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BIOL 359 > Exam (new content only) > Flashcards

Exam (new content only) Flashcards

1
Q

adaptation meaning

A

a trait that increases fitness of individuals that possess it, relative to those that do not

  • a product of natural selection
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2
Q

general things to remember about adaptations (3)

A

not all variation among populations or species is adaptive

not all traits are adaptive

not all adaptations are perfect

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3
Q

Why do oxpeckers associate with large mammals?
(hypothesis, actual data/result)

A

Common hypothesis: oxpeckers eat insects and hosts are happy for them to consume parasitic ticks

Data: Oxpeckers have no impact on tick load

Oxpeckers enlarge open wounds and keep them open for longer
Oxpeckers remove wax from hosts’ ears

Oxpeckers are “vampires” and eaters of earwax; perhaps more parasitic than mutualistic

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4
Q

Why do giraffes have long necks? (why are long necks a fitness advantage, i.e. adaptation?)

(hypotheses (2))

A

Explanation 1: foraging-competition hypothesis
Giraffes competed with other species for food
Genetic variation for neck length
Those with longer necks could reach leaves competitors could not

Explanation 2: Neck-as-a-weapon hypothesis
Male necks are longer and heavier than females’
Males with longer necks were able to attract more mates

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5
Q

Methods to test Evolutionary Explanations (3)

A

Experiments
- Powerful
- Permits testing of one factor
- May be impractical

Observations
- Requires careful monitoring of study environment

Comparative method
- Test patterns in frequency of traits among species

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6
Q

What is the adaptive significance of wing markings and wing waving in the tephritid fly?
(Experimental Approach) (3 hypotheses)

A

Hypothesis 1: flies do not mimic the jumping spider

Hypothesis 2: markings mimic jumping spider, could avoid predation

Hypothesis 3: intimidate jumping spiders themselves, deter predation (CORRECT!)

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7
Q

What is the adaptive significance of nighttime resting locations of snakes? (Observational Approach)

A

best heat under medium-sized rocks

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8
Q

Why do males of some bat species have larger testes (relative to body size) than others?
(Comparative Approach)

A

Hypothesis: sperm competition

Phylogenetically independent contrasts:
When bat species evolved larger group sizes than their sister species, it also tended to evolve larger testes size relative to body size

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9
Q

phenotype plasticity (detailed)

A

Individuals of same genotype may not have same phenotype

Phenotype:
Genotype
Environment
Genotype + environment

Traits may be “plastic”
Plasticity itself is a trait that can evolve

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10
Q

limitations on adaptations (4)

A

(1) There is only so much energy to invest in traits
- E.g. female flower size in begonia
Larger flowers are selected over smaller ones but trade off (fewer larger flowers cam be produced; more may be better than fewer)

(2) There are constraints (morphological, physiological) that limit trait variation

(3) There is limited genetic variation
“Why can’t pigs fly?”

(4) There are ecological constraints
Doves and their lice (evolved very closely)

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11
Q

Questions on how to maximize fitness: (6) (sexually)

A
  1. Should it reproduce sexually or asexually?
  2. At what age should it start to reproduce?
  3. How many times should it attempt to reproduce?
  4. Should its offspring be few in number but large and high quality or large in number and small in size and low quality?
  5. Should it reproduce early in life, neglect its own maintenance and have a short life?
  6. How should individuals of the limiting sex choose among its suitors?
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12
Q

Sexual vs Asexual Reproduction

A

Asexual
- No partner required
- No gametes
- Genetically similar to parent
- Mitotic cell divisions
- Simple

Sexual
- Requires partner
- Gametes
- Offspring have genetic variation
- Gametes produced by meiosis and zygote develops by mitosis
- Takes longer & more complicated

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13
Q

parthenogenesis meaning

A

asexual reproduction where offspring develops from unfertilized eggs

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14
Q

Sexual Reproduction - 4 Advantages

A
  • Where fathers provide support for care of offspring, females can produce more offspring
  • Meiosis with crossing over (Linkage disequilibrium)
  • Mating between unrelated individuals
  • Hermaphrodites - have both male and female sex organs, capable of self fertilization
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15
Q

sexual dimorphism meaning

A

differences between males and females of a species

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16
Q

why does sexual dimorphism exist?

A

Fitness:
- Those with high fitness are those whose offspring make up a higher proportion of the next generation

Much of the variation between the sexes is explained by natural selection
- Ex. peacock’s trains - questions if it is explained by natural selection:
1. Why do the females not have the train?
2. How does it improve fitness?

Alternative explanation:
- Fitness is about survival and reproduction
Just because an individual survives to sexual maturity does not mean they will be able to convince a member of the opposite sex to mate
- Sexual selection: differential reproductive success due to variation among individuals in success at getting mates

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17
Q

Sexual selection meaning

A

differential reproductive success due to variation among individuals in success at getting mates

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18
Q

Sexual Selection vs. Natural Selection
(similarities & differences)

A

Similarities:
- For both, there must be heritable variation in trait(s) within population
- Selection operates when individuals with certain variants have more surviving offspring than others
- Selection operates among individuals of same species

Difference:
- For sexual selection, individuals compete against other members of same sex, instead of all other individuals of population, as it is for natural selection

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19
Q

Sexual Selection - Parent Investment (detailed)

A

For it to occur, it must act on the sexes differently

Driven by the difference in reproduction allocation

Males and females differ in reproductive allocation
- In addition to cost per gamete, females invest more in gamete production:
- Typically females invest 3x energy required for basal metabolism, whereas male invest 4/1000s the energy required for basal metabolism

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20
Q

Sexual Selection - Asymmetric Limits on Fitness

A

Ex. Females create 10 eggs (10 potential offspring), males create 10,000 sperm (10,000 potential offspring)

If goal is to have as many offspring as possible, then:
- Females may do this by mating once per breeding season
- Males can have more offspring with each mating

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21
Q

Sexual Selection Example: rough-skinned Newts

A
  • Males wait at a pond for females
  • Females arrive, select mate
    After mating, she lays up to 300 eggs
  • Neither parent provides parental care
  • Thus, cost of reproduction is solely the cost of making eggs and sperm
  • Therefore, females make larger investment than males (BUT pretty much all females had mates + offspring; a lot of males had no mates OR offspring)

Jones et al. caught all males and females after mating
- Induced egg laying by females in separate containers
- Genotyped all adults and a sample of eggs from each female
- Determined the number of mates and offspring for each adult in population

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22
Q

Sexual Selection - Conclusions (detailed)
what should females do? males? (optimize fitness)

A

If males are limited by access to mates, and females are limited by ability to make and rear young, then:
- Males should be competitive
- Females should be choosy
Note: in some species, access to mates is limited for females, and males invest most of energy in each offspring; in this case, female should compete and males should be choosy

Sexual Selection - Summary:
- Males COMPETE for mates
- For males, the more mating, the more fitness
Typically there are more males than receptive females
- Males compete against each other for access to females
- Females select among males
- A female does not need many matings to fertilize her eggs
- She can produce better offspring if she selects a good mate
Therefore females CHOOSE among available males for preferable one

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23
Q

How do males compete? (4)

A
  1. Combat
  2. Alternative mating strategies
  3. Sperm competition
  4. Infanticide
24
Q

bruce effect meaning

A

pregnancy termination in the presence of unfamiliar males

25
Q

Sexual Selection - Intrasexual Competition
(detailed; on the 4 ways)

A
  1. Combat
    - Males that dominate other males during COMBAT obtain access to MORE MATES
    - Leads to evolution of traits that are combat-focused e.g. antlers
  2. Alternative mating strategies
    - A “sneaky” male strategy in coho salmon (large and armoured hooknoses vs small jacks)
    - Jacks sneakily mate with females whereas large hooknoses fight each other for females
  3. Sperm competition
    - Just because a male copulates does not mean he will sire the female’s offspring (if the female has multiple mates)
    - Therefore, for species in which the females mate with MULTIPLE males, selection should FAVOUR individuals which produce more SPERM
  4. Infanticide
    - COMPETITION BEYOND CONCEPTION
    - Male lions that invade a pride will often kill the offspring of previous males so female will enter breeding condition sooner
    - In terms of fitness, male infanticide creates a conflict between new males who take over a lion pride, and its resident females
    - The females will sometimes defend their cubs, and can be killed in the process

ex: Gelada Baboons live in a social structure where one or a few males control up to 12 females and their offspring
- Males often fight to take over groups of females, and if successful, infanticide of previous male’s offspring typically follows
- Pregnant females will often ABORT pregnancy rather than investing in “doomed” offspring (BRUCE EFFECT)

26
Q

Why might females be choosy? (4)

A

Acquiring genes for her sons that will make him attractive

Acquiring genes for her offspring that confer general fitness benefits

Acquire resources

Perhaps she may prefer males that exploit preexisting sensory biases of her nervous system

27
Q

ex. red collared widowbird

A

body condition deteriorates with days since territory establishment, signalling that females’ preference for long-tailed males is logically found (they lost more body condition from territory duties, despite courting less and getting more mates)

28
Q

ex. gray tree frogs

A

females prefer long calls over short calls

29
Q

females may choose mates based on resources he has to offer, such as:

A
  • food (larger prey offered, longer copulation)
  • parental care
30
Q

Females may choose mates based on indicators of genetic quality; what is this called?

A

good genes hypothesis

31
Q

four kinds of social interactions & their effect on actor/recipient

A

mutual benefit
actor: +
recipient: +

selfishness
actor: +
recipient: -

altruism
actor: -
recipient: +

spite
actor: -
recipient: -

32
Q

why does altruism persist?

A

Hamilton’s rule

33
Q

what is Hamilton’s rule? (detailed + formula)

A
  1. An individual is rarely the sole repository of their alleles
  2. Individuals that are closely related are likely to carry alleles that are identical by descent
  3. Therefore, it is possible this behaviour could influence the probability of passing on their alleles to next generation
  4. Key parameter is relatedness of actor and recipient

Br - C > 0
B = benefit to recipient
r = relatedness of actor and recipient (measure of genetic similarity)
C = cost to actor

34
Q

how is relatedness measured?

A

Relatedness - often measured as probability that a gene copy is “identical by descent”

The probability that a gene copy sampled in an individual is identical by descent to a gene copy in another individual (i.e. Arose by replication from the same ancestral copy of an allele)

35
Q

r values examples/caculations

A

half-siblings = (1/2)(1/2) = 1/4

full siblings = (1/2)(1/2)+(1/2)(1/2) = 1/2

cousins = (1/2)(1/2)(1/2) = 1/8

36
Q

direct fitness meaning

A

an individual’s direct contribution to the next generation by reproduction (# of offspring contributed)

***Without the help of relatives!

37
Q

indirect fitness meaning

A

additional reproduction by relative that results from an actor’s actions (e.g. help)

Note: refers to additional reproduction that would NOT have been achieved without the actor’s assistance

38
Q

inclusive fitness meaning

A

direct fitness + indirect fitness

39
Q

kin selection meaning

A

natural selection leading to spread of alleles that increase indirect fitness

ex. prairie dog give alarm calls less often in the absence of kin

40
Q

parent-offspring conflict

A

Weaning conflict - towards end of nursing, mothers decrease nursing but offspring demand care
Recruitment other members as helpers

E.g. siblicide in 2 species of booby
Siblings kill one another, often while parent watches — why does parent allow this?
Food shortages may lead to death of second (later) chick anyway
- Siblicide is more likely with limited food
- Sometimes there is intervention

Note: Siblicide should occur if the individual killing the other gains enough direct fitness benefits by removing food competition to outweigh the indirect fitness costs of killing a sibling

41
Q

cooperation among non-kin

A

Reciprocity - exchange of favours among non-kin
- May be costly in short term to actor, but if favour is returned, may be greater value in long term

Example: baboons
Favours incl.: grooming and support during aggressive encounters
Individuals that had recently been groomed by someone were more likely to move towards their threat calls (presumably to their support)

42
Q

Reciprocity meaning

A

exchange of favours among non-kin

43
Q

Recirpocity is more likely to evolve under the conditions when the same individuals: (4)

A
  1. Repeatedly interact with one another
  2. Have many opportunities to return favours
  3. Sometimes need a favour and sometimes can offer a favour
  4. Have good memories
44
Q

“The tyranny of the discontinuous mind” - Dawkins, Richard

A

A critic of Dawkins argued: if species A evolves into species B, there must be a point when a child belongs to species B but parents are of species A

The Ancestor’s Tale
- Dawkin objects “to the very idea of a line: a gratuitously manufactured discontinuity in a continuous reality”

45
Q

what is a species?

A

Smallest evolutionarily independent unit
A “boundary” denoting absence of (?) gene flow among groups of individuals

46
Q

3 main species concepts

A
  1. Morphospecies concept
  2. Phylogenetic species concept
  3. Biological species concept
47
Q

Morphospecies Concept

A

Based on careful analysis of phenotypic differences in morphology

Widely applicable:
- May be used by paleontologists for identifying fossil species (but in fossils, impossible to detect differences in colour, soft tissue anatomy, behaviour, song, etc.)

Challenges:
- If criteria not carefully applied by different researchers
- For species of bacteria, archaea, and fungi (few if any measurable morphological characters)

48
Q

Phylogenetic Species Concept

A
  • Species are the smallest monophyletic groups
  • Species must have been evolutionarily independent for long enough for diagnostic traits to have evolved
  • Populations within species must have these shared derived traits

Application:
May be applied to any group of organisms (incl. - asexual and fossil species)

Challenges:
- Which traits are worth of being used to construct phylogeny
- Accepting this approach is likely to greatly increase number of recognized species

49
Q

Biological Species Concept (Mayr)

A

Based on reproductive isolation
- When individuals are unable to hybridize, or if offspring they produce are infertile
- Therefore gene flow = restricted

Widely used

Challenges:
- How does one determine whether individuals are reproductively isolated if their ranges do not overlap
- Reproductive isolation cannot be tested for fossils
- Not appropriate for asexual species

50
Q

Applications of species concepts - African Elephants

A

Traditionally, elephants classified as 2 species: African or Asian elephants
- Morphological evidence suggested that the African species might actually be 2 species: forest and savanna species
- Molecular work supported this and now we recognize 3 species!

51
Q

Application of species concepts - Bicknell’s thrush

A

First discovered by Bicknell in New York mountains
- Classified as a s subspecies of Gray-cheeked thrush

Later G.J. Wallace notes difference in size and colour between “subspecies” and species

Even later, noted differences:
- Colour of plumage
- Breeding and winter ranges non-overlapping
- Songs are distinct
- No evidence of interbreeding
- Habitat selection
- DNA evidence suggests divergence 1 mil years bp

AOU granted full species status

52
Q

Stages of Speciation (3) (list)

A
  1. Isolation
  2. Divergence in traits
  3. Reproductive isolation (in many cases, this may not occur)
53
Q

Isolation - Stage 1

A
  • Limited gene flow among populations
  • Isolation may occur due to: (a) physical separation (allopatry); or (b) genetic events (e.g. polyploidization)

Allopatry – Physical isolation may occur due to:
1. Dispersal and colonization (i.e. founder event)
2. Variance events: split a species’ distribution into 2 or more isolated ranges with minimal if any gene flow (e.g. sea level changes, lava flows, etc)

Genetic events such as polyploidization
May result in instant reproductive isolation
Because gametes of individuals of a different ploidy are incompatible

54
Q

Allopatry meaning

A

when the range of 2 populations do not overlap (as opposed to sympatry)

55
Q

Divergence - Stage 2

A

May be due to:
- Genetic drift - will have larger effect in small populations (its role as a predominant means of creating divergence has been questioned)
- Natural selection - will be most important if one of the populations are subjected to a new environment or uses new resources
- Sexual selection - if a mutation occurs in one population that causes females or males to select mates based on a different characteristic

56
Q

Reproductive Isolation - Stage 3

A

What happens if the populations come into contact with one another?

  1. Complete reproductive isolation
    If:
    - Natural selection produced adaptations for the different environments, or:
    - Genetic drift led to fixation of alleles that do not function well in heterozygous condition, or:
    - Sexual selection produced changes in mating system
    - Hybrid offspring will have lower fitness
    - Selection should favour individuals that choose mates from same population
    - Will create complete reproductive isolation
  2. Hybridization
    - Might occur if hybridization does not result in loss of fitness
    - Could result in a new species (3rd species); if the hybrid offspring occupy an environment different from either parental population
    - If fitness of hybrid offspring is equal to purebred offspring, a hybrid zone may also occur

BIOL 359 (7 decks)

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