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Zoology Y1 > APS11006 Principles of Evolution- Thomas Lectures > Flashcards

APS11006 Principles of Evolution- Thomas Lectures Flashcards

1
Q

Microevolution

A

Changes within a species

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2
Q

Macroevolution

A

Patterns of evolutionary change above the species level

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3
Q

How does speciation occur?

A
  • Biological species and reproductive isolation

- Low gene flow and disruptive selection

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4
Q

Definition of biological species

A

“A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring- but do not produce viable, fertile offspring with members of other such groups”

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5
Q

Reproductive isolation

A
  • Existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring
  • Geographic, behavioural and temporal isolation (breeding times)
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6
Q

Which type of selection is expected to be associated with speciation?

A
  • Disruptive selection
  • Drives two or more peaks in fitness
  • Pushes means or groups of populations apart, causing divergence in phenotypes
  • When populations become so phenotypically different that they cannot interbreed, this is speciation
  • Disruptive selection can be countered by gene flow
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7
Q

Gene flow

A

Exchange of genes between populations as a result of movement and interbreeding of individuals

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8
Q

How does gene flow counter disruptive selection?

A
  • One island favours yellow, the other favours orange

- If individuals can move freely between islands and interbreed, mixed populations occur, not divergent populations

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9
Q

Allopatric speciation

A
  • Speciation with geographic isolation
  • Long term isolation can result in phenotypic divergence due to different selection pressures and random genetic drift
  • If populations cannot interbreed, speciation has occurred
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10
Q

Organism’s dispersal ability

A

The extent to which an organism can overcome a barrier

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11
Q

Sympatric speciation

A

Splitting of an ancestral species into two or more reproductively isolated groups with geographic isolation

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12
Q

Causes of reproductive isolation

A
  • Geographical isolation
  • Behavioural isolation
  • Temporal isolation
  • Disruptive selection
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13
Q

Sympatric meaning

A

Occurring within same or overlapping geographical location

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14
Q

Rhagoletic polmonella- North American apple maggot fly

A
  • Native plant is hawthorn, usually mates on or near
  • Apple trees introduce, sympatric to hawthorn
  • Habitat isolation is a pre-zygotic barrier
  • Apples mature faster, so timing of feeding and therefore mating is another pre-zygotic barrier
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15
Q

Rate of evolution- gradualism

A
  • Steady change over time, no jumps in characteristics
  • Expected outcome from microevolution
  • Accumulation of small stepwise changes over time, each generation producing a small change
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16
Q

Why are there gaps in the fossil record?

A
  • Fossil record represents between 1 and 5% of species that have existed
  • Fossilisation requires death (inevitable), burial with organism mostly intact (rare due to scavenging and decay), sedimentation (rare in terrestrial environments) and survival of sedimentary rocks (rare as geological processes repeatedly destroy sedimentary layers)
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17
Q

Rate of evolution- punctuated equilibrium

A
  • Proposed by Stephen J Gould and Niles Eldredge
  • Rates of evolutionary change during and between speciation events are different because different processes are at work
  • Not fully accepted due to vague mechanisms
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18
Q

Can selection explain stasis?

A
  • Horseshoe crabs and Nautilus have remained morphologically unchanged for tens of millions of years
  • How have they managed this given that selection happens all the time?
  • Stabilising selection
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19
Q

Patterns of evolution

A
  • Divergent

- Convergent

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20
Q

Convergent evolution

A
  • Lineages that are not closely related evolve similar adaptations because they live in similar environments
  • E.g., aardvarks, anteaters, pangolins (share diet), morphology has converged, forming long snouts good for digging into termite mounds
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21
Q

Anolis lizard

A
  • 200 mainland species, 150 Caribbean
  • Classed into six ‘ecomorphs’: crown-giant, twig, grass-bush, trunk-crown, trunk, trunk-ground
  • Morphologically and behaviourally distinct based on their microhabitat
22
Q

What causes adaptive radiation?

A

Ecological opportunity

23
Q

Example of adaptive radiation

A

Rapid diversification of mammals after mass extinction of dinosaurs

24
Q

Morphological expansion of the Acanthomorpha

A
  • Spiny finned teleost fish
  • Low morphological diversity before Cretaceous-Palaeogene boundary
  • After extinction of competitors, morphospace expanded into vacated niches
25
Q

Key innovation

A

Evolution of some particular trait that opens up opportunity to exploit different niches e.g. toe pads in Anolis facilitate exploitation of arboreal niches

26
Q

Types of extinction

A
  • Contemporary e.g. local and species

- Geological e.g. background, mass

27
Q

How many species are threatened with extinction?

A
  • 1 million

- Average of 25% of species in any taxonomic group

28
Q

Local extinction

A
  • Loss of population from a particular area

- E.g. wolves from Britain

29
Q

Barn owl trust

A

Protect species that are threatened in UK but safe on global scale

30
Q

Species extinction example

A
  • Passenger pigeons, used to be billions (flock of them crossed US prairies for 14 hours)
  • Were hunted to extinction very rapidly
  • Martha, the last surviving pigeon, died in Cincinnati Zoo in 1914
31
Q

What % of all species that have existed have gone extinct

A

99

32
Q

Extinction in fossil record

A
  • Background, sum of all normal species terminations during a defined time
  • Extinction events, times when many species go extinct for a shared reason, typically regional
  • Mass extinctions, times of geologically rapid global disappearance of much of life
33
Q

Why is it difficult to measure extinction rates using fossil record?

A
  • Incomplete
  • Classification of species from fossil record is challenge
  • Sometimes higher taxa are used
34
Q

Raup and Seposki, 1992

A
  • Wrote series of papers on marine fossil record
  • Explored patterns spanning 600million years
  • Measured s number of families gone extinct per year
  • Good estimate for background extinction rates
35
Q

End-Ordovician mass extinction

A
  • 444 mya
  • Declines in nautiloids, trilobites, brachiopods, crinoids, bryzoans, corals
  • None completely wiped out
  • Caused by glaciation
  • Around 700 genera lost
36
Q

Late Devonian mass extinction

A
  • 372 mya
  • Declines in trilobites, brachiopods, bivalves, corals, nautiloids, sponges, crinoids, and various fish
  • Complete loss of ostracoderms and placoderms
  • Caused by LIP shifts associated with volcanic activity, and ocean anoxia
37
Q

End-Permian mass extinction

A
  • 252 mya
  • Largest event of all
  • Declines in brachiopods, crinoids, synapsids
  • Loss of blastoids, trilobites, rugose and tabulate corals and pareiasaurs
  • Caused by LIP and ocean anoxia
38
Q

End-Triassic mass extinction

A
  • 201 mya
  • Declines in bivalves, ammonoids, gastropods
  • Loss of conodonts and basal archosaurs
  • Caused by LIP and ocean anoxia
39
Q

End-Cretaceous mass extinction

A
  • 66mya
  • Declines in bivalves, gastropods, foraminifera
  • Loss of dinosaurs, pterosaurs, plesiosaurs, mosasaurs, ammonites, belemites
  • Caused by meteor impact in Mexico and LIP
40
Q

Example of a species becoming cosmopolitan

A
  • Lystrosaurus after end-Permian mass extinction now had almost no predators and barely any herbivore competition
  • Was at one time one of the most successful vertebrates on Earth
41
Q

How can measuring past extinction events, including mass extinctions, help us
to understand the current biodiversity crisis?

A

Characteristics of survivors of mass extinctions may indicate trajectories of recovery if the current extinction crisis proceeds unchecked.

42
Q

Significance of mass extinctions for modern conservation concerns

A
  • If a mass extinction removes certain species from ecosystems, the scaffold ecosystem may be available after crisis for new species to occupy
  • But, if most components of ecosystem are removed by larger event, recovery may involve the construction of new ecosystems
  • Those that survive have big impact on future
43
Q

Species senescence

A
  • Now disproved theory
  • Suggests that species undergo lifecycles like individuals do
  • Birth, development, reproduction, death
  • Orthogenesis, change in organisms was not due to natural selection, but due to unchecked directional trends within a lineage
44
Q

‘Example’ of senescence

A
  • Irish Elk
  • Evolved on an irreversible trajectory towards larger and larger antlers
  • Irish Elk went extinct when antlers became too large
  • Could no longer hold up heads and got tangled in trees
  • Inevitably went towards larger and larger antlers?
45
Q

More likely explanation for extinction of Irish Elk

A
  • Sexual selection favoured large antlers and large body size
  • Natural selection favoured smaller size in response to rapid change towards warmer, more temperate climates at the end of the last ice age
46
Q

Competition and the Red Queen

A
  • Competition theory of extinction named after Red Queen from Through the Looking-Glass
  • “Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast”
47
Q

Environment and the Court Jester

A
  • Environmental theory of extinction
  • Random, unpredictable changes to physical environment such as climate change, tectonic events, or even bolide impacts (meteors)
48
Q

Planktonic foraminifera

A
  • Exceptionally well preserved fossil record
  • Microorganisms that live in oceans, shells are deposited in sediment after death
  • Change in morphology over time has been well documented
  • Clues to extinction drivers
49
Q

Broad sense species selection

A
  • Aggregate traits e.g, body size

- Can take an average of all the individuals across the species to compare to other organisms

50
Q

Strict sense species selection

A
  • Emergent traits e.g., range size
  • Traits that can only be measured across the whole species, no average can be taken as the geographic cover of a species is shared by all individuals of that species

Zoology Y1 (5 decks)

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