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Biology of Australian Flora and Fauna > Lecture 12- Animal adaptations to extreme environments: Arid Zone > Flashcards

Lecture 12- Animal adaptations to extreme environments: Arid Zone Flashcards

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1
Q

How dry is Australia?

A

2nd driest continent on earth (after Antarctica)

-70% of continent arid or semi-arid

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2
Q

What are the two predominant features that impact animals?

A
  1. Climate

2. Physiography (shape of land)

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3
Q

What are the current climatic zones in Australia?

A
  1. Tropical
  2. Arid
  3. Temperate
  4. Intermediate
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4
Q

What is rainfall like in Australia?

A
  • arid: defined as insufficient for agriculture
  • southern areas: below 250mm
  • northern areas: below 500 mm
  • seasonality: wet and dry seasons, but timing differs in north and south
  • patchy: within districts and between years
  • rainfall variation in arid Australia : 10% higher compared to other arid zones around the wolrd (e.g. Alice Springs: mean annual rainfall: 281mm, range: 60-903mm)
  • result: rainfall unpredictable and thus availability of food also unpredictable
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5
Q

What provides food for animals after rain?

A

-plant growth, flowering and seeds provide food for animals

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6
Q

What is the temperature like in the Australian arid zone?

A
  • temperature extremes
  • up to 45 degrees during the day
  • can reach freezing point during the night
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7
Q

What is the physiography of Australia?

A

a) Limited areas of ranges- only in Pilbara and central ranges (near Alice Springs), all below 1500m (ie. very low ranges)
b) vast flat areas (stony or sand), vast sand dunes and some low stony hills
c) landscape highly weathered= low nutrients: N and P

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8
Q

What do cracking soils provide for animals?

A
  • refuge for animals
  • e.g. Planigale: tiny marsupial, under 10g, about half of a mouse
  • don’t need much food, so can survive in the arid zoen where not much food
  • nocturnal behaviour is good as have areal predators
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9
Q

What are some examples of environments of arid zones?

A
  • stony desert or “gibber plain”
  • low stony dry hills in central Australia
  • low ranges e.g. Pilbara (especially in WA)
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10
Q

Does Australia have many sandy deserts?

A

-yes
-7 big ones
(Gibson, Greate Victoria, Little desert, great sandy, sturt tamany, simpson)
-mainly in the west central area

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11
Q

Does Australia have dunes?

A

have dunes in some places

  • no plant life
  • extremely inhospitable
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12
Q

What is common in the arid areas?

A
  • vast, very flat areas in the arid zone
  • in some, large areas of grasses (triodia)
  • spinifex is also a dominant grass in the arid zone (prickly and provides good hiding for animals)
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13
Q

What does the physiography and climate of Australian arid zone lead to?

A
  • leads to low productivity (ie. low plant growth) and therefore:
  • low food availability for animals
  • unpredictable food availability for animals
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14
Q

What are the problems for animals in the arid zone?

A
  • poor soils
  • overall low food availability and often low food quality
  • unpredictable water and food supplies
  • high temperatures (Jan/Feb above 40C)
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15
Q

What are the main survival strategies for animals in the arid zone?

A
  1. Drought evasive: not active dry periods i.e. dormant stage as egg or adult, develop and reproduce rapidly after heavy rains, OR leave drought areas
  2. Drought tolerant: often long-lived species- tolerate very low levels of moisture and food, behavioural strategies assist survival
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16
Q

What is the drought evasive strategy 1: dormant as egg or adult during dry times? Shield shrimps

A

e. g. Shield shrimp: when puddles dry out eggs can remain in suspended animation (diapause) for years
- eggs hatch and develop into adults very rapidly after rain
- incredibly fast life cycle (includes parthenogenic stages)

17
Q

What is the drought evasive strategy 1: dormant as egg or adult during dry times? burrowing frogs

A
  • water conservation strategies:
  • aestivation (lower their metabolism)
  • cocoon (store water)
  • reproductive strategies emerge and breed after rain
18
Q

What is the drought evasive strategy 1: dormant as egg or adult during dry times? burrowing frogs: Neobatrachus (trilling frog)

A
  • Neobatrachus centralis
  • 11 year study in arid South Australia
  • 150-200 forgs/ha
  • emerge after more than 5mm of rain (only occurred on 313 days in 11 years), females gravid, active ca 2 days
  • egg laying only 5 times in 11 years: always in summer and only when rain above 70 mm
  • successful recruitment of only 3 cohorts in 11 years
  • very rapid metamorphosis (17 days) in shallow pools but can be delayed up to 9 months if ponds are deeper
19
Q

What is the drought evasive strategy 2: migration in birds?

A
  • e.g. budgerigars (arid zone distribution)
  • behaviour: migratory/nomadic-flocks travels up to 1500km to find food and water
  • breed opportunistically when grass seeds become available after rain
20
Q

What is the drought-tolerant strategy in animals that insulate against extreme environment?

A
  • “Magnetic” termites
  • Mounds design reduces fluctuations in temperature N-S orientation
  • 95% humidity within mound
21
Q

What is the drought tolerant strategy: animals that remain active during dry times? (ants)

A
  • Honey pot ants
  • live in highly unpredictable environment
  • store food when it is abundant
  • workers serve as storage pots to feed colony
22
Q

What is the drought tolerant strategy in animals that remain active during dry times?

A

Arid zone mammals:

  • endotherms, thus need to balance thermoregulation with water gain and loss
  • avoid high temperature (behaviour: nocturnal, burrow)
  • regulate temperature (coat colour= white, evaporative cooling = tongue)
  • water conservation
23
Q

How does the southern hairy nosed wombat fare in the arid zone?

A
  • avoid high temperatures
  • spend very little time above ground (use burrows)
  • nocturnal
  • relatively low metabolic rate (for a mammal)
  • survive on low quality food
    (ie. pursues an energy conservation strategy)
24
Q

What is one endotherm strategy for dealing with high temperatures in the arid zone?

A
  • evaporative cooling
  • when air temperature exceeds body temperature,evaporative cooling is only option
  • sweating: generally too costly (mouse would loose more than 20% of body mass per hour)
  • panting: primary mechanism for mammals which are above 100g
  • salive spreading: wiped onto fore and hind limbs, subsequent evaporation cools the animal
25
Q

How do rock wallabies cool themselves?

A

-by licking their wrists (air flow cools blood in superficial veins)

26
Q

What are the water requirements like for animals?

A
  • lower for ectotherms probably no reptiles or invertebrates need to drink
  • endotherms have higher water requirements but only 4% mammals, 10% birds in arid zone need to drink (ie arid specialists)
  • animals obtain water from foods: insects are 70% H20, seeds low in water, water content of other plant tissue more variable
  • arid zone animals save water using specialised water conservation strategies
27
Q

How does the thorny devil fare in the arid zone?

A
  • maximising access to water
  • specialised skin texture (morphology) to capture dew and rainwater
  • scales are surrounded by tiny interconnected channels that attract water
  • water is then funnelled from these to the mouth
28
Q

What is the white-winged fairy wren?

A
  • a tiny arid zone specialist
  • lives in most of australia’s arid zone
  • food selection: diet of insects= high water content
29
Q

How does the Eyrean grasswren fare in the arid zone?

A

Physiology

  • have very efficient kidneys=water retention
  • don’t drink water at all
  • extract water from dry seeds and small insects
  • long thought to be extinct: secretive behaviour, remote distribution and low habitat disturbance (no cattle)
30
Q

What is the adaptation f small arid zone animals 1. Fat tailed dunnart?

A
  • energy conservation strategy
  • diet: insects (70% water)
  • low metabolic rate
  • torpor
  • fat storage in tail
31
Q

What is the adaptation f small arid zone animals 2. Snipifex hopping mouse?

A
  • water conservation strategy
  • diet: seeds (low in water)
  • respiratory water loss
  • dry faeces
  • super-concentrated urine
32
Q

How does the Euro kangaroo adapt to the arid zone?

A
  • Drought tolerant
  • food: browser, low water, high fibre content; present all year
  • physiology: efficient water conservation, low N requirements
  • movements: no, resident
33
Q

How does the Red kangaroo adapt to the arid zone?

A
  • drought evasive
  • food: grazer, higher water, lower fibre content, growth flush after rain
  • physiology: less efficient water conservation, N requirement not as low
  • movements: migrate

Biology of Australian Flora and Fauna (36 decks)

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