Evolution Test Two

Front 1

Genetic Drift

Back 1

Genetic drift is a random, non-selective mechanism of evolution.

It does not lead to evolution, but it does change the allele frequencies in a population – genetic drift results from a violation of the assumption of infinite population size.

IE: ultimately the result of finite population size.

Front 2

Name 3 long-term consequences of genetic drift on populations

Back 2

1. variation increases among populations
2. higher probability that alleles are fixed or lost
3. heterozygosity is decreased

Front 3

What is the single parameter that determines the rate of genetic drift in nature?

Back 3

The rate of genetic drift is inversely related to population size.

So a small population will have a quick rate of genetic drift (towards fixation or loss of an allele).

While a large population will have a slow rate of genetic drift.

Front 4

How is the probability of fixation determined?

Back 4

The probability of fixation is determined by the allele’s initial frequency – if an allele has a high initial frequency, it will drift to fixation if genetic drift is the only evolutionary mechanism at process.

A low initial frequency will mean the allele is more likely to be lost.

Front 5

What is heterozygosity?

Back 5

Heterozygosity (the frequency of heterozygotes in a population) is lost as alleles move towards fixation or loss – so heterozygosity is lost as fast as the rate of fixation or loss.

Front 6

What were the effects of small population size on the evolutionary forces affecting of greater prairie chickens?

Back 6

The evolutionary effects acting on the chickens were GREATER since the population was SMALL and isolated. The effects of genetic drift were greater.

Front 7

How did inbreeding arise, and what were the consequences for the size of the prairie chicken population?

Back 7

Inbreeding arose due to the fact that the populations were isolated and scattered among the prairie. Because the population was small, there was reduced heterozygosity, which leads to inbreeding depression – or a reduction in fitness. In this case, decreased hatching success. This inbreeding depression decreased the population size, which then led to more genetic drift.

Front 8

Why did migration alter the fitness of the declining prairie hen populations?

Back 8

Migration altered the fitness of the populations by increasing heterozygosity and thus increasing fitness by increasing hatching success in eggs.

Front 9

Name three types of natural selection, based upon the shape of the fitness function.

Back 9

1. Stabilizing Selection
2. Disruptive Selection
3. Disruptive Selection

Front 10

Stabilizing Selection

Back 10

Occurs when intermediate phenotypes have the highest fitness. Found in newborn babies, a median weight has the highest survival rate.

Reduces phenotypic variance.

Front 11

Disruptive Selection

Back 11

Occurs when extreme phenotypes have the highest fitness. Can results in dimorphism, ie a bimodal distribution as the population mean moves away from the intermediate value. Variance increases here. EX: beak size and opening large and small seeds

Increases variance.

Front 12

Directional Selection

Back 12

Occurs when one phenotype has a higher fitness, ie a phenotype to the right or left. Changes the mean value of a trait. Variance in traits decreases as the trait to the left is moved to the right. Or vice versa. Ex: the increasing oil content in corn over 50 years.

Decreases variance

Front 13

Selection gradient

Back 13

The selection gradient measures the strength of selection.

Front 14

Selection differential

Back 14

S = Xa-Xb; it is the actual strength of phenotypic selection.

Xa = trait mean after
Xb = trait mean before

Front 15

Breeders Equation (plus variables)

Back 15

R = h2S

R = response to selection
h = heritability
S = selection differential

Front 16

What is the breeders equation

Back 16

It predicts the response to selection using heritability and the selection differential (strength of phenotypic selection). It is useful for studying the outcome of natural and artificial selection because

Front 17

What causes there to be additive genetic variance in a population (VA)?

Back 17

There is additive genetic variance in populations because there is covariance between parents and offspring. Which is to say, the offspring is a product of the parents gene pools adding together.

Front 18

Why is additive genetic variance (VA) necessary for a trait to evolve in response to natural selection?

Back 18

Additive genetic variance is necessary for a trait to evolve in response to natural selection because it combines traits which natural selection selected to survive. offspring will be suited to the environment parents were in.

Front 19

Why is the heritability of head number undefined in humans?

Back 19

because there is no variability between parents when it comes to head number.

Front 20

Math problem:

You are studying a population of warblers. You find that the average body mass in this population is 13 ounces. Following a massive period of mortality, the remaining warblers pair off and reproduce; these warblers have an average body mass of 11 ounces. Is there positive or negative directional selection operating in this population? If the heritability of body mass is 0.37, what is the expected body mass in the next generation?

Back 20

solve using eqn sheet.

Front 21

If all mutations in a codon are equally likely, is a mutation more likely to be non-synonymous or synonymous?

Back 21

Synonymous mutations are most likely to occur versus nonsynonymous mutations.

Synonymous mutations are more likely to occur because they do not reduce fitness and are often neutral, whereas nonsynonymous mutations doreduce fitness.

nonsynonymous mutations can lead to deleterious effects because nonsynonymous mutations can change the proteins ability to function.

Front 22

What two factors control the rate of nucleotide substitution?

Back 22

The probability of fixation for each new mutation and number of new mutations of each generation.

Front 23

What does the ratio of non-synonymous to synonymous substitutions (dN/dS) tell you about a gene?

Back 23

The ratio of dN/dS tells us what type of mutation the gene is undergoing.

Front 24

Purifying Selection

Back 24

Purifying selection removes deleterious amino acid sequences in proteins though natural selection.

dN/dS < 1

Replacements are deleterious

Front 25

dN/dS < 1

Back 25

Purifying Selection

Front 26

Neutral Selection

Back 26

b. Genes evolving neutrally should have equal amounts of nonsynonymous and synonymous mutations so that dN/dS =1.

Replacements are neutral

Front 27

dN/dS = 1

Back 27

Neutral Selection

Front 28

dN/dS > 1

Back 28

Positive Selection

Front 29

Positive Selection

Back 29

A minority, replacements here are advantageous.

Front 30

Why is adaptation by natural selection considered one of the triumphs of evolutionary biology?

Back 30

It is a triumph of evolutionary biology because it explains nature and how species have adapted to survive within their environments.

Front 31

Adaptation

Back 31

a trait or a suite of traits that increase the fitness of the possessor.

Front 32

What are Three reasons to test hypotheses rigorously:

Back 32

1. Differences among populations may not be adaptive – for example, traits could have been fixed through genetic drift.

2. Not every trait of an organism or every use of a trait by an organism is an adaptation. Example: panda thumbs are not actually thumbs, just a bone they can use similarly to thumbs
.
3. Not every adaptation is perfect. Example: Oxpeckers eating the blood and earwax of large mammals provides a lot of nutrients but is also a unpredictable food source.

Front 33

What are 3 approaches to testing hypotheses

Back 33

1. Observational: Used when adaptations are difficult to test experimentally. Also good for testing hypotheses which involve how organisms behave in nature. Observations are made in the natural environment, are made just by watching organisms in the environment.

2, Comparative: Compares two or more species to study the evolution of form and function of traits. Uses tests such as correlations between traits, or correlations between traits and the environment (megachiropteran bats).

3. Experimental: manipulating a variable of interest to determine how it affects fitness. Example: moth pollinating flower, tying the tube to test effect of pollination effectiveness for each flower.

Front 34

Tephritid flies wave their striped wings when confronted with jumping spiders. How did Erik Greene test whether the wing stripes, the wing waving, or both are adaptations to prevent being attacked by jumping spiders? (See text pages 367-369.)

Back 34

Tested both the markings and the waving.

Jumping spiders were more likely to retreat from flies with marked wings and wing waving.

Spiders attacked flies that lacked wing markings, wing waving, or both.

All flies were eaten by OTHER predators (other than jumping spiders), despite wing markings and wing waving.

Thus, Tephritid flies have adapted to mimic jumping spiders to avoid being eaten.

Front 35

Local adaptation

Back 35

When there are two populations with different mean trait values.

Front 36

Reciprocal Transplant

Back 36

experiments are designed to test whether or not the differences in populations are adaptive.

examples: Char fish from cold, medium, and warm lakes have varying growth and reproduction speed. For the experiment, fish from each population were grown in each different temperatures of water to test how the growth and reproductive rate were affected. Each fish had the highest fitness in their home water’s temperature.

Front 37

New Zealand Snail Parasite Recipricol Transplant Example

Back 37

New Zealand snail parasites are found on different types of snails, but are the parasites adapted to their hosts? Data showed that parasites grown on their home-site snails had higher fitness than ones grown on snails from other regions.

Front 38

Why are sex-limited extravagant traits difficult to explain by natural selection?

Back 38

Sex-limited extravagant traits are difficult to explain by natural selection because they appear to reduce fitness and benefit predators.

Front 39

Why did Darwin think that sex limited extravagant traits might be “fatal to my whole theory”?

Back 39

Darwin said that these traits would be fatal to his theory of natural selection because these traits could not have been selected for by natural selection – since they reduce fitness, and natural selection increases fitness

Front 40

Explain giraffe’s long necks using natural selection for foraging versus sexual selection for mate acquisition.

What evidence supports sexual selection? What evidence refutes natural selection?

Back 40

Natural selection: Longer necks allow giraffes to reach newer and more nutrient dense leaves on the top of trees. Advantageous because the long necks would receive more nutrients and be healthier because of it – increased fitness

Refuted by the fact that giraffes do not eat the top leaves on trees; they eat the middle leaves.

Sexual selection: Males with longer necks have a higher chance at winning in fights against males with shorter necks. So males with longer necks get more mates than short-necked males

Supported by the success of long necked males fighting v. shorter necked males.

Front 41

Sexual Selection

Back 41

Differential reproductive success due to variation among individuals in success at getting mates.

Front 42

What is the difference in the way fitness is measured under natural selection versus sexual selection?

Back 42

Female: fitness measured by the number of offspring per mating due to their limited number of eggs.

Male: Fitness measured by number of matings due to the availability of scarce eggs; the more females they reproduce with the more eggs they can fertilize.

Front 43

How does fitness differ for females v. males generally speaking?

Back 43

Females have more investment in offspring than males do, due to the fact that it takes more energy to produce an egg and raise an offspring. Females have a larger gamete and offspring investment, ie they spend more time raising offspring and they spend time incubating the egg. Males have less gamete investment (hence why they have thousands of sperm per mating event vs. few female gametes). They also typically have less parental investment.

Front 44

Give at least 3 ways in which parental investment typically differs between males and females.

Back 44

1. Females reproductive success is small and measured by the number of eggs she has .
2. Males’ have limited parental investment because their reproductive success is based on how many mating events he can be in.
3. Females are more heavily invested in the success of their offspring – they spend a lot of time gestating offspring, plus their eggs have a lot of nutrients in them. having more parental investment might increase the chances of her offspring growing up and passing on her genes.

Front 45

Why does Selection favor extravagant traits in the sex with the lowest parental investment.

Back 45

The female chooses the male with the extravagant traits because he might have the best genes, so since the male will have little parental investment she might as well get his good genes.

These extravagant displays can also include giving food/resources which benefits the female

Front 46

Batemans principle

Back 46

is when the fitness is limited by the number of mates – typically found in males. Can occur in females (pipefish females competing for males’ brood sacks).

Front 47

Bateman's Principle Graphs

Back 47

Males number of offspring increases w/ the number of mates.

Females number of offspring is consistent despite having multiple mates.

Front 48

What evidence suggests that selection should act more strongly on male rough-skinned newts?

Which trait has evolved by sexual selection in the newts?

Back 48

Selection would act more strongly on male rough-skinned newts because males males’ did not mate produced zero offspring, and the males who did mate produced 300+ offspring. So the association between the number of mates and number of offspring is strong.

A trait evolved by sexual selection in the newts is big crests – which are favored by females to mate with

Front 49

Intersexual selection

Back 49

is selection between sexes.

Front 50

intrasexual selection

Back 50

selection competition between the same sex for mate selection. Ex: peacocks.

Sperm competition in bats is an example of Intrasexual selection

Front 51

Altruism

Back 51

behavior that benefits another organisms with a sacrifice to the actors fitness.

Front 52

Kin Selection

Back 52

an individual increasing their own fitness by reproducing yourself or helping a relative reproduce.

Front 53

Inclusive Fitness

Back 53

the total fitness of an individual and is affected by the number of offspring produced by relatives and the total offspring you produce.

Front 54

Why would altruism be fatal to the theory of natural selection?

Back 54

because natural selection aims to increase an individual’s fitness while altruism appears to decrease an individual’s fitness.

Front 55

What criteria under Hamilton's rule must be met for Altruism to evolve under natural selection?

Back 55

The indirect fitness benefit to the recipients, reduced by the coefficient of relatedness, has to be greater than the fitness reduction of the actor (the altruist).

Front 56

eusociality

Back 56

a social system where generations overlap between parents and offspring, there is cooperative brood care, and there are specialized castes of nonreproductive individuals

Front 57

In tadpoles of salamanders (text pages 453-455), altruist cannibals (discriminators) do not eat their kin. In the experiment, what was the cost to this behavior? What was the benefit? Was altruism predicted to evolve under Hamilton’s rule?

Back 57

The cost to this behavior was 0

The benefit to this behavior was 2

Altruism was predicted to evolve
2(1/2)+0=1

Front 58

Why might group living favor the evolution of altruism?

Back 58

Group living would favor the evolution of altruism because it provides protection to the entire group, mating is easier because everyone is in one spot and resource sharing occurs.

Front 59

How does haplodiploidy explain extreme sex ratios in insects?

Back 59

Hapolodiploidy explains extreme sex ratios in some insects because the females are more likely to care for the female eggs because they are more related to female insects than the male insects. So there ends up being more females than males because the more females there are the higher fitness the females have because they are all so closely related.

Front 60

Consider normal bee colonies with one singly-mated queen: what sex ratio is expected?

And Why?

Back 60

3:1

Because females are in control of which eggs live and they selectively kill some of the male eggs so that there are more females. Since females have a .75 relatedness, having more sister females in the group increases their fitness. Males do not increase their fitness.

Front 61

What evidence would you cite to show that haplodiploidy is not necessary for the evolution of eusociality?

Back 61

That there are diploid organisms with normal chromosomal selection for sexes such as termites, naked mole rats, and shrimp who are eusocial.

Front 62

Which ecological factors that might favor the evolution of eusociality are shared by the eusocial mole rates, termites, shrimp and hymenoptera?

Back 62

1. Complex nests/tunnels
2. care for the young/larvae for a period of time
3. shared resource gathering
4. have a physically dominant queen