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LEC 141 - Evolutionary Biology > Week 3 > Flashcards

Week 3 Flashcards

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1
Q

Evolution requires changes in allele and genotype frequency (micro evolution)

What forces effect such changes?

A

Mutation

Gene flow

Genetic drift

Natural selection

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2
Q

Mutation (evolution)

A

Changes in DNA

More important if occurs in cells that produce gamete’s

Current organism likely to be well adapted to environment - therefore more likely to be detrimental than beneficial (but doesn’t always have an effect)

Generally low rates (1/100,000 genes per generation) small effects on large populations

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3
Q

Examples of evolutionary mutations

A

Almond seeds from wild species contain amygdalin which is fatal (to humans) - single gene mutation

Antibiotic resistance - bacteria

Sickle-cell disease - malaria resistance

Etc

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4
Q

Gene flow (effects of evolution)

A

All the alleles in a population are known as the gene pool

Gene flow is movement of genes between populations
(Eg genetic exchange due to migration of fertile individuals or gamete’s between populations like pollen)

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5
Q

Effects of evolution: genetic drift

A

Chance alterations in a populations alleles frequencies

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6
Q

Effects of evolution: genetic drift (bottleneck)

A

Random chance

Size of a population is severely reduced

Reduces variation

Eg Northern Elephant Seal (Mirounga angustirostris) hunted by humans in 19th century, reduced to 20-30 individuals, due to hunting ban now 100,000 but genetic diversity is severely reduced

Eg King Penguin (Aptenodytes patagonicus) on Macquarie Island; decimated by blubber oil industry, island became reserved so the species able to bring back genetic diversity

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7
Q

Effects of evolution: genetic drift
(Founder effects)

A

One/few individuals of a species become founders of a new isolated population

Rare alleles in old population, may become significant in new population
- may be deterimental
- reduced genetic variation
- non-random distribution of genes

Eg Finches on Galapagos Islands
Eg Huntingtons disease alleles in Dutch Afrikaans settlers

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8
Q

Effects of evolution: natural selection

A

Differential success in reproduction, driven by (for example):
- climate
- avoidance of predators
- resistance to pesticides

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9
Q

Effects of evolution: modes of natural selection

A

All lead to non-random changes in allele frequency

Stabilising (Selects for most common characteristic)
Directional (Selects for one extreme characteristic)
Disruptive (Selects for 2 extreme characteristics)

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10
Q

Effects of evolution: Natural selection - stabilising

A

Both extremes are at a selective disadvantage

Eg cacti spine number,
Eg Bicyclus anynana , winged eyespots

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11
Q

Effects of evolution: Natural selection - directional

A

One extreme is at a selective disadvantage

Eg Sockeye salmon
Eg African cichlids

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12
Q

Effects of evolution: Natural selection - disruptive /diversifying

A

‘Average’ individuals are at selective disadvantage

Eg Rabbits
Eg Peppered moths

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13
Q

Population growth in evolution

A

Initial rapid growth of a low density population

Growth rate slows - maximum population size eventually reached (due to resources)

Carrying capacity - high density population

Different selection pressures act in each case

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14
Q

Population growth - high density populations

A

At high density populations, traits (adaptations) are favoured that enable reproduction with fewer resources

K-selection = density dependent

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15
Q

Population growth: Low density population

A

Selection favours traits that promote rapid reproduction

r-selection = density indepedent

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16
Q

What is speciation

A

Origin of a new species driven by population divergence.

2 types: allopatric speciation, sympatric speciation

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17
Q

Define population

A

(Population = group of individuals if same species living in a particular geographical location)

18
Q

Allopatric speciation

A

Populations forms a new species whilst geographically separated from its parent population

More likely in smaller, isolated populations

Some alleles may be lost

(physical separation - populations diverge - reproductive isolation/separation so unable to interbreed)

19
Q

Sympatric speciation

A

Occurs in geographically overlapping populations

Gene flow is reduced by chromosomal changes and non-random mating

(Mutation occurs, isolates sub population from parent (may be due to hybridisation, sexual/disruptive selection, habitat differentiation, etc) - appearance of reproductive barriers)

20
Q

Allopatric speciation: ring species

A

Populations distributed around a geographical barrier

Change in allele frequency across a cline

(Gradual changes within the ring species, but when either end of the species meet they cannot interbreed while those closer related can! Geographical selection in the same area has occurred)

21
Q

Sympatric speciation: hybridisation

A

Hybrid genomes are highly dynamic

May exploit Nobel ecological niches, relative to parents

Rapid evolutionary change

Incompatible combination of genes?

22
Q

Sympatric speciation: autopolyploidy

A

The chromosome divide, but the nucleus doesn’t

Chromosome number increases from a diploid to a tetraploid (4 copies per cell)

Effectively creates new species

23
Q

Sympatric speciation: habitat differentiation

A

New species evolve from a single ancestral species while inhabiting the same geographical region

Eg hummingbirds

24
Q

Reproductive barriers

A

Ensure new species keep separate identities

Can be:
Prezygotic
Postzygotic

25
Q

Reproductive barriers: Prezygotic

A

Impedes mating between species or fertilisation of ova if mating is attempted

Include:

habitat isolation (no overlap in space)

behavioural isolation (bird song for example)

Temporal isolation (eg 3 species living in same rainforest do not hybridise because they flower on different days)

Mechanical isolation (eg Bradybaena sp - shells spiral opposite direction, genital openings don’t align)

Gametic isolation (eg Strongylocebtrotus purpuratus)

26
Q

Reproductive barriers: postzygotic

A

Prevents any ovum fertilised by another species from developing into a viable fertile adult

Includes:
Reduced hybrid viability (eg Ensatina hybrid - Salamander)

Reduced hybrid fertility (eg Mules cannot backbreed, failure to produce functional gametes)

Hybrid breakdown (offspring of hybrids are feeble or sterile)

27
Q

Rates of evolution: Gradualism

A

Gradual evolutionary change - slow but constant rate of change

28
Q

Rates of evolution: Punctured equilibrium

A

Appearance of new characteristics give rise to new species relatively rapidly and then persist unchanged for a long time (equilibrium)

New innovations result in a new spurt of evolution which would result in a ‘punctuation’ of the fossil record

29
Q

Rates of evolution: gradualism or punctuated equilibrium?

A

Both seen in fossil record - some species change gradually over time and others appear abruptly, remain unchanged for millions of years and then go extinct

Fossil record interpretation issues: what is a species? At what point do we redefine species?

Estimates of speciation rates = 4000years (eg some fish) but up to 40 million years (eg some beetles)

Which is correct? Both?

30
Q

What is co-evolution

A

Occurs when selection pressures on one species are influenced by evolution of another species

Types:
- Inter-specific competition (resources between species)
- Exploitation (eg predation, host-parasite interaction)
- Mutualism

31
Q

What is character displacement

A

When similarity between species diverges when they share the same space and access to resources

Sympatry = Occur together, in the same space
Allopatry = Occur in separate space

32
Q

co-evolution: Exploitation example

Refer to Lecture 8 LEC 141 for more info

A

Cuckoos (brood parasite), they lay their eggs in the nest of other species. Other birds grow the cuckoos’ babies as if there own.

There will be strong selection on host to reject cuckoo eggs (as it impacts their reproductive success - some birds are discriminatory) also strong selection on cuckoo to ‘fool’ the host (often using mimicry and other adaptations to prevent their egg being rejected)

33
Q

Indirect co-evolution example

More info on L8 notes, LEC 141

A

Insect aposematism: warning colourisation and often poisoness

Gittleman & Harvey (1980) conducted chick experiments to understand how predators learn to avoid certain prey

34
Q

Co-evolution: Mutualism

A

Co-evolution through positive association

Eg pollination using flowers - adapted to attract insect pollinators, flowers advertise nectar for the bees, and in turn the bees pollinate the flower.
However some plants do lie and trick pollinator insects

35
Q

Co-evolution: The red queen hypothesis

A

An evolutionary hypothesis which proposes that species must constantly adapt, evolve and proliferate in order to survive while pitted against ever-evolving opposing species

36
Q

What are the two costs of reproduction

A
  1. Mating effort (works in both directions - male and female)
  2. Parental effort

This varies species to species

37
Q

What does mating effort include

A

Territory defence
Mate attraction
Female defence
Flower production
Nuptial gifts
Mate guarding effort

(For example peacock feathers evolved from sexual selection - however they become more obvious to predators so it comes with a cost)

38
Q

Parental effort includes

A

Investment in gamete’s
Parental care

Balance of this varies between species

The more young they have the more effort of care needed - additionally some male / female infants take more energy to care for than the other gender

(Many animals and plants don’t provide parental care)

39
Q

True or false

Within animals there tends to be few large offspring or many small ones

A

Trur

40
Q

Prenatal care differs between species

What are the costs of parental care

A

Environmental effects

Individual differences

Direct costs - energy and resources

Lost future reproductive opportunities

41
Q

What is parental investment

A

Resources allocated from parent to offspring which increase offspring viability at a cost to the parent

42
Q

What influenced ability of reproduction and parental care

A

Individuals within the population differ in resources available to them

Eg: territory quality varies, individuals are different ages, sizes, weights, etc

LEC 141 - Evolutionary Biology (4 decks)

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