Evolution Exam 2

Front 1

Linkage disequilibrium

Back 1

Allele at one locus is non-randomly associated with allele at another locus

Hint 1

Non-random assoc. of alleles at 2 different genes in a population

Front 2

Linkage equilibrium

Back 2

Allele at one locus is independent of allele at another locus

Hint 2

Evol at one gene doesn't affect evol at another gene

Front 3

D

Back 3

coefficient of linkage disequilibrium

Front 4

D=0 if

Back 4

genes are independently sorting, because...

Hint 4

all combinations are equally frequent

Front 5

When linked genes show LD

Back 5

chromosome freqs will change from one generation to the next, moving toward linkage equilibrium

Front 6

Factors that create linkage disquilibrim
1.
2.
3.
4.
5.

Back 6

1. Selection on multilocus genotypes
2. Physical linkage
3. Genetic drift
4. Population admixture
5. Assortative mating

Front 7

What reduces LD?

Back 7

Sexual reproduction. How?

Hint 7

Meiosis, genetic recomination, outbreeding

Front 8

Usefulness of LD?

Back 8

1. Detect physical linkage
2. Map genes for trait of interest
3. Infer population history
4. Detect positive selection on genes

Front 9

LD example:

Back 9

Ashkenazim with 8-repeat locus more likely to have 84 GG disease mutation

Hint 9

Able to date disease via the rate of recombination (750-2325 years ago)

Front 10

Selective sweep

Back 10

(aka hitchhiking) neutral genetic variation linked to a positively selected mutation will also become more prevalent

Hint 10

That haplotype becomes only one in pop, resulting in large reduction in total genetic variation in that chromosome region.

Front 11

Sexual reproduction reduces LD

Back 11

via meiosis and genetic recombination

Front 12

Sexual reproduction is costly because...

Back 12

1. Cost of finding mates (time and energy)
2. Exposure to disease
3. Possible infertility
4. Two-fold cost of males

Front 13

Explain the 2-fold cost of males

Back 13

Parthenogenetic females can make 2x as many offspring

Hint 13

Draw it out.

Front 14

Why sexual selection better?

Back 14

1. Genetically unique individuals
2. Recombin. create new multilocus genotypes
3. New combinations may be more fit
4. Breakdown LD

Front 15

Muller's ratchet

Back 15

Genetic load (deleterious mutations) increases; decreases fitness

Hint 15

Sexual pop. can purge deleterious mutns. Long term benefit of sex.

Front 16

What are the short-term benefits of sexual repro?

Back 16

1. Adaptation in a heterogeneous environment
2. Some multilocus g.t.s favorable in one envt; less favorable in future envt.
3. Quick evolution for orgs locked in evol arms race.
But...

Hint 16

Sometimes sexual repro is favored by competitors (e.g. parasites favoring sexual repro in snails)

Front 17

How is LD created?
1.
2.
3.

Back 17

1. Selection. How?
2. Drift. How?
3. Migration.How?

Hint 17

1. can't predict freq of haplotype by multiplying freq of alleles
2. Finite population - fixed for A. Mutation causes A->a. Now always linked to b because occurred on same chromosome.
3. Pops start in LE. Mix pops together and observe LD.

Front 18

Compare sexual selection to natural selection

Back 18

Nat Sel: selecting more fit indivs (better at repro)

Hint 18

Sex Sel: selecting indivs better at obtaining mates

Front 19

Derived character

Back 19

evolved in response to a selective agent.

Front 20

"Everything was perfectly designed for its purpose." Viewpoint known as

Back 20

Panglossian. Held until 1960s when...

Hint 20

biologists began recognizing trade-offs.

Front 21

Antagonistic pleiotropy

Back 21

Gene that regulates more than one trait; some may be bad for fitness.

Front 22

What did the Spandrels of San Marcos analogy predict?

Back 22

Architectural consequences of the arches coming together were not intentional, just there

Hint 22

Can't assume every feature is an adaptation.

Front 23

How can we test hypotheses about adaptations?

Back 23

1. Experimentation
2. Direct observation
3. Comparative method

Hint 23

1. Involves some kind of manipulation
2. Relies on measurement making w/o interference
3. Spp. are not indepentdent data points

Front 24

Testing an adaptation example: Why do zonosemata flies wave their wings?

Back 24

To deter jumping spiders by mimicking major predator.

Front 25

Comparative method accounts for...

Back 25

phylogeny

Hint 25

Remove effects of relatedness so evaluation is more compatible with statistical methods.

Front 26

Independent contrast

Back 26

A comparative method testing mode for adaptation (example- testes size in large bat social group)

Hint 26

1. Compare sister taxa as pairs
2. Any difference btwn species must have been acquired AFTER divergence from a common ancestor
3. Slide all points (now lines) so one point meets origin of graph
4. Treat remaining points like a regular regression

Front 27

What are limits to adaptation

Back 27

trade-offs, constraints.

Front 28

What is the Darwinian Demon?

Back 28

1. Sexually mature at birth
2. Infinite offspring
3. Reproduces constantly
4. Immortal

Front 29

Why doesn't the Darwinian Demon exist?

Back 29

1. Energy-limited
2. Biological processes NOT instantaneous
3. Physiological and evolutionary TRADE-OFFS
4. Ecological context (competition, density-dependence).

Front 30

Sexual dimorphism

Back 30

Phenotypic differences
among males and females
of the same species in
secondary sexual traits.

Front 31

Sexual selection:

Back 31

Exaggerated male traits may arise because they
increase male mating success. This advantage should
be large enough to compensate for negative
effects on survival or fecundity.

Front 32

Difference between natural selection and sexual selection

Back 32

Natural
1. Variation in trait among individuals
2. Variation in trait is heritable
3. Some individuals are more successful at SURVIVING to reproduction than others
4. Reproductive success is non-random
(individuals with favorable form of trait REPRODUCE more)

Hint 32

Sexual:
1.Variation in trait among individuals (expression of trait may be restricted to 1 sex)
2. Variation in trait is heritable
3. Some individuals are more successful at OBTAINING MATINGS than others
4. Reproductive success is non-random (individuals with favorable form of trait MATE more)

Front 33

Darwin's quote about sexual vs. natural selection

Back 33

“Sexual selection depends on the success of certain individuals over others OF THE SAME SEX, in relation to the propagation of the species; while natural selection depends on the success OF BOTH SEXES, at all ages, in relation to the general conditions of life.”

Front 34

What did Trivers 1972 explain?

Back 34

Exaggerated traits mostly in males because...

Hint 34

Differences in parental investment among males and females.

Front 35

When does sexual selection occur?

Back 35

Member of one sex (usually male) compete with each other for access to mates.

Front 36

If sexual selection occurs in males, what can be expected?

Back 36

• Males limited by number of females to mate with
• Females limited by quality of mate
• Greater sexual dimorphisms
• More ornamented or brightly colored males.

Front 37

What are the consequences of sexual selection?

Back 37

1. Male-male competition
2. Female mate choice.

Front 38

Examples for each adaptation testing method:
1. Experimental
2. Direct observation
3. Independent contrast

Back 38

3. Testes size in bats

Front 39

Forms of male-male competition
1. Form I
2. Form II
3. Form III

Back 39

1. Combat
2. Sperm competition
3. Infanticide.

Front 40

Which form of male-male competition may lead to alternative mating strategies?

Back 40

Form I: Combat.
Example?

Hint 40

Sneaker males

Front 41

What does sperm competition favor in males?

Back 41

Mate guarding, large testes, copulatory plug, structures that remove other sperm.

Front 42

What are the explanations (hypotheses) of female choice?

Back 42

1. Good genes hypoth
2. Direct benefit
3. Sexy sons hypoth
4. Pre-existing sensory bias hypoth.

Front 43

Good genes hypothesis says females asses genetic fitness in males...

Back 43

If trait is costly, indicates male quality, developmental
robustness, resistance to parasites

Hint 43

e.g. long calls in frogs.

Front 44

Direct benefit hypothesis

Back 44

If males provide resources, females directly assess quality of resources

Hint 44

May translate into higher repro fitness for both sexes.

Front 45

Sexy sons

Back 45

Runaway process; preference has no genetic correlation

Hint 45

Females mate with sexy males because sons will also be sexy. Thus she will have higher repro fitness.

Front 46

Pre-existing sensory bias

Back 46

male trait exploits pre-existing sensory bias

Hint 46

e.g. male fiddler crabs build hoods over burrows - look like shelters to females. Males court from within.

Front 47

Male choice e.g. in pipefish

Back 47

Females larger and have stripes. Males are the choosy ones.

Front 48

Types of social interactions

Back 48

Cooperative
Selfish
Altruistic
Spiteful.

Front 49

Kin selection - selection applied to the family.

Back 49

Natural selection favoring the spread of alleles that increase indirect fitness.

Front 50

indirect fitness

Back 50

reproduction by relatives made possible by an individual's actions.

Front 51

Kin selection is...

Back 51

-Natural selection based on inclusive fitness
-Process by which traits are favored because of their beneficial effects on the fitness of relatives.

Front 52

Kin selection predicts...

Back 52

1. that idivs must dispense benefits more often to kin than to non-kin
2. certain behaviors to be more common among relatives: altruism, cooperation
3. selfish and aggressive behaviors to be less common among relatives.

Front 53

What is Hamilton's rule?

Back 53

Br - C > 0

Hint 53

B= benefit to recipient
C = cost to actor
r = coefficient of relatedness.

Front 54

Selection favors altruism if...

Back 54

it increases indirect fitness

Hint 54

Cost/benefit are measures in units of surviving offspring.

Front 55

Kin selection requires...

Back 55

kin recognitiion. Examples?

Hint 55

Spade footed toad morph.

Front 56

In kin selection, the allele for altruism...

Back 56

Increases by playing the odds

Hint 56

The more closely the actor is related to the beneficiary, the more likely the beneficiary also carries the altruism allele.

Front 57

Greenbeard effect

Back 57

an alternative to kin selection. Does not require discrimination among relatives

Hint 57

Allele causes carrier to grow a green beard, which is recognizable on others. Behave altruistically toward other green beards, and the greenbeard allele will spread.

Front 58

Slime mold aggregates as greenbeard example

Back 58

wild-type csA cells are suckers, make up larger portion of stalk in lab (non-reproductive), but...

Hint 58

In soil, wild-type cells are altruists toward each other, so altruistic allele higher in freq than knock-out cell.

Front 59

Eusociality

Back 59

-Indivs cooperate in caring for young
-Reproductive division of labor (sterile workers likely)
-Generations overlap.

Front 60

Why is eusociality common on hymenoptera?

Back 60

Haplodiploidy

Hint 60

Bros. and sisters only related through their mother.

Front 61

Haplodiploidy

Back 61

male haploid (develop from unfertilized eggs); females diploid

Hint 61

So sisters are 3/4 related to e/o, 1/2 to own offspring and 1/4 to brothers.

Front 62

Kin selection predicts conflict of interest

Back 62

Sisters more related to each other than brothers

Hint 62

Favors 3:1 sex ratio. Workers destroy male eggs.

Front 63

Does haplodiploidy explain eusociality?

Back 63

Problems:
-Multiple matings by queen could make workers more related to offspring than to sisters
-More than one queen may exist in a colony
-many eusocial species aren't haplodiploid (termites, naked mole-rats).

Front 64

Eusociality evolution

Back 64

Eusociality evolved in taxa that build nests and take case of young for extended periods

Hint 64

Paper wasps - workers not sterile
-but more successful when co-found nests.

Front 65

Parent-offspring conflict

Back 65

Parent related to offspring equally (r=0.5).
-Conflct btwn parent and offspring
-Indiv offspring monopolize parent
-Parent wants to maximize fitness of ALL offspring.

Front 66

Types of parent-offspring conflict

Back 66

-Weaning conflict
-Harassment
-Siblicide in boobies

Hint 66

-Mom gets more benefit by reproducing again than producing milk for current offspring
-Bee-eaters harass closely related kin (prevent from nesting) to recruit them as helpers to their parents?
-First hatchling pushes out unhatched egg; older sib kills younger in food shortage (long term)

Front 67

What is cooperation among unrelated individuals called?

Back 67

Reciprocal altruism

Front 68

What does reciprocal altruism require?

Back 68

1. Repeated interactions among same individuals
2. Many opportunities for altruism to occur
3. Indivs have good memories
4. Altruists interact in symmetrical situations.

Front 69

Life history is an organism's...

Back 69

life-time pattern of growth, differentiation, storage and reproduction.

Front 70

List some important life history traits

Back 70

Size at birth
Age at maturity
Size at maturity
Number of reproductions
Clutch size

Hint 70

Nat sel can act on any of these traits to improve fitness.

Front 71

How can LH traits evolve to maximize fitness?

Back 71

1. Higher survival through ages
2. Higher fecundity at each repro stage
3. Higher fecundity earlier in life
4. Longer repro lifespan
5. Earlier age of first repro.

Front 72

Basic problem for Darwinian Demon?

Back 72

Resource allocation in a finite world

Hint 72

-Survival, maintenance
-Growth
-Reproduction.

Front 73

Why do orgs age and die?

Back 73

Nat'l selection should oppose senescence and death, but it doesn't.

Hint 73

2 theories:
1. Rate of Living theory
2. Evolutionary theory

Front 74

Rate of living theory of aging

Back 74

Aging is caused by the accumulation of irreparable damage to cells and tissues (repl error and metabolic by-products).

Front 75

What are the predictions in the Rate of Living theory of aging?

Back 75

1. Aging rate correlated with metabolic rate
2. Species should not be able to evolve longer life spans because already selected for maximal repair

Hint 75

Data does not support the age/metabolic rate correlation.
-Lifetime energy expenditure does vary
-Possible to increase life-span with artificial selection.

Front 76

Aging due to cumulative effects of cell division?

Back 76

Cells only capable of a limited number of divisions based on telomere length

Hint 76

Jury still out on this hypothesis

Front 77

Evolutionary theory of aging

Back 77

Probability of survival and advantage of maintaining and repairing somatic tissues declines with age. Aging not due to cellular damage so much as failure to repair damage later in life.

Front 78

The Evol Theory of Again states that

Back 78

Genes that negatively affect repro or survival at later stages of life are only weakly selected against.

Hint 78

Aging is due to:
1. Deleterious mutations - mutation accumulation
2. Trade-offs between repair and reproduction.

Front 79

Genes reducing survivorship and reproduction
1. Early in life...
2. Late in life...

Back 79

1. early in life are strongly selected against
2. late in life are weakly selected against

Hint 79

e.g. DNA mismatch repair enzyme.

Front 80

Antagonistic Pleiotropy hypothesis

Back 80

a trade-off and aging relationship
-aging is caused by alleles with pleiotropic effects that are advantageous early in life and deleterious later in life

Hint 80

e.g. D. methuselah homozygotes live 35% longer BUT trade-off in that they have fewer progeny.

Front 81

Phenotypic plasticity

Back 81

When selection favors different phenotypes at different times, characters can adjust.