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BIOL10010 Introductory Biology: Life's Complexity > 02. WHAT IS EVOLUTION? > Flashcards

02. WHAT IS EVOLUTION? Flashcards

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1
Q

When does adaptation occur?

A
  • environ change
  • genetic variation advantages some indiv
  • species survives long enough to reprod → pass on advantagous alleles
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2
Q

In what ways can a population vary?

A
  • size
  • distribution
  • structure

⇒ det influ on evol processes

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3
Q

Define adaptation

A
  • bio mechanism by which orgs adjust to environ changes.
  • an inherited aspect of an indiv that enables it to outcompete others in specific environ. evolved thru NSe.g. Galapagos finches - diff beak sizes/shape dep on food source in environ
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4
Q

Define evolution

A

cumulative change in a pop/species over time

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5
Q

Define natural selection

A
  • key agent of change that can cause evolution, whereby phenotypic variety w/in pop cause some indiv to survive + reprod + pass on advantageous alleles
    • e.g. Galapagos turtles - long necked turtles
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6
Q

Define inheritance

A

when DNA/trait passed from parent → offspring during reprod

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7
Q

Key details about Galapagos islands

A

sml series of islands w range of ages → diverse ecosystems across islands → high biodiv → 5 types/13 species finches w/ variety beak shapes/sized = adapted to diff food sources

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8
Q

Define micro and macroevolution

A
  • macroevolution: cumulative changes that occur in lg taxonomic grps over long time period - occur at or above species level e.g. emerence of new evol lineages/species
  • microevolution: ‘agents of change’ that shape species’ genome
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9
Q

Define species

A

broadly defined as grps of similar orgs that a) share genetic info and b) interbreed to prod viable offspring

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10
Q

Outline the five ‘agents of change’

A
  • natural selection: survival + reprod of the fittest
  • mutation: primary source of genetic variety
  • sexual reproduction: mating systems + recombo of genes
  • genetic drift: random changes to allele freq based purely on chance
  • gene flow: migration, movement, hybridisation
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11
Q

Defining features of populations

A
  • grp of orgs that either interact + share genetic info OR are identical
  • interaction = same place/time
  • share genetic info = interbreed to prod viable offspring
  • identical ⇒ reprod asexually - may also share genetic info
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12
Q

How does the gene pool of a population relate to evolution?

A

size of GP det evol impact
- sml GP = low genetic div = inc likelihood of allele fixation bc inc chance of GD
- lg GP = high genetic div = low chance of extinction (opp for selection) + inc chance mutation

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13
Q

How does population density relate to evolution?

A
  • density of indiv from pop in specific area - LOCATION
  • impact evol bc influ gene flow
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14
Q

How does population structure relate to evolution?

A

physical composition + social organisation of orgs det by mating systems (driver of evol bc sexual selection)

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15
Q

Steps in HWE analysis

A

Image 2

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16
Q

Conditions for HWE

A
  1. no mig
  2. no mutation
  3. equal fitness i.e. X selection
  4. infinite pop size
  5. random mating
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17
Q

Define polygenic

A

when specific phenotype is cumulative result of multi genes

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18
Q

What is the purpose of HWE?

A

provides allelic freq expected if X AoC acting on pop. we compare this info to observed allelic freq to deduce if pop = under influ of AoC-> predict evol

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19
Q

Under HWE, allele frequencies…

A

do not change over time

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20
Q

What is the d.o.f for allelic data?

A

1

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21
Q

What does it mean if a population’s allele Chi square is signficant?

A

Pop is out of HWE → likely under influ of AoC
- mig may be occuring
- mutation may have unexpected impact
- fitness costs + benefits may vary
- pop size may be sml
- mating may X be random

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22
Q

List the 3 ‘ingredients’ for NS to occur:

A
  1. variation - pop comprised of indiv w diff in appearance/behaviour/physiology e.g. fur colour, beak length, wing pattern etc.
  2. heredity - phenotypuc traits passed down from parents to offspring
  3. selection pressure - some phenotypes must offer better chance at survival long enough to reprod + pass down advantageous traits
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23
Q

Selection acts on _ alleles faster than _ alleles.

Dominant alleles are _ fixed but recession alleles…

A
  1. dom / rec
  2. never / can be fixed (never fade from pop)
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24
Q

Outline the different types of NS

A
  • directional/positive - favours indiv on one end
  • stabilising - favours indiv in middle
  • disruptive - favours indiv on opp ends (often drives speciation) e.g. specialised feeding - sml fish eat algae + lg fish eat insects
  • artifical - result of human activity - esp. common in crop selection e.g. corn, brassica
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25
Q

Balancing selection favours…

A

heterzygotes → maintain heterozygosity in pop e.g. sickle cell disease

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26
Q

How to calculate relative fitness

A
  1. Div O by E to find O:E ratio
  2. Div each O:E ratio by highest O:E ratio
  3. Div W of most fit (w=1.000) by w of next fittest to find selective adv
    e.g. 1.000/0.894=0.118→ 11.8% more fit
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27
Q

What was the impact of NS on Galapagos finches?

A

variation in beak size
heredity of beak size alleles
selection pressure due to 1977 drought

→ pos selection for inc beak size

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28
Q

What was the impact of NS on rock pocket mice?

A

variation in coat colour
heredity of coat colour alleles
selection pressure from predators in pale sandstone & dark volcanic rock environs
→ impact coat colour of pop (black mice in dark volcanic rock area + white mice in pale sandstone area)

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29
Q

Why do mutations occur?

A

damage/misreading of DNA seq → change to DNA code

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30
Q

Why are mutations called the ‘source of variation’?

A

mutations → change DNA code → intro variation into pop

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31
Q

The impact of mutation depends on…

A
  • size + location in genome
    • regulatory region → impact gene EXPRESSION to varying deg
    • coding region → impact gene FUNCTION to varying deg
32
Q

Smaller vs larger types of mutation

A
  • smaller changes
    • substitution
    • indel
    • frameshift
  • larger changes
    • duplication/inversion
    • aneuploidy
    • entire genomes/chromosome duplicated
33
Q

Outline the two broader types of mutation

A
  • somatic - transmitted via asex reprod → affects all daughter cells of parent cell
  • germline - transmitted via sex reprod → affects gametes (egg/sperm)
34
Q

How do mutations impact evolutionary processes?

A
  • mutations can impact gene pool of pop over time → minor changes to allele, under selection pressure, can sig impact phenotypic expression of pop over time

e.g. small change ⇒ sickle cell anaemia (point mutation) + teosinte to corn (point mutation) OR lg change ⇒ down syndrome (aneuploidy) + crop domestication (whole genome duplication event)

35
Q

Compare sexual and asexual modes of genetic info transfer

A
  • asex reprod
    • fission, fragmentation, budding, vegetative reprod
    • prod clones
    • no change to allelic composition
  • sex reprod
    • recombo via meiosis
    • sperm + egg
    • prod novel offspring
    • changes to allelic composition
    • can occur thru union of 2 sep orgs (typically male + fem) OR same org (hermaphrodites)
36
Q

Explain why sexual reproduction is evolutionarily advantageous

A
  • combo beneficial alleles → generate novel genotypes → ‘faster’ evolution under selection → able to adapt to new/changing environ better i.e. genetic variation = beneficial for species survival
37
Q

Explain why asexual reproduction is evolutionarily advantageous

A
  • reprod faster
  • lower E req bc X need to search for mate
  • X risk STIs
38
Q

What is random mating?

A

prob that two indiv in a pop mate is same for all poss pairs of indiv w/in that pop

39
Q

Compare assortive and disassortive mating

A
  • assortive (pos assortive) mating
    • mate w indiv w same alleles = ‘like w like’
    • X change to allele freq
    • genotypic iso → phenotypic iso → w selection can cause speciation
    • e.g. Olivella biplicata - lg animals live further up shoreline than smler animals → mate w similar size orgs
    • e.g. primates
  • disassortive (neg assortive) mating
    • mate w indiv w diff alleles - opp attract
    • outcome = novel genotypes → maintains genotypic variation w/in pop
    • e.g. wolves
40
Q

Describe mating behaviours in primates

A
  • outcome: genotypic dilution
    • promiscuity
  • outcome: genotypic differentiation
    • monogamy
    • polyandry
    • polygyny
41
Q

Describe inbreeding/self-fertilisation

A
  • outcome: inc homozygosity in all loci of genome → problematic bc delet recessive alleles may become more dom in pop
  • problem for hermaphroditic plants
42
Q

Define genetic drift

A

random + directionless changes in allele freq w/in pop

occurs due to ‘sampling errors’

43
Q

How does population size relate to genetic drift and evolution?

A

sml pop size → inc prob of GD bc less alleles to choose from → sml events have proportionally greater impact on pop than in lg pops

44
Q

Outline two types of events that reduce genetic diversity

A
  • bottleneck event = drastic reduce pop size → dec genetic div → inc prob GD bc less alleles to choose from → inc chance allelic fixation/change to allele freq
  • founder event = sml grp moves away → dec genetic div → inc prob GD bc less alleles to choose from → poss speciation over time if selection pressure bc iso from parent pop
45
Q

What are the long-term impacts of a genetic bottleneck?

A

pop # may recover but genetic div may be lost forever

→ allele fixation

→ inc homozygozity

e.g. cheetah

46
Q

Do populations need to be infinite in size for allelic frequencies to obey HWE?

A

no - they just need to be lg enough that random sampling errors X sig impact allelic freq

47
Q

Provide two examples of how small mutations can have a significant impact

A
  1. sickle cell anaemia (point mutation)
  2. teosinte to corn (point mutation)
48
Q

Provide two examples of how large mutations can have a significant impact

A
  1. down syndrome (aneuploidy)
  2. crop domestication (whole genome duplication event)
49
Q

Define gene flow

A

transfer of genetic info from one pop to another

can intro new alleles

occurs via mig, mvmt or hybridisation

50
Q

What is the difference between migration and movement?

A

mig = long dist bw distinct pops vs mvmt = intermingling of sub-pops

51
Q

For gene flow to occur, individuals…

A

must be able to interbreed to prod viable offspring

t/f mating systems influ amt/pattern of GF

52
Q

More porous geographic barriers correlate with…

A

higher connectivity

53
Q

Connectivity…

A
  • influences GF - geog barriers
  • dynamic - season/weather dep e.g. river dries up
54
Q

Define genetic hybridisation

A

interbreeding of indiv of diff spp to prod viable offspring

55
Q

Equation for change in populational allelic composition due to migration

A

Δp=m(x-p)

m = mig rate

x = freq of allele in migrants

p = freq of allele in residents

56
Q

Define speciation

A

evol process where new spp emerges due to reprod iso (LT inhibited GF)

one evol lineage split into 2+

57
Q

Outline the three types of reproductive barriers that drive speciation

A

i.e. LT inhibited GF

  • pre-mating iso
    • geog iso
    • behavioural iso e.g. mating calls
      → mutation, selection, GD
  • pre-zygotic iso
    • mating time diff e.g. coral spawn
    • eco diffs e.g. diff plants attract diff pollinators
  • post-zygotic iso
    • fertilised egg/offspring = X viable/sterile e.g. leopard frog x wood frog
58
Q

What type of reproductive barriers result in allopatric speciation?

A

pre-mating

59
Q

What types of reproductive barriers result in sympatric speciation?

A

pre-zyg
post-zyg

60
Q

What is special about elk and deer speciation?

A

allopatric distrib - elk in Nth Am + deer in Eur/Asia

GF ended 9000yrs ago but can interbreed to prod viable offspring - diff spp???

61
Q

Species boundary can be semi-permeable because…

A

occasionally hybrid offspring ≠ infertile

62
Q

Define adaptive introgression in the context of hybridisation

A

intro beneficial traits from one spp into another

e.g. Müllerian (??) mimicry in butterflies - all diff spp but same wing pattern to convince pred they are toxic

63
Q

Define introgression

A

mvmt of alleles from one spp/pop to another

64
Q

Modern humans’ DNA may contain Neanderthal DNA because…

A

hybrid + introgression

65
Q

Molecular genetics involves…

A

sequencing + analysing specific genes → understand function

66
Q

Molecular genomics involves…

A

sequencing and analysing entire genomes

→ ID regions under selection/resp for phenotypes

67
Q

Genomic analysis involves…

A
  • collecting samples/recording phenotypes
  • creating libraries + sequencing
  • investig gene loci/entire genome
  • ID SNPs + other areas of genetic variation
68
Q

Example of a phenotype with continuous distribution

A

height

also e.g. of human polymorphism

69
Q

Genome sequencing enhances…

A

our understanding of micro and macroevol e.g.

70
Q

What is a Genome Wide Association Study (GWAS)?

A

process of assoc genotypes w measurable phenotypes

71
Q

Types of GWASs

A
  • med research
    • e.g. case vs control analysis
  • evol bio
    • understanding adaptations
  • agri
    • traits of econ value
    • disaster resilience
72
Q

What is a selective sweep?

A

strong pos directional selection in specific locus of genome

e.g. lactase persistence in Eur + Afr (Tischkoff et al, 2007)

→ removes pop variation i.e. dec genetic div

73
Q

Lactase persistence in Europe and Africa is an example of…

A

convergent evol bc same gene selected on after 2 diff mutation events, resulting in same phenotype

74
Q

How does a reduction in population size result in reduced genetic diversity?

A

dec pop size → dec # indiv reprod → dec gene pool → dec genetic div

75
Q

Genetic bottlenecks impact allelic frequency…

A

randomly

76
Q

Random mating means…

A

pop structure absent + mating occurs in prop w genotype freqs

77
Q

Insignificant p-value when 1df

A

p>0.5

BIOL10010 Introductory Biology: Life's Complexity (8 decks)

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