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Evolution, Behavior and Ecology > Evolution > Flashcards

Evolution Flashcards

1
Q

What is Mendel’s first law?

A

alleles can be dominant or recessive

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2
Q

What is Mendel’s second law?

A

assortment is independent/ alleles are transmitted independent of each other if they are on different chromosomes

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3
Q

What are Darwins 5 theories

A

Evolution occurs, species multiply, common descent, natural selection, gradualism

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4
Q

What is evolution?

A

Descent with modification. All species have a common ancestor. Evolution produces complex phenotypes and new species

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5
Q

How does evolution occur?

A

Mainly by natural selection of existing variation: the preferential survival of the organisms better adapted to their environment

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6
Q

What 3 observations does Darwin make about organisms and what was his conclusion?

A

geographic similarities, animals are anatomically similar and that animals look very similar in their embryonic stage. Conclusions - all species on Earth had a common ancestor

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7
Q

What observations does Darwin make which leads him to conclude that evolution was driven by natural selection

A

Fossils show that most species went extinct
There is survival for competition because there are excessive amounts of offspring and limited resources but still there are stable population sizes.
Humans have used artificial selection to produce variation, so species can change under selection

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8
Q

Define natural selection

A

a mechanism that results in the survival and reproductive success of individuals best adjusted to their environment and that leads to the perpetuation of genetic qualities best suited to that particular environment

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9
Q

What can we conclude if population is not in Hardy-Weinberg Equilibrium

A

We can conclude that the population is undergoing selection, migration, or assortative mating (or is not large enough, or mutation rate is very high

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10
Q

How does population size affect natural selection

A

Natural selection is more effective in large populations and the effect of genetic drift is more prominent in small populations which can cause favorable alleles to go extinct

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11
Q

What is runaway selection

A

When females prefer to mate with a showy male, resulting in her sons being showy males and the daughters preferring showy males, increasing the reproductive success of the males creating a positive feedback loop

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12
Q

Define epitasis

A

Interactions between genes (which aren’t alleles), often referencing how one gene may suppress another resulting in a change in phenotype`

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13
Q

What is genetic drift

A

It is a mechanism of evolution which, unlike natural selection, is when allele frequencies in a population fluctuate due to chance

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14
Q

What are non-sex chromosomes called?

A

Autosomes

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15
Q

What are the consequences of allele on an autosome if its not in H-W equilibrium

A

H-W equilibrium will be reached in one generation

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16
Q

Directional selection favours which individuals?

A

Those at one end of the distribution of a trait

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17
Q

Stabilizing selection favours which individuals?

A

Those near the mean of the distribution of a trait

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18
Q

Disruptive selection favours which individuals?

A

Those at both ends of the distribution of a trait

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19
Q

What is the Hardy-Weinburg Law?

A

Allele frequencies will not change across generations if there is random mating, an infinite population (or the equation would not be true),no gene flow, no selection and no mutation

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20
Q

How do you work out frequency after the selection?

A

Frequency before selection x relative fitness

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21
Q

What is the mean fitness of the adult population if the aa genotype is deleterious?

A

p^2(1)+2pq(1)+q^2(1-s) or 1−sq^2

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22
Q

How do you work out the frequency of genotype after selecton when you know the frequency before selection and the relative fitness, e.g AA

A

Original frequency x (AA’s fitness / average fitness)
or
p^2 x (1/1-sp^2)

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23
Q

When calculating relative fitness, what terms can ‘before’ frequency and ‘after’ frequency be replaced with

A 
before = observed
after = expected
24
Q

What are the benefits of sex

A

Allows for out-crossing and recombination which results in variance

25
Q

What is the Red Queen Hypothesis

A

A theory which suggest that species need to continuously evolve in order to keep up with competition. If they stop evolving, they will lose to species which do. e.g hosts need to continuously evolve in order to become resistant to a parasite, which needs to continuously evolve in order to overcome such defenses. it is used to explain why sexual selection occurs

26
Q

Explain Fischer’s evolution of stable sex ratios

A
  1. Suppose males are less common than females.
  2. A male will have higher chance of mating than a female.
  3. Parents producing more males will have higher fitness.
  4. Genes for male-producing tendencies will spread.
  5. Male births will become more common…
  6. …until we reach the 1:1 sex ratio.
  7. The same argument holds if females are substituted for males.
  8. Therefore 1:1 is the equilibrium sex ratio.
27
Q

What is an evolutionary stable strategy?

A

a strategy which if adopted by all members of a population cannot be invaded by a mutant strategy through the operation of natural selection.

28
Q

What are the to configurations in biological games

A

Monomorphorism one phenotype has taken
over the population, it was fitter than the others
and dominates.. e.g all hawks
Polymorphism: there are multiple phenotypes
in a population, all reinforcing the presence of
the others. e.g a stable ratio of hawks and dove

29
Q

What is frequency-dependent selction

A

Selection where the f fitness of a genotype depends on its frequency.

30
Q

Explain the process of frequency-dependent selection and give an example

A

When a genotype is rare, it is relatively favored by selection and it will increase in frequency; as it becomes more common, its fitness decreases and there may come a point at which it is no longer favored. At that point, the fitnesses of the different genotypes are equal and natural selection will not alter their frequencies: they are at equilibrium. The sex ratio is another case in which selection is frequency-dependent.

31
Q

What is the handicap principle and give examples

A

A theory which suggests that certain signals are costly and thus cant be bluffed, therefore they are reliable indicator of quality. Low quality specimens could not afford to give of the same standard of signal as high quality e.g an impala stotting to show off it’s quality to a predator or a bird of paradise dancing with its elaborate feathers

32
Q

Explain the process of Fishers runaway selection

A

For what ever reason some females have an underlying
preference for males with an exaggerated trait. Sons of choosy mothers have the exaggerated trait and carry
the tendency to be choosy. Daughters tend to be choosy, and carry the tendency for the exaggerated male trait. Therefore exgagerated traits (in males) and the preference for exaggerated traits (in females) will coevolve in a positive feedback [“linkage
disequilibrium”] and reinforce heach other

33
Q

What is linkage disequilibrium

A

The nonrandom association of alleles at different loci

34
Q

What are the 4 ways to answer the question why do male birds often have bright colors or long feathers?

A

Ontogeny (during development) Overtime Proximate
Phylogeny (over generations) Overtime Ultimate
Mechanism (immediate causation) Current Proximate
Adaptation (fitness function) Current Ultimate

35
Q

Is the interest of a gene always aligned with the interest of the individual

A

No

36
Q

What is intragenomic conflict

A

When selfish genetic elements distort the standard rules of inheritance to gain a transmission advantage over other parts of the genome, often at the expense of the host organism itself.

37
Q

Give an example of intragenomic conflict in nuclear genes

A

Conflict between chromosome A and B in the grasshopper Eyprepocnemis ploran. The B chromosomes cause the disintegration of the chromosomes accompanying
them in the spermatozoa, thus reducing to zero the
fitness of the host genome

38
Q

What is a b chromosome

A

It is a parasitic chromosome not necessarily present in most of the species population and are not needed for basic life functions like A chromosomes. It is transmitted in higher-than-expected frequencies, which leads to their accumulation in progenies.

39
Q

What is meiotic drive

A

When one copy of a gene is passed on to offspring more than the expected 50% of the time. It is a type of intragenomic conflict, whereby one or more loci within a genome manipulate the meiotic process in such a way as to favor the transmission of one or more alleles over another, regardless of its phenotypic expression.

40
Q

What is a segregation distorter?

A

A gene which does not follow the usual process of meiosis and is instead present in more than half of the gametes

41
Q

What happens is a segregation distorter is present on the sex chromosomes?

A

It will lead to an uneven sex-ratio, which can lead to population extinction

42
Q

What is kin selection?

A

It is a evolutionary strategy that favours the reproductive success of an organism’s relatives, even at a cost to the organism’s own survival and reproduction.

43
Q

What is inclusive fitness

A

the ability of an individual organism to pass on its genes to the next generation, taking into account the shared genes passed on by the organism’s close relatives.

44
Q

What is allopatric speciation?

A

(geographic speciation) speciation that occurs when biological populations of the same species become isolated from each other to an extent that prevents or interferes with genetic interchange.

45
Q

What is sympatric speciation

A

speciation that does not require geographical isolation to restrict gene flow, such as a population occupying different niches

46
Q

Give an example of sympatric speciation

A

Apple maggot flies used to only lay eggs on hawthorn bushes (which are native to America) and domestic apples (which were introduced to America by immigrants and bred). Females generally choose to lay their eggs on the type of fruit they grew up in, and males tend to look for mates on the type of fruit they grew up in. So hawthorn flies generally end up mating with other hawthorn flies and apple flies generally end up mating with other apple flies.

47
Q

What is allopoidy

A

speciation which occurs when two species hybridize. If the resulting hybrid offspring has an odd number of chromosomes, it wont be able to reproduce sexually

48
Q

What is a clade?

A

anorganism and all its descendants/ a branch of a phylogentic tree

49
Q

What are homologies

A

Similarities due to common descent

50
Q

Why do we get disease X (proximate/how plan)

A

Ontogeny - Developmental explanations for changes in individuals, from DNA to their current form which could have lead to the disease
Mechanism (causation) - Mechanistic explanations for how the disease formed

51
Q

What is mutation accumulation?

A

It is when harmful mutations accumulate over evolutionary time because there is no/weak selection against them due to the fact their deleterious effects only show later in life after the animal has reproduced

52
Q

What is Antagonistic Pleiotropy.

A

When one gene controls for more than one trait where at least one of these traits is beneficial to the organism’s fitness and at least one is detrimental to the organism’s fitness.

53
Q

Why do we get genetic diseases?

A
  1. Diseases may reflect our evolutionary history
  2. Intragenomic conflicts
  3. There is no selection against certain diseases
54
Q

Explain why we get genetic diseases in term of our

evolutionary history and genetic drift and give an dxample

A

Isolated populations can be victims of genetic drift which can make harmful mutations more common. Around 1775 a typhoon reduced the population of Pingelap to 20 people; one carried and allele for achromatospsia resulting in 5% of the current pop. being colourblind

55
Q

Explain how evolutionary history can affect our responses to medicine and give an example

A

Genetic variation can result in different responses to drugs. Warfarin is used to destroy blood clots, however those carrying the rs9923231 allele of the gene VKORC1 will uncontrollably bleed is given the standard dose. 100% of Hans Chinese have this allele whilst only 10% of Africans did. Strong evidence had been found to suggest that this is due to natural selection, although the cause is not clear

56
Q

What explains the differences in lifespan

observed in different species?

A

Extrinsic mortality rates affect the strength

of selection at different ages.

Evolution, Behavior and Ecology (3 decks)

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