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VERTEBRATE EVOL > Australian vertebrate evolution > Flashcards

Australian vertebrate evolution Flashcards

1
Q

split of supercontinent: features

A
  • all landforms joined together 550-180 million yrs ago (Pangaea)
  • 180 million yrs ago (Jurassic) split into supercontinent: Gondwana + Laurasia
  • Gondwana= Australia, Africa, Madagascar, NZ, S America, India
  • 45 million yrs ago, Aus split from Antarctica
  • Aus isolated as it moved north towards equator
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2
Q

list 3 forms of evidence: existence of Gondwana

A
  • matching geology
  • matching fauna
  • plate tectonic models
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3
Q

matching geology features:

A
  • rock strata around continental margins match exactly in many places
  • SA and Antarctica
  • W Africa and E South America
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4
Q

matching fauna: features

A
  • many groups of animals in Aus have close relos in S America, Africa, India, NZ,
  • NOT northern asia, europe, N america
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5
Q

plate tectonic models: features

A
  • run back and forth
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6
Q

Australian tectonic plate movement:

A
  • one of fastest moving

- 7cm northward/ yr w slight rotation

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7
Q

changing climate of Aus: 100 mya

A

100 mya: Aus + Antarctica joined, climate cool and wet - covered in temperate rainforest (Antarctica ice free)

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8
Q

changing climate of Aus: 45 mya

A

45 mya: split Aus became drier and warmer, less rainforests more schlerophyll + grasslands
- Aus moved north of Tropic of Capricorn (northern edge was tropical)

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9
Q

changing climate of Aus: 15 mya

A

15 mya: emergence of circumpolar current - climate increasingly arid

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10
Q

isolation:

A
  • long history of isolation, before split was peninsula of Gondwana
  • already low diversity before being island
  • may explain lack of placental mammals, oddities
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11
Q

peninsular effect:

A
  • faunas progressively impoverished from mainland to out edge of peninsula
  • therefore unique fauna og from Gondwana survived and adapted to Aus’ changing env
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12
Q

Aus contact:

A
  • Aus plate crashed into Asia allowing limited faunal exchange
  • glacial period sea lvls low, nearly united continental shelves
  • deep water trenches separated flora and fauna of Aus to asia
  • 15mya gained some bats, birds, small reptiles
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13
Q

Wallace Line:

A

faunal boundary line separating zoogeographical regions of asia and australiasia

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14
Q

fossils:

A

poorly known as lil fossil evidence prior Oligocene (33.9mya)
- nice evidence of mammals in particular after that

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15
Q

Aus freshwater fish: origins

A
  • prior to Oligocene evidence scarce
  • lungfish in Koonwarra Lake: Aus part of Gondwana (cool alpine env)
  • bony tongue fish also date back to Gondwana
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16
Q

vicariance vs dispersal:

A
  • galaxiids
  • smelt
  • cod
  • their fam may have Gondwanan origins, debated
  • marine phases to life history
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17
Q

modern freshwater fish:

A
  • relatively low diversity
  • few are 1º freshwater
  • majority marine derived
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18
Q

monotremes:

A
  • lay eggs
  • cloaca (monotreme= single opening)
  • no nipples
  • our fauna dominated by them
  • echidna diverged from platypus but retained electrosensitivity (not useful on land)
  • ancestors found in Antarctica and S America
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19
Q

reptiles and amphibians of ancient Aus:

A
  • amphibians and reptiles all present in fossil record
  • however no evidence of aridity, but warm, moist forested
  • Miocene (6mya) shift of increasing aridity and shift in fauna
  • no land based tortoises, venomous snakes outnumber non-v
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20
Q

marsupial origins:

A
  • first ancestor 125mya in NE china (Siberia)
  • oldest fossils in Aus 55mya
  • Coloco opossum only living member sharing common ancestor w modern Aus marsupials
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21
Q

Miocene-Pliocene boundary: survivors

A
  • some genera persisted from Miocene to present many had specialised niches, marsupial moles, m. carnivore (Thylacine)
  • connection to asia was firmly established, during low sea lvls Aus and NG continuously connected via land bridge
  • refuge for cassowary, possums, tree kangaroos and wallabies
  • big changes in diversity, diet, geographic distributions
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22
Q

Pleistocene rollercoaster/ extinctions:

A
  • 360k ya extreme shift in dist and abundance of taxa
  • 4 glacia maxima= extreme aridity exemplified by dune fields, leoss deposits
  • much of taxa confined to refugia –> promoted allopatric speciation
  • Pleistocene megafauna extinction in particular (many widespread extinctions)
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23
Q

Aus climate today: list (8)

A
  • extreme temp
  • lil water
  • high unpredictability
  • erosion
  • fire regimes
  • poor soils
  • low topography
  • low 1º productivity
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24
Q

Aus climate today: features

A
  • Aus big land size= many diff climate zones:
  • north: tropical influences (hot humid summer, warm dry winter)
  • south: cooler, mild summer, cool rainy winter
  • driest inhabited continent
  • lowest runoff, water in rivers, smallest area of permanent wetlands of continents
  • most variable rainfall
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25
Q

Aus climate today: 1º productivity

A
  • poor soil
  • low relief, geologically extremely stable (no volcanism)
  • 1º productivity v low
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26
Q

Aus fauna today:

A
  • combo of isolation and severe selection of species who could adapt to arid, unpredictable env/ find refuge
  • survive repeated climate catastrophes
  • not v diverse
  • highly unique
  • living fossils (lungfish, monotremes, tuatara only surviving relo of snakes/ lizards)
  • mammal fauna dom by marsupials not placentals
  • huge no. parrots
  • crazy diversity reptiles
  • snake fauna dom venomous elapids vs. colubrids
  • frogs dom by myobatrachids
  • freshwater fish nearly all marine derived
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27
Q

endemism:

A
  • isolation led to high % of endemic species through adaptive radiation
  • 92% plants
  • 83% mammals
  • 45% birds
  • 89% reptiles
  • > 70% freshwater fish
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28
Q

responses to aridity: key features

A
  • low average rainfall
  • high evaporation
  • unpredictability
  • temp extremes
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29
Q

responses to aridity: how

A
  • rainfall controls 1º production
  • all Aus verts (incl fish) have to adapt to conditions/ access to refugia
  • to persist, need access to predictable and adequate supply food, cope w temp extremes
  • access to water and temp extremes provide immediate stresses, but w constant background of low energy env (main constraint)
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30
Q

food/ energy: features

A
  • plants basis of energy production, highly dependent on rainfall
  • eg. Fowler’s gap (NSW) 9-77% ground cover el Nino/ la Nina cycles
  • not enough animals to utilise good growth, invert break down old materials - vert eat inverts and seeds
  • seedbanks and insect pop far more dependable sources of energy
31
Q

water: list 3 sources

A
  • free standing
  • food
  • metabolic
32
Q

water: free water

A
  • unreliable

- most spp will use if available

33
Q

water: food

A
  • most reliable, content varies w diet
34
Q

water: metabolic supply

A
  • not huge supply, tip scales in extreme conditions
35
Q

water: vert features

A
  • all vert must maintain optimal osmotic balance for survival
  • some species (eg. desert frogs) evolved cope well out of optima, limits to what they can stand
36
Q

water: management features

A
  • preventing water loss (evaporation) vital, also thermoreg. (panting, licking, sweating)
  • water loss can occur through skin, breathing surfaces, faeces, urine
37
Q

water: management adaptations

A
  • diet selection
  • behaviour
  • kidneys produce conc. urine
  • dry faeces
  • salt glands
38
Q

temperature: features (ecto/endotherm)

A
  • deserts can go v hot to cold
  • lack moisture = no cloud cover

ectotherm: shuttle from sun - shade to control temp
endotherm: seek shelter from extremes

39
Q

temperature: adaptations

A
  • living in burrows (reduces temp variability, increase humidity)
  • some birds/mammals cope w high temp via evaporative cooling (water dependent)
  • animals highly mobile (nomadic) to avoid extremes, or only active at night
40
Q

freshwater fish: adaptive strategies (and eg.)

A
  • massive river sys through arid zones (desert) but go through boom bust cycles depending on rainfall/ flood events
  • life cycle of Aus fish ties to events
  • respond to flood by migrating upstream to spawn, larvae dev in rich conditions
  • during droughts, fish retreat to deep pool refugia
  • some fish aestivate: salamander and some galaxiid lie dormant under logs, stones, burrows waiting for rain to return
  • eg. desert goby: tolerate extremes in temp and salinity
41
Q

amphibian: adaptations

A
  • 5 families of frogs in Aus (eg. cane toad)
  • 2 are Gondwanan og, developed behavioural, anatomical and physiological mechanisms coping w dry, unpredictable env
  • as frogs loose water through skin, highly susceptible to dry conditions
  • some reduce water across skin, some large bladders store dilute urine, borrow, aestivate w/without cocoon
  • reproduction: direct dev used as usually tadpoles rely on water
42
Q

reptile adaptive strategies: list 3

A
  • ectothermic
  • control over water
  • cleidoic egg
43
Q

reptile adaptive strategies: ectothermic

A
  • low metabolism (and low energy requirements)
  • not constrained by body form
  • smaller body size
  • different niche from birds/ mammals
44
Q

reptile adaptive strategies: control over water

A
  • stratum corneum (dead skin layer barrier to diffusion)
  • uric acid as principal waste - precipitate as salt, saving water loss (eg. shingleback have salt glands excreting salt directly)
45
Q

reptile adaptive strategies: cleidoic egg

A
  • free from having aquatic larval stage
46
Q

eg. thorny devil

A
  • specialist ant eater, all food and water needs from diet
  • absorbs water via capillary action (when rain, wet soil)
  • skin impermeable but capillaries run to mouth
  • camoflaged
  • fake head
  • sharp spines
  • squared legs for rapid movement
47
Q

birds: general features

A
  • retained some adaptations from reptilian ancestors, improved water conservation mechanisms
  • endothermic
  • flight= dispersal abilities at relatively low cost
  • forage for water/food over wide distances
  • during hot summer need daily access to free water
48
Q

birds: flight

A
  • constrained by body size: bigger= more energy
  • many arid zone birds small/ spend alot of time on ground (bustards)
  • larger raptors (eg. eagles) soar in upwelling winds reduce energy expenditure
49
Q

birds: flight type- albatross

A
  • gliding/ soaring
  • high aspect ratio
  • pointed wing tips
50
Q

birds: flight type- crow

A
  • agile flight
51
Q

birds: flight type- eagle

A

gliding

  • low aspect ratio
  • slotted wings
52
Q

birds: flight type- falcon

A
  • high speed flight

- pointed long wings

53
Q

seed eaters: features

A
  • many arid zone birds rely on seeds (44% individuals, 17% species)
  • abundant but low on water
  • most birds diurnal, must forage at day when v hot
  • zebra finches, budgies get by cool months without drinking, but once warm must have access to water
  • huge flocks of birds visit water holes in evenings
54
Q

insectivores and raptors: water

A
  • vital food source: insect and larvae for arid zone birds
  • raptors important as eat reptiles
  • both relatively high water content, birds may not need to drink at all
55
Q

insectivores and raptors: excretions

A
  • nitrogenous waste as semi solid uric acid/ urate
  • kidneys produce moderately conc. urine (not as conc. as mammals tho)
  • water birds also have salt glands
56
Q

bird tricks:

A
  • high body temp: export heat to air at greater temp (spinifex pigeons tolerate temps ~45º)
  • unique respiratory sys enables resp. cooling w limited loss of water
  • incredibly tolerant of dehydration
  • eg. zebra finches loose 30% body mass in water loss, (would kill humans)
  • nomadic
57
Q

eg. emu

A
  • facultative fermenters (unusually small gut)
  • mixed diet: herbivores so less reliant on fermentation
  • during bad times: alter gut processes to digest more fibre
  • travel long distances to acquire food
  • light bones, fast metabolism enable to run v efficiently
  • feathers reflect sunlight (deflect solar radiation) and keep warm in winter
58
Q

birds: plant material

A
  • digestive requirements restricted by weight
  • must eat alot of plants, too big to fly
  • ratites (ostriches) hind-gut fermenters rely on microbial action to breakdown food
59
Q

eg. southern cassowary

A
  • tough bristle-like feathers
  • ratite lives in dense rainforest (tip of QLD and NG) can camo
  • diet of fallen fruit and fungi
  • closely related to kiwi birds
  • horny casque on head (heat loss mechanism)
  • long range hearing
  • elongated sharp inner claw (defence, easily kill humans/ dogs when threatened)
  • digestion copes w toxins
60
Q

eg. lil penguin

A
  • 10 000 feathers for insulation
  • wings act as fins to propel through water
  • dense feathers act as insulation, counter-shaded (camo)
  • dense bones: diving
  • gland produce oil substance on feathers- waterproofing
  • salt gland- excrete excess salt
  • streamlined shape
  • eat anchovy, sprate, sardines, krill, squid as dive under water for short periods of time
  • return to shore to nest in burrows in nesting colonies and moult
  • 80% life spent at sea
61
Q

mammal adaptation + diversification: general features

A
  • Aus isolated and increasingly arid, marsupial fauna underwent adaptive radiation
  • adapted to niches in latter part of Miocene, insectivore/ carnivore marsupials experienced diversification surge
62
Q

mammal adaptation + diversification: convergent evol

A
  • koala= sloth
  • kangaroos= antelopes
  • marsupial equiv dogs, cats, moles,rodents etc.
  • matched placental mammals
  • adaptive radiations in parallel and independently
63
Q

mammal adaptation + diversification: mammals

A
  • live in burrows
  • hibernate/ torpor
  • nocturnal
  • use water from food
  • alter fur
  • migrate
  • unusual locomotion (fly/ hop)
  • large body size (digestion)
64
Q

mammal adaptation + diversification: mammal function

A
  • high metabolic rates, high body temp (some flexibility) but also some constraints
65
Q

mammal adaptation + diversification: small mammals

A
  • <300g
  • limited: most live in burrows
  • sml must eat easily digested food, insects, seeds, soft vegetation
  • dasyurids (mostly insectivores), rodents (granivores)
  • kidneys extremely effective produce conc. urine (eg. hopping mice)
  • enter torpor on daily basis to conserve energy/ low basal metabolisms
  • eg. mircrobats
66
Q

mammal adaptation + diversification: med mammals

A
  • 300-8kg
  • bilbies, rodents
  • quoll
  • golden bandicoot
  • numbat
67
Q

mammal adaptation + diversification: herbivores

A
  • excellent water conservation abilities, don’t need to drink
  • all use fermentation to digest (smaller rely less as bigger animals eat grasses, seeds more fibre)
68
Q

mammal adaptation + diversification: large mammals

A
  • > 8kg
  • dingo, koala, wombat, macropod, kangaroos, wallabies
  • water loss reduced, high thermal inertia
  • metabolic rate reduced
  • lrg digestive system (microbial fermentation processes)
  • travel further distances
69
Q

mammal adaptation + diversification: large mammals eg. wombats

A
  • avoidance 1º tactic
  • sleep in burrows, come out night
  • mixed herbivorous
70
Q

mammal adaptation + diversification: large mammals eg. koala

A
  • gum leaves
  • v low metabolic rate
  • spend all day sleeping, digesting highly fibrous diet
71
Q

eg. kangaroos:

A
  • highly mobile (hopping)
  • efficient digestion of fibre
  • behavioural: seek shade/sun as needed
  • nocturnal esp summer
  • produce highly conc. urine
  • sophisticated physiological thermal regulation
  • rarely need to drink in summer (
72
Q

where are placental mammals: Theory 1- missed the boat

A
  • did not reach connect Aus before continents separated
73
Q

where are placental mammals: Theory 2- couldn’t hack it

A
  • placentals present in early days but went extinct

- couldn’t adapt to dry, unpredictable conditions

74
Q

where are placental mammals: marsupials pre-adaptation

A
  • hopping covers long distances w less energy
  • reproductive flexibility: young at 3 stages of dev simultaneously
  • many live in burrows
  • many nocturnal
  • low metabolic rate

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