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Evolutionary Biology > Final Exam > Flashcards

Final Exam Flashcards

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1
Q

What has facilitated the evolution of snake venoms?

A

Beta-defensins.

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2
Q

What constrains adaptation?

A

Laws of physics, like mechanics and energy efficiency.
Genetic and developmental correlations - selecting a trait may be limited or bring a correlated response to selection.
Pleiotropy - one gene affecting the expression of 2 or more traits!

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3
Q

What is antagonistic pleiotropy?

A

One trait improves fitness while the other reduces it.

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4
Q

What is an example of a developmental constraint?

A

The 7 cervical vertebrae in the neck - traits that expand on this may reduce fitness elsewhere or have negative effects on the body.

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5
Q

What is an example of an imperfect adaptation?

A

The nerves that connect to gill arches are retained in creatures, like giraffes, long after they have been lost. These nerves still loop around blood vessels.

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6
Q

What is an example of convergence?

A

Eutherians and marsupials looking similar. Also an example of homoplasy.

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7
Q

What is convergent evolution?

A

Independent evolution of similar traits in different lineages.

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8
Q

How is convergent evolution different from homology?

A

Homology is similarities in related lineages that reflect the same underlying trait, thus implying a SHARED evolutionary history.

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9
Q

What is parallel evolution?

A

Convergent evolution resulting from the same genes being modified in different lineages. This may reflect deep homology - which are traits that arise in different lineages from the same inherited regulatory networks.

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10
Q

What is ansiogamy?

A

Unequal sized gametes - big eggs, tiny sperm!

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11
Q

What is sex?

A

The combining and mixing of chromosomes during offspring production.

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12
Q

Asexuality and self-fertilization are both forms of…

A

Uniparental reproduction/

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13
Q

What kinds of asexuality exist?

A

Binary fission in bacteria, vegetative propogation in plants, and parthenogenesis in rotifers, aphids, and allies.

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14
Q

How to bedlloid rotifers reproduce?

A

They are almost exclusively asexual - males have never been found. Haven’t had sex in 80 million years.

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15
Q

Why sex?

A

It helps speed up the rate at which a pop can adapt and evolve. They also tend to be better adapted and persist more over the long term. Most asexual species are just short lived.

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16
Q

Why NOT sex?

A

It’s wasteful - males take up space and use resources, but contribute little to reproduction. Females invest so much but only pass off half their genes! In theory, natural selection should favor asexual females.

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17
Q

What are G.C Williams sex arguments?

A

A high cost implies a high value for sex. It may not be adaptive in low fecundity higher plants and animals. Intense competition among siblings could favor diverse genetic progeny.

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18
Q

What are J. Maynard-Smith’s sex arguments?

A

It can speed evolution, quickly and efficiently eliminate mutations, and reduces linkage disquilibrium.

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19
Q

Sex creates new genotypes, which means…

A

it reduces linkage disquilibrium. Sex can favor both mutations at the same time - without it, only one.

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20
Q

What did Crow and Kimura theorize?

A

That sex can speed up the spread of advantageous mutations in large populations.

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21
Q

What is Muller’s Ratchet?

A

A chart that shows that asexual populations will steadily accumilate more mutations over time.

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22
Q

What is Kondrashov’s Hatchet?

A

It shows genetic polarization in an asexual population - sex produces variance in fitness, which makes selection efficient.

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23
Q

What is the Red Queen hypothesis?

A

Since pests keep specializing on common genotypes, it makes sense to keep generating rare ones. “Running as fast as you can to stay in the same place” is like trying to adapt to a co-evolving pest. This makes sex very beneficial.

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24
Q

What’s up with snails in New Zealand?

A

Where there are more male snails, there is more sex where parasites are more abundant. Implies that sex can help populations adapt to coevolving parasites.

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25
Q

What is the twofold cost of sex?

A

Males themselves cannot produce offspring, so only half the population is producing young. Asexual lines have everyone producing offspring.

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26
Q

Are males just parasites?

A

Males that help females raise more young can increase the reproduction of the pair beyond what a female can raise herself.

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27
Q

Why is there such an even sex ratio?

A

If parents produced mostly daughters, there is an evolutionary advantage to produce more sons, and vice versa. Production of a sex is favored when rare.

28
Q

What is sexual selection?

A

Differential reproductive success in competition for mates. Intra-sexual is to overcome others, inter-sexual is to charm. Sexual selection is often very strong and pronounced.

29
Q

Female preference is…

A

typically consistent, like how female stalk-flies prefer longer stalks.

30
Q

What are some trade-offs for ornaments and armaments?

A

They can reduce many things.

31
Q

What drives sexual selection?

A

The strength of it is driven by the variation in reproductive success. It is often stronger on males, who have the opportunity to increase fitness by mating multiple times.

32
Q

Male-male competition can lead to….

A

extreme variance in reproductive success. Competing is costly!

33
Q

Why is male care rarer than female care?

A

Female are often “stuck” with the young due to internal fertilization. They also know which one are theirs - males may be uncertain about progeny, and because nat. selection favors parental care to one’s own progeny, its a risk.
Males may also gain more fitness by fertilizing multiple females rather than caring for young that might not be theirs.

34
Q

What is the “good genes” hypothesis?

A

The fact that bright or ornamental males signal underlying genetic quality, like good metabolism or resistance to parasites. It predicts that choosy females will produce offspring with higher survivorship than less choosy females.

35
Q

What are some benefits of female choice?

A

Direct benefits, like food, nest sites, and protection, and indirect ones, such as the genetic quality of the female’s offspring.

36
Q

Why do females mate with several males?

A

It increases genetic diversity among her progeny, obtains resources from multiple males (like how some insects eat the spermatophore rather than using it), and when she finds a “better one”.

37
Q

Why be faithful?

A

To ensure male protection, provisioning, or cooperation.

38
Q

What is monogamy?

A

One male and one female, where pair bonds form - either for life, shortterm, or otherwise. Extra-pair copulation can occur in many birds, where they appear socially monogamous but mate with several males.

39
Q

What is polygyny?

A

A male with 2+ females. Has very strong selection on the males, and the stakes are high. Seals will fight to the death for a harem. Unsurprisingly, males die at a faster rate than females.

40
Q

What are some consequences of sexual selection?

A

Lots of adornments and mating systems means faster speciation.

41
Q

What is a maturation trend in species of snakes and lizards?

A

The lower the annual mortality rate, the later reproduction tends to begin.

42
Q

How does predation affect life histories in guppies?

A

In areas of low predation, guppies live longer, wait longer, and are larger at maturity. Under predation, the opposite is true.

43
Q

Why do spontaneous miscarriages occur?

A

90% of embryos with abnormal chromosome numbers abort. It reduces maternal investment because investing in an offspring that won’t make it isn’t worth it. It also helps mitigate the cost of sex.

44
Q

Is cannibalism adaptive?

A

In sand gobys, dads eat some of the eggs to reduce the survival of those that remain in low oxygen conditions.

45
Q

What is the parent-offspring conflict?

A

Parents are equally related to all chicks, so it makes sense to play favorites with progeny that show more promise. “An heir and a spare”.

46
Q

What is genomic imprinting?

A

Gene expression silenced by methylation in one parent - offspring express the maternal or paternal copy of a gene, but never both.

47
Q

How can you postpone senescence?

A

With calorie restriction, which can slow the aging process. May involve trade-offs, such as lower fitness. Genes involved in repair can be switched out under stress.

48
Q

Why might menopause be adaptive?

A

It can help older females benefit from rearing grandchildren or current children. May also be a life-history trade off that occurs more than we know.

49
Q

What is the Trivers-Willard hypothesis?

A

Mothers can sometimes alter the sex ratio on their progeny, by way of either hormones or condition, etc. They produce more daughters when stressed out or under poor conditions, and more sons under good conditions.

50
Q

Why do fig wasps produce female-biased sex ratios?

A

Males mating with sisters is inbreeding, and a single male can inseminate multiple females, so no need to produce so many sons.

51
Q

What’s up with sex adjustment in Seychelles warblers?

A

Females are favored under high resources, because daughters helping is beneficial, and low resources harbor favored males because they will disperse from poor habitat.

52
Q

When does female preference evolve?

A

BEFORE a new male trait.

53
Q

Sperm competition increases….

A

when females mate with multiple males.

54
Q

What maximizes female fitness…

A

won’t always maximize male fitness.

55
Q

High fecundity means…

A

high mortality!

56
Q

What is the Bruce effect?

A

A pregnancy block, the tendency for female rodents to terminate their pregnancy following exposure to the scent of an unfamiliar male.

57
Q

What does natural selection optimize in light of trade-offs for life history traits?

A

The number of offspring that survive to maturity.

58
Q

Semelparity vs Iteroparity?

A

Mix of current reproduction and allocation to survive and reproduce again vs. not reproducing at all or engaging an all-out big bang reproduction, like spawning salmon.

59
Q

Why did senescence evolve?

A

2 theories - it’s a by-product of evolution, or it is adaptive and actively selected for.

60
Q

What is the biological species concept?

A

Species are groups of inter-breeding populations that are reproductively isolated from other groups.

61
Q

What is the phylogenetic species concept?

A

The smallest possible group descending from a common ancestor and recognized by unique, derived traits.

62
Q

What is sympatric speciation?

A

Reproductive isolation evolving without geographic isolation.

63
Q

What is the genetic basis of post-zygotic isolation?

A

BDM incompatibilities 0 genes that evolved within separate lineages may no longer work well together. Reflect epistatic interactions between 2+ loci.

64
Q

What is a “ring” species?

A

A population of species that can no longer interbreed. Reproductive isolation being reinforced!

65
Q

What is the origin of endemic species?

A
  • Neoendemics are ancestral species that colonize a new area then differentiate into multiple species.
  • Paleoendemics are relicts of one or more widely distributed taxa that have had contracted ranges.
66
Q

What do South America and Madagascar have in common?

A

The presence of boas.

67
Q

What is unique about Madagascar?

A

Lemurs, chameleons, many endemic birds, tenrecs, lots of frogs, plants, baobabs, palms, orchids. Has rain forests, dry deciduous forests, and stuff.

Evolutionary Biology (11 decks)

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