depends on starting frequency
- A=0.6, B=0.4;
- probability that drift will fix A is 0.6, and B is 0.4

Question 21

demographic events that can cause genetic drift: (2)

Answer 21

1. founder events
2. bottleneck

Question 22

found event meaning

Answer 22

occur when a population is founded by a small group of individuals
- may considered a form of genetic drift

Question 23

bottleneck meaning

Answer 23

a sharp decline in population size followed by population recovery

Question 24

H-W assumes random mating (panmictic) includes (4)

Answer 24

1. inbreeding
2. outbreeding
3. positive assortative mating
4. negative assortative mating

• does not on its own change allele frequencies
• does impact genotype frequencies, so in conjunction with natural selection, can have important evolutionary consequences

Question 25

inbreeding

Answer 25

mating among closely related individuals - results in increase in homozygotes (relative to expected H-W) - impacts genotype frequencies, not allele frequencies (on its own, non-random mating is NOT a mechanism of evolution)

Question 26

inbreeding depression

Answer 26

reduction in avg fitness due to inbreeding - results from: (1) exposure of recessive deleterious alleles to selection; and/or (2) loss of genome-wide heterozygosity (loss of heterozygote advantage)

Question 27

inbreeding is not a mechanism of evolution on its own, but:

Answer 27

- does alter genotype frequencies - alters frequency of phenotypes ina population and the pattern of natural selection - therefore, in conjunction with natural selection, DOES cause evolution

Question 28

outbreeding meaning

Answer 28

mating among highly unrelated individuals

Question 29

positive assortative mating meaning

Answer 29

between individuals similar phenotypes

Question 30

negative assortative mating meaning

Answer 30

between individuals with dissimilar phenotypes (big people with small people)

Question 31

review of agents of evolution (5)

Answer 31

selection - can change allele and genotype frequencies mutation - provides variation gene flow "migration" - when source and recipient populations differ in allele frequencies, migration can cause recipient population to evolve (tends to homogenize) genetic drift - random shift in allele and genotype frequencies non-random mating - does not change allele frequencies, but does change genotype frequencies (can affect evolution with natural selection)

Question 32

phylogenetics meaning

Answer 32

study of ancestor-descendant relationships; objective is construct phylogenies

Question 33

phylogeny meaning

Answer 33

a hypothesis of ancestor-descendent relationships

Question 34

phylogenetic tree meaning, AKA

Answer 34

AKA evolutionary tree - a graphical summary of a phylogeny

Question 35

polytomy meaning

Answer 35

3 or more subtrees; indicates genetic uncertainty as to which two are more related, thereby creating a 3+ branch node

Question 36

plesiomorphy meaning

Answer 36

refers to ancestral character state

Question 37

apomorphy meaning

Answer 37

a character state different than ancestral state, DERIVED STATE

Question 38

synapomorphy meaning

Answer 38

a derived character state (apomorphy) that is shared by two or more taxa due to inheritance from a common ancestor: these character states are phylogenetically informative using the parsimony or cladistic criterion

Question 39

autapomorphy meaning

Answer 39

a uniquely derived character state (not shared by 2 or more taxa)

Question 40

monophyletic group meaning, AKA

Answer 40

AKA clades - consists of an ancestor and all of its descendants

Question 41

paraphyletic group meaning

Answer 41

consists of a common ancestor and some, but not all the descendants

Question 42

polyphyletic group meaning

Answer 42

consists of some of the descendants of a common ancestor, but not all + exclude common ancestor

Question 43

homologous vs homoplasy

Answer 43

- homologous character states are inherited from a common ancestor - homoplasy describe similarity of character state due to independent evolution

Question 44

parallel evolution meaning

Answer 44

independent evolution of same feature from same ancestral condition

Question 45

convergent evolution meaning

Answer 45

independent evolution of same feature from different ancestral condition

Question 46

secondary loss meaning

Answer 46

reversion to ancestral condition

Question 47

outgroup - fairly closely related to ingroup - character state possessed by outgroup is defined a ____ as ancestral (plesiomorphic)

Answer 47

priori

Question 48

parsimony meaning

Answer 48

simplest scientific explanation to fit evidence is preferred (fewest steps needed to reach end evolutionary result)

Question 49

homologous characters (synapomorphies) may be used ___________

Answer 49

to construct phylogenetic trees and identify monophyletic groups - synapomorphies are phylogenetically informative

Question 50

molecular clock meaning

Answer 50

some types of DNA sequences change in a regular "clock-like" fashion - neutral changes (not deleterious/beneficial), not under selection, should accumulate in populations at a rate equal to the mutation rate - if mutation & generation time stay reasonably constant, #neutral molecular differences between 2 taxa should be proportional to age of their most recent common ancestor