2.6 - variation + evolution Flashcards

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1
Q

what factors produce variation between individuals

A
  • genetic
  • environmental
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2
Q

name the types of variation

A
  • continuous + discontinuous
  • heritable + non-heritable
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3
Q

what’s discontinuous variation

A
  • type of variation that can be categorised, e.g: blood group
  • characteristic can only appearing discrete values
  • influenced by one or two genes + environmental factors have little effect on
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4
Q

what’s continuous variation

A
  • type of variation that can’t be categorised, e.g: height
  • produces continuous range in which a characteristic can take any value
  • influenced by multiple genes + is often significantly affected by environmental factors
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5
Q

compare heritable + non-heritable variation

A

heritable - genetic differences between individuals
non-heritable - acquired differences in phenotypes of individuals that can’t be inherited

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6
Q

what’s evolution

A
  • change in allele frequencies in gene pool of population over time
  • occurs due to natural selection
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7
Q

how does natural selection cause change in allele frequencies over generations

A

organisms w/ advantageous characteristics are more likely to survive + pass their favourable alleles to offspring
frequency of unfavourable alleles decreases

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8
Q

what are selection pressures

A
  • environmental factors that drive evolution by natural selection + limit population sizes
  • can change frequency of alleles in population
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9
Q

give examples of selection pressures

A
  • predation
  • disease
  • competition (for food, habitats, mates)
  • environmental conditions, e.g: temperatures
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10
Q

how can allele frequencies be expressed

A

as percentage or proportion of total number of all alleles for that gene

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11
Q

state the 2 types of competition

A
  • interspecific
  • intraspecific
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12
Q

what’s interspecific competition

A

type of condition that takes place between members of different species

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13
Q

what’s intraspecific competition

A

type of competition that takes place between members of same species

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14
Q

define gene pool

A

all of the diff versions of genes (alleles) in individuals that make up a population

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15
Q

what’s genetic drift

A

variations in allele frequencies in small populations due to chance (rather than as a result of selection pressures)

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16
Q

what’s meant by the founder effect

A

when small number of individuals become isolated, forming new population w/ limited gene pool
allele frequencies not reflective of og population

17
Q

what’s the hardy-weinberg principle

A

model that allows estimation of frequency of alleles in population, as well as whether allele frequency is changing over time

18
Q

state the assumptions made by the hardy-weinberg principle

A
  • no mutations occur to create new alleles
  • no migration in/out of populations
  • no selection, alleles all equally passed on to next generation
  • random mating
  • large population
19
Q

explain the hardy-weinberg equation for calculating allele frequency

A

frequencies of each allele for characteristic must add up to 1, giving the equation: p + q = 1

p = frequency of dominant allele
q = frequency of recessive allele

20
Q

explain the hardy-weinberg equation for calculating genotype frequency

A

frequencies of each genotype for characteristic must ad up to 1, giving equation: p^2 + 2pq + q^2 = 1

p^2 = frequency of homozygous dominant
2pq = frequency of heterozygous
q^2 = frequency of homozygous recessive

21
Q

define speciation

A

formation of new species due to evolution of 2 reproductively separated populations

22
Q

why may speciation occur

A
  • genetic drift in isolated population
  • founder effect
  • natural selection
23
Q

what are the 2 types of speciation

A
  • allopatric speciation
  • sympatric speciation
24
Q

what is allopatric speciation

A

occurs when 2 populations become geographically isolated

25
Q

what is sympatric speciation

A

occurs when 2 populations within same area become reproductively isolated

26
Q

outline geographical isolation

A

physical barrer (e.g: river or mountain) separates 2 populations of the same species

27
Q

name the potential isolation mechanisms in sympatric speciation

A
  • morphological isolation
  • seasonal isolation
  • behavioural isolation
  • gametic isolation
  • hybrid sterility
  • hybrid inviability
28
Q

what’s morphological isolation

A

reproductive isolation of 2 populations due to incompatibility of reproductive systems

29
Q

what’s behavioural isolation

A

reproductive isolation of 2 populations due to differences in behaviour (e.g: diff mating rituals)

30
Q

describe seasonal isolation

A

reproductive isolation of 2 populations due to differences in their breeding seasons

31
Q

describe hybrid inviability

A
  • pos-zygote barrier
  • successful fertilisation but embryo can’t develop into living organsim
32
Q

what’s hybrid sterility

A

formation of sterile offspring from reproduction of individuals of different species

33
Q

why may reproduction of individuals of different species produce sterile offspring

A

chromosome sets from each parent differ so can’t pair up during meiosis

34
Q

give examples of a sterile hybrid + a fertile hybrid

A

sterile - mule
fertile - wheat

35
Q

what is gametic isolation

A
  • prezygotic barrier
  • successful fertilisation doesn’t occur
36
Q

what is gametic isolation

A
  • prezygotic barrier
  • successful fertilisation doesn’t occur