Evo Exam 2

Front 1

Bateman's Principle

Back 1

Eggs are expensive to make, sperm is cheap. Females are limited by resources; males are limited by their access to females. Consequently competition tends to be between males.

Front 2

Sexual selection

Back 2

Differential reproductive success due to variation among individuals. Theory: If there is heritable variation in a trait that affects the ability to obtain mates, then variants conducive to success will become more common over time. (According to Bateman, sexual selection will be a more potent force in the evolution of males than the evolution of females.)

Front 3

Intersexual selection

Back 3

Selection to attract a mate. Bright colors, dancing, big tail, etc. Ornamentation. There is a choice made by one sex (usually the females).

Front 4

Intrasexual selection

Back 4

The result of competition within a sex for access to mates. Fighting. Phenotypes generally include weaponry.

Front 5

Why are females choosy?

Back 5

1- Just because/sensory bias.
2- Direct benefits to offspring/female that increase fitness.
3- Fisher's Runaway Process.

Front 6

Fisher's Runaway Process

Back 6

Explains why females arbitrarily choose certain male traits.
1- Some males have a trait that allows them to survive better.
2- Most females in the population develop at least minimal "choosiness" for that trait.
3- B/c females prefer males with that trait (blue) they mate with more blue males and produce more blue males as well as more females who prefer blue males.
4- Becomes positive feedback loop.
5- At some point blue males are getting more mates, but also dieing more often.
6- Eventually blue males are so disfavored by natural selection that their net advantage goes away.

Front 7

Direct Benefits

Back 7

Reason for female choosiness that increases her (or the offspring's) fitness. Male traits in case of "direct benefits" tend to be benficial to females--not just ornamental.

Front 8

3 Ques of Quantitative Genetics

Back 8

1- How much variation assoc. with a trait is genetic?
2- To what extent can we predict offspring phenotype from their parents?
3- Can we predict how some trait will evolve (given some kind of selection acting on it)?

Front 9

Assumption of genetic variation curve

Back 9

All alleles are additive (heterozygote is exactly 1/2 way between the homozygotes or two alleles--one that increase phenotype and one that decreases phenotype.)
To get overall genetic value add together affects of all alleles. This works within a locus or across loci.

Front 10

Relationship between phenotypic, genetic, and environmental variance

Back 10

Vp = Vg + Ve

Front 11

Predicting offspring phenotype with two parents who are each 5'2" and there is not environmental variation acting.

Back 11

Ave genetic value of parents = 5'2"
Ave genetic value of offspring = 5'2"

Front 12

Do parents that are extreme (v. tall or v. short) produce offspring that are equally extreme?

Back 12

NO--as long as there is environmental variation.

Front 13

Narrow sense of heritability

Back 13

1- The extent to which we can predict offspring phenotype from parents' genotype (h squared)
h squared = 0.325 means that 32.5% of the difference from the mean gets passed on to the offspring.
2- Represented by the slope of the regression line relating the average of parental phenotypes to the average of their offsprings' phenotypes. If the slope of the line = 1, then there is no environmental variation in the population. With more environmental variation the slope gets shallower and our ability to predict what offspring look like decreases. (Environmental variation decreases h squared.)
3- h squared equals the fraction of difference between parents and the overall mean that is passed on.
4- h squared = the proportion of total phenotypic variation that comes from additive alleles.

Front 14

What causes the majority of phenotypic variation?

Back 14

Environment (The majority of phenotypic variation is environmental in origin.)

Front 15

Define S & R

Back 15

S = (the selection differential) the difference between the ave. phenotypes of breeding individuals and the overall ave. of the population

R (the response to selection) = the difference between the next generation and the current generation (on ave).

Front 16

Overtime the response to selection may reach a plateau that means

Back 16

narrow sense heritability (h squared) must decrease over time as S (selection differential) stays constant.
**Selection decreases variation (in particular additive variation--variation propels selection but is used up in the process, like gas in a tank).

Front 17

Genetic drift

Back 17

Increases genetic variation between populations while decreasing variation within populations. Drift happens more rapidly in smaller populations.

Front 18

Mutation rate from A to a

Back 18

mu (backwards y)

Front 19

Mutation rate from a to A

Back 19

nu (bubbly v)

Front 20

Which is a stronger force: mutation or selection?

Back 20

Selection tends to be stronger

Front 21

How to determine variation in a population...

Back 21

heterozygosity = expected frequency of heterozygotes (measure of variation)
homozygosity = measures lack of variation in a population
Heterozygosity decreases over time while homozygosity increases. Heterozygosity decreases faster in smaller populations.

Front 22

2 ways to become heterozygote:

Back 22

1- completely random mating (outcrossing)
2- inbreeding/selfing (finite population)

Front 23

Phylogenetically Independent Contrasts--When a correlation exists

Back 23

1- The correlation does not exist b/c of common ancestry; the trait has evolved independently in each species.
2- Hints pretty strongly at natural selection (adaptation). Lots of evidence for directionality (drift doesn't predict directionality). Can't test directly against null hypothesis of drift.

Front 24

Fixed differences

Back 24

Fixed differences are between species and represent a new mutation that has spread to fixation.

Front 25

Polymorphisms

Back 25

Differences between individuals of the same species. (Have not gone to fixation.) Polymorphisms are the opposite of fixation--variation.

Front 26

Basic facts of molecular evolution

Back 26

1- Fixations (substitutions) due to drift (rate = mu) happen much more slowly than fixations (substitutions) due to selection (rate = 4N(mu)s
2- Mutations that change the protein sequence are more likely to be under selection than those that don't.
(3- If detrimental alleles fix, it's always due to drift, not selection.)

Front 27

Synonymous Mutations

Back 27

(silent) Mutations that don't change the protein. Use as control. They show us what's happening with only drift.

Front 28

Non-synonymous Mutations

Back 28

(replacement) Mutations that change the protein.

Front 29

Pattern of non-syn to syn ratio...

Back 29

non-syn/syn = 0 then non-syn mutations are strongly selected against (no non-syn mutations in pop)
non-syn/syn = intermediate (ex: 0.003) then still selecting against non-syn mutations, but not as strongly.
non-syn/syn = higher (ex. 0.36) then either selection against the non-syn (bad) mutations is weaker OR some protein changes are actually beneficial
When ratio is 1 or above it's GREAT evidence for selection of beneficial alleles that have spread throughout the population.

Front 30

Naive prediction

Back 30

If selection for beneficial mutations has been important then the rate of substitution/fixation of protein changing mutations should be greater than the rate of fixation of non-protein changing mutations.
**This is naive because natural selection may be acting against detrimental alleles.
**With fitness reducing mutations we expect the opposite of this naive prediction.

Front 31

Selective sweep

Back 31

Positions on chromosome where beneficial mutation goes to fixation and "sweeps" away all polymorphism. Polymorphism = 0.
(Genetic hitchhiking)

Front 32

McDonald-Kreitman Test

Back 32

1- If some mutations (in particular the non-syn) are beneficial then the ratio of non-syn to syn will increase as the mutations get older (increase over time)
2- If all mutations are neutral, the non-syn/syn ration stays the same
3- If some non-syn mutations are detrimental, they drop out of population immediately--never get common enough to be detected in the population.

Front 33

McDonald-Kreitman test is powerful because

Back 33

It allows us to detect selection and provides control that allows us to distinguish between NS for beneficial changes and relaxed selection against deleterious mutations.

Front 34

3 requirements for natural selection to act

Back 34

1- Variation for a trait
2- Inheritance of that variation
3- Variation in survival or reproduction assoc. with variance in the trait

Front 35

Twelve Evolutionary Trends & Characteristics of Primates

Back 35

1- Generalized skeleton
2- Free mobility of fingers & toes
3- Replacement of claws with nails
4- Decreased olfaction
5- Increased reliance on vision
6- Reduction in number of teeth
7- Abbreviation of snout
8- Trend toward erect posture
9- Elaboration of brain
10- Increased body size
11- Prolongation of life span
12- Adaptations to single births

Front 36

Generalized Skeleton

Back 36

-hasn't changed much in 70mya (very similar to ancestors)
-double bone in limbs
-clavicle
-pentadactyly

Front 37

Free Mobility of Fingers & Toes

Back 37

-opposable thumb
-allow precision grip
-young hold onto mother 24/7 (humans only to break this except some "primitive prosimians"

Front 38

Replacement of Claws with Nails

Back 38

-improves ability to feel
-exceptions: grooming claws (prosimians, marmosets & tamarins)
-dermatoglyphics = fingerprints = ability to hold onto things (reflects importance of touch in primates) touch becomes basis of love

Front 39

Decreased Olfaction

Back 39

-loss of rhinarium (wet nose) - prosimians still have, monkeys don't
-vomeronasal system (internal & connected to amygdala (limbic system = emotion, fear, etc)- prosimians and NW have, OW, apes, us don't have
-less scent marking
-smell becomes less important as we move up the primate ladder

Front 40

Increased Reliance on Vision

Back 40

-stereoscopic vision (eyes in front, field of vision overlap = depth perception)
-color vision
-nocturnal -> diurnal (except owl monkey & tarsier, no tapetum)prosimians have
tapetum

Front 41

Owl Monkey & Tarsier - Return to Night

Back 41

no tapetum, eye shape similar to diurnal species (who see color) therefore we know ancestors of these primates was diurnal and sometime reverted to being nocturnal

Front 42

Reduction in Number of Teeth

Back 42

ancestral = 44 3-1-4-3
primitive primate = 40 2-1-4-3
NW monkey = 36 2-1-3-3
OW monkey, ape, human = 32 2-1-2-3
**grinding teeth in back are decreasing- the premolars in particular
exceptions: marmosets/tamarins 2-1-3-2
and aye-aye 1-0-0-3 (coconuts, insects)

Front 43

Abbreviation of Snout

Back 43

exception = baboon
-associated with other trends: eyes to front, scent decreased in importance so teeth must decrease b/c no room
-example of neoteny (over course of evo. time begin to look more infant-like; flat face is character of young mammal)

Front 44

Trend Toward Erect Posture

Back 44

-vertical clinging & leaping (ex: bushbaby)
-brachiation
-ischial callosities (b/c spend more time sitting, free hands to eat, etc.) **ONLY in OW monkeys, NOT NW monkeys
-bipedalism

Front 45

Anatomical Changes Needed for Bipedalism

Back 45

-heel/tripod placement of foot- chimps stand on side of foot (spread weight)
-change in angle of femur
-change in pelvis shape (more "bowl-like")
-change in curve of vertebral column (C to S shape)
-move foramen magnum forward to balance head like "lolly-pop"
**stood up first, then we became human (massive change in brain)

Front 46

Elaboration of Brain

Back 46

-hemispheric size (cortex, with exception of olfactory cortex which gets smaller)
-visual cortex (back of brain, occipital lobe)
-association and limbic areas
**chimp/ape brain 1/3 the size of ours--they're not just hairy humans)

Front 47

Increased Body Size

Back 47

-lower metabolism (BMR = 70W to the 3/4)
-hair density decreases
-sexual dimorphism increases - only contradiction is monogamy
-move into diurnal niche if greater than 1 kg prosimians, the smaller ones are nocturnal

Front 48

Prolongation of Life Span

Back 48

Lemurs: 4m pregnancy, 3-6m infancy, 1-2 @ puberty, 15yr lifespan
Monkeys: 6m pregnancy, 6-12m infancy, 3-4 @ puberty, 20-30yr lifespan
Apes: 8m pregnancy, 3-5yr infancy, 8-12 @ puberty, 40yr lifespan
Humans: 9m pregnancy, 5yr infancy, 11-14 @ puberty, 50-80yr lifespan

Front 49

Adaptations to Single Births

Back 49

-2 mammary glands
-bicornate uterus to unicornate uterus
-epitheliochorial to hemochorial placenta (more attached/invasive/bloody)
-external maternal care
-carrying infant from birth
-female sociality