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BIOL10010: life's complexity > evolution > Flashcards

evolution Flashcards

1
Q

define evolution

A

cumulative change in the genetic composition of a population or species over time

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2
Q

Charles Darwins 3 major propositions for evolution

A
  1. species are not immutable
    - populations show phenotypic variation and species can change overtime
  2. descent with modification
    - related species which share common ancestor, diverge from one another gradually overtime
  3. natural selection
    - differences in phenotypes of individuals cause some of them to survive and reproduce more effectively, outcompeting them
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3
Q

what is the distinction between natural selection and evolution?

A

evolution - gradual change in the inherited traits of population over many generations

natural selection - members of population best survive to their environment and have the best chance of survival

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4
Q

define macroevolution

A

evolutionary changes among large taxonomic groups above the species level

includes the origin, diversification and extinction of species over long periods of time

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5
Q

define paraphyly

A

includes the common ancestor, but not all descendants

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6
Q

define polyphyly

A

does not include the common ancestor

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7
Q

define monophyly

A

includes the common ancestor and all descendants

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8
Q

define convergent evolution

A

organisms which are not related that have similar bodies due to evolving independently from one another

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9
Q

compare germ line and somatic mutations

A

germ line
- affects gametes
- mutations transmitted via sex
- create new alleles - heritable

somatic
- affects all daughter cells of a single cell
- not heritable

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10
Q

define population

A

a group of individuals that share genetic information

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11
Q

define gene pool

A

sum of genetic information that is carried in the population

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12
Q

define genetic drift

A

the change in frequency of an existing gene variant in the population due to random chance

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13
Q

influence of genetic drift on large and small populations

A

removes variation

genetic drift is a weak force in large populations

on small populations drift is very influential as there is less variety of genetic information

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14
Q

compare macroevolution and microevolution

A

macroevolution -
AMONG species over long time periods

microevolution -
WITHIN species that can be observed directly acting upon natural populations

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15
Q

is it true that gene flow always requires migration?

A

no, birds can distribute their gametes through plant pollen to different populations

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16
Q

2 key parameters that is needed to estimate the impact of gene flow between two populations

A
  1. genetic difference between populations
  2. level of migration, movement of hybridisation
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17
Q

define non random mating

A

A mating system in which at least some individuals are more or less likely to mate with individuals of a particular genotype than with individuals of other genotypes.

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18
Q

how does recombination contribute to evolution?

A

by creating combinations of genes that nature selects

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19
Q

how does evolution relate to mutations?

A

as DNA encodes, it must also be replicated so that daughter cells receive the same amount of DNA

however, replication is not always accurate

mutations can be introduced by DNA damage
- exogenous sources eg. UV radiation, chemical ‘mutagens’
- endogenous sources eg. hydrolysis, endonucleases
- enzymes repair of DNA but not being replaced with the correct nucleotide

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20
Q

types of mutations

A
  • point (substitution)
  • insertion/deletion
  • frameshift
  • gene duplication
  • chromosome fusion
  • somatic/germline
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21
Q

What is the Hardy-Weinberg theorem

A

this theorem dictates that allele frequencies will be in equilibrium from each passing generation when free of the effects of agents of change

22
Q

allele frequencies remain in equilibrium if five unrealistic conditions are met

A
  1. no migration - does not allow for gene flow
  2. no mutation - does not allow for changes in alleles
  3. equal fitness - no selection
  4. random mating
  5. infinite population size - genetic drift is in its weakest force
23
Q

what happens when expected frequencies do not match the observed frequencies

A

this means that the genotypes are not in HW equilibrium - and indicates a population is under the influence of the agents of change

24
Q

define allele

A

alternate forms of a DNA sequence

25
Q

define genotype

A

allelic composition of an individual or cell

26
Q

define speciation

A

evolutionary process by which new species arise through reproductive isolation causing one evolutionary lineage to split into 2 or more lineages

27
Q

sympatric speciation

A

ancestral population is divided without geographical barriers

28
Q

allopatric speciation

A

ancestral population is divided by a physical barrier

29
Q

if the genetics of speciation involves heritable changes accumulating, how does mutation, genetic drift and selection promote speciation?

A

new alleles becomes fixed and chromosomal rearrangement

30
Q

define pre-zygotic reproductive isolation

A

barriers to reproduction act BEFORE the onion of the nuclei of the two gametes

  • geographical isolation
  • mechanical
  • behavioural isolation
  • mating time differences
  • ecological differences
31
Q

define post-zygotic reproductive isolation

how does this maintain species boundaries

A

barriers to reproduction act AFTER the onion of the nuclei of the two gametes

  • fertilised offspring inviable

dampens gene flow between diverging populations

32
Q

define biological species concept

A

defines species as groups of actually or potentially interbreeding natural populations and produce natural offspring

33
Q

define adaptive introgression

A

inheritance of beneficial variation from related species that accelerate adaptation to or survival in new environments

34
Q

define balancing selection

A

maintains genetic variation in population
1. negative frequency dependent selection
2. heterozygous advantage

35
Q

how does frequency-dependent selection maintain genetic variation

A

occurs when rare phenotypes have more fitness than common phenotypes

when a genotype becomes more common, its fitness declines and different, rare genotypes are favoured

36
Q

define heterozygous advantage

how does this maintain variation in a population

A

occurs when selection favours heterozygous individuals over homozygotes

as the heterozygotes are more likely to survive, natural selection maintains both alleles in the population

37
Q

define fitness

A

reproductive and survival success an organism is in their environment

38
Q

define relative fitness (w)

A

the success of a genotype

standardised by the success of other genotypes in the population, w=1.0

39
Q

define sexual selection

A

Natural selection arising through preference of one sex for certain characteristics in individuals of the other sex

40
Q

define intersexual selection

A

mate choice
- non-random mating
- one sec preferences on specific trait in mates
- as costly to bear, honest signals of mate quality
- traits will become exaggerated until balanced by selection

41
Q

define intrasexual selection

A

male conflict
- intrasexual selection
- same sex compete
- displays strength, physical combat
- evolution + exaggeration of aramaments costly to bear

42
Q

how does sexual selection and natural selection act as opposing forces

A

sexual selection contributes to genetic variation among the offspring through traits which are costly to bear, some even being deleterious to the organism, and natural selection can act on these by balancing these traits out again - through selective the fittest survivors

43
Q

define coevolution + why can it occur

A

process when two or more interacting species affect each other’s evolution through natural selection -> back/forth affect

this occurs as each species exerts a selective pressure on each other
leads to a continuous cycle of adaptations and counter-adaptations driving force in the evolution of species interactions shaping behaviours, physiology and ecological relationships

44
Q

what is the red-queen hypothesis

A

species must constantly adapt and evolve in order to survive

45
Q

antagonistic and mutualistic interactions

A

both are subjected to coevolution between species

antagonistic
- between species where at least one party is negatively affected

mutualistic
- relationships between two different species benefit and enhance each other’s fitness, growth or survival

46
Q

why are nucleic acids useful information sources for creating phylogenies in diverse species?

A

they have many characters and occur in all biological entities

47
Q

define parsimony

A

the most simple explanation and requires the fewest steps

48
Q

how do molecular clocks “tick”

A
  • genetic mutations
  • rate of mutations
  • comparing sequences calibration
  • estimation of divergence time
  • by seeing changes in nucleotides
49
Q

define adaptive phenotype

A

provides a mechanism for organisms to regulate trait expression within their lifetime

50
Q

what are some evolutionary consequences of transposable elements?

A
  • regulation of gene expression
  • increased recombination rate
  • unequal crossover
51
Q

how does ‘population structure’ arise?

A

arises when demographic processes produce differences in allele frequencies between subsets of a larger population

BIOL10010: life's complexity (4 decks)

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