Australian vertebrate evolution Flashcards
(74 cards)
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
2
Q
list 3 forms of evidence: existence of Gondwana
A
- matching geology
- matching fauna
- plate tectonic models
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
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
5
Q
plate tectonic models: features
A
- run back and forth
6
Q
Australian tectonic plate movement:
A
- one of fastest moving
- 7cm northward/ yr w slight rotation
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)
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)
9
Q
changing climate of Aus: 15 mya
A
15 mya: emergence of circumpolar current - climate increasingly arid
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
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
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
13
Q
Wallace Line:
A
faunal boundary line separating zoogeographical regions of asia and australiasia
14
Q
fossils:
A
poorly known as lil fossil evidence prior Oligocene (33.9mya)
- nice evidence of mammals in particular after that
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
16
Q
vicariance vs dispersal:
A
- galaxiids
- smelt
- cod
- their fam may have Gondwanan origins, debated
- marine phases to life history
17
Q
modern freshwater fish:
A
- relatively low diversity
- few are 1º freshwater
- majority marine derived
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
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
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
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
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)
23
Q
Aus climate today: list (8)
A
- extreme temp
- lil water
- high unpredictability
- erosion
- fire regimes
- poor soils
- low topography
- low 1º productivity
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
25
Aus climate today: 1º productivity
- poor soil
- low relief, geologically extremely stable (no volcanism)
- 1º productivity v low
26
Aus fauna today:
- 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
27
endemism:
- isolation led to high % of endemic species through adaptive radiation
- 92% plants
- 83% mammals
- 45% birds
- 89% reptiles
- >70% freshwater fish
28
responses to aridity: key features
- low average rainfall
- high evaporation
- unpredictability
- temp extremes
29
responses to aridity: how
- 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)
30
food/ energy: features
- 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
water: list 3 sources
- free standing
- food
- metabolic
32
water: free water
- unreliable
| - most spp will use if available
33
water: food
- most reliable, content varies w diet
34
water: metabolic supply
- not huge supply, tip scales in extreme conditions
35
water: vert features
- 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
water: management features
- preventing water loss (evaporation) vital, also thermoreg. (panting, licking, sweating)
- water loss can occur through skin, breathing surfaces, faeces, urine
37
water: management adaptations
- diet selection
- behaviour
- kidneys produce conc. urine
- dry faeces
- salt glands
38
temperature: features (ecto/endotherm)
- 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
temperature: adaptations
- 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
freshwater fish: adaptive strategies (and eg.)
- 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
amphibian: adaptations
- 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
reptile adaptive strategies: list 3
- ectothermic
- control over water
- cleidoic egg
43
reptile adaptive strategies: ectothermic
- low metabolism (and low energy requirements)
- not constrained by body form
- smaller body size
- different niche from birds/ mammals
44
reptile adaptive strategies: control over water
- 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
reptile adaptive strategies: cleidoic egg
- free from having aquatic larval stage
46
eg. thorny devil
- 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
birds: general features
- 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
birds: flight
- 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
birds: flight type- albatross
- gliding/ soaring
- high aspect ratio
- pointed wing tips
50
birds: flight type- crow
- agile flight
51
birds: flight type- eagle
gliding
- low aspect ratio
- slotted wings
52
birds: flight type- falcon
- high speed flight
| - pointed long wings
53
seed eaters: features
- 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
insectivores and raptors: water
- 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
insectivores and raptors: excretions
- 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
bird tricks:
- 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
eg. emu
- 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
birds: plant material
- 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
eg. southern cassowary
- 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
eg. lil penguin
- 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
mammal adaptation + diversification: general features
- 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
mammal adaptation + diversification: convergent evol
- koala= sloth
- kangaroos= antelopes
- marsupial equiv dogs, cats, moles,rodents etc.
- matched placental mammals
- adaptive radiations in parallel and independently
63
mammal adaptation + diversification: mammals
- live in burrows
- hibernate/ torpor
- nocturnal
- use water from food
- alter fur
- migrate
- unusual locomotion (fly/ hop)
- large body size (digestion)
64
mammal adaptation + diversification: mammal function
- high metabolic rates, high body temp (some flexibility) but also some constraints
65
mammal adaptation + diversification: small mammals
- <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
mammal adaptation + diversification: med mammals
- 300-8kg
- bilbies, rodents
- quoll
- golden bandicoot
- numbat
67
mammal adaptation + diversification: herbivores
- 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
mammal adaptation + diversification: large mammals
- >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
mammal adaptation + diversification: large mammals eg. wombats
- avoidance 1º tactic
- sleep in burrows, come out night
- mixed herbivorous
70
mammal adaptation + diversification: large mammals eg. koala
- gum leaves
- v low metabolic rate
- spend all day sleeping, digesting highly fibrous diet
71
eg. kangaroos:
- 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
where are placental mammals: Theory 1- missed the boat
- did not reach connect Aus before continents separated
73
where are placental mammals: Theory 2- couldn't hack it
- placentals present in early days but went extinct
| - couldn't adapt to dry, unpredictable conditions
74
where are placental mammals: marsupials pre-adaptation
- 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
