Temperature Regulation
 identify the broad range of temperatures over which life is found
compared with the narrow limits for individual species
 compare responses of named Australian ectothermic and endothermic
organisms to changes in the ambient temperature and explain how these
responses assist temperature regulation
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Temperature
 Temperature is one of the many limiting factors that
can determine the presence of life on Earth.
 Chemical reactions that take place in cells occur within
a relatively narrow range of temperatures due to the
temperature sensitivity of enzymes.
 Tissue temperatures above 42 °C causes important
enzymes to denature resulting in reduced ability to
function and affecting metabolism. Temperatures
above 100 °C causes proteins and DNA to denature,
resulting in cell death.
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Temperature and organisms
 Living creatures can survive in temperatures as low as
-70 °C at the poles or as high as 56 °C in deserts and
350 °C in hot vents in the sea.
 HOWEVER, individual species cannot survive in an
environment with a temperature range this large.
They need much narrower ranges.
 The temperature range in which a species can survive
is known as its tolerance range for temperature. This
is the degree to which an organism can tolerate and
survive a significant variation in environmental factors
including extremes such as drought, salinity and flood.
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Examples
The most heat tolerant organism known is the
Pompeii worm (Alvinella pompejana). It lives in
tubes on the sea floor near hydrothermal vents.
They have been found to be living in water with a
high temperature of 80°C and a low of 22°C
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Australian examples
The water-holding
frog (Cyclorama
platycephala) can
survive between
temperatures of
3°C and 39°C
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Australian examples
 Some Australian plants can survive the extreme heat
of fires.
 The banksia relies on the heat of the fire for seed
release. Bottlebrush trees have buds in a protected
position beneath the bark which resprout after fire.
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Ectotherms
 Have a limited ability to control their body
temperature
 Their cellular activities generate little heat
 Their body temperature rises and falls with ambient
temperature changes
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Examples of ectotherms
From the list below select the ectotherms
Plants
Amphibians
Mammals
Reptiles
Marsupials
Birds
Fish
Invertebrates
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Yay!
Nay!
Endotherms
 Their body metabolism generates heat
 Metabolic processes maintain an internal body
temperature that is independent of the external
temperature.
 To do this requires energy, so more food is required by
the endotherms.
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Examples of endotherms
From the list below select the endotherms
Plants
Amphibians
Mammals
Reptiles
Marsupials
Birds
Fish
Invertebrates
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Yay!
Nay!
Australian ectothermic organisms
Central netted dragon
Eastern brown snake
Bogong moths
Central netted dragon
The central netted dragon (Ctenophorus
nuchalis) is an Australian desert-adapted
lizard that inhabits central Australia’s
plains and open scrub. It is able to
withstand variations in body
temperature from 13 to 44°C.
The central netted dragon climbs up into trees or bushes when it
is very hot to seek cooler conditions off the ground. It will then
emerge at night to hunt when it is cool.
In low ambient temperatures, the dragon will lie in sunlight and
alter its body position to expose more of its body surface area to
the sun’s rays. This increases its core body temperature.
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Central netted dragon
The central netted dragon seeks shelter when it is too
hot and exposes its body to the sun to increase core
temperature. This is an example of a:
Behavioural adaptation
Structural adaptation
Physiological adaptation
Yay!
Nay!
Eastern brown snake
The eastern brown snake (Psudonaja textilis) is
found in the hot, dry areas of Australia, along the
eastern sea board.
The inhabit a wide variety of habitats including
open grasslands and desert scrub.
They are usual diurnal (awake during the day),
but can become more active at night if the
daytime temperature is too hot.
If the temperature is too low, they bask in
sunlight to gain additional heat.
In very cool weather, they become less active, slowing down their
metabolism and using fat reserves. If the cold period is prolonged, for
example in winter, the snake will hibernate in a sheltered spot.
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Eastern brown snake
Being active at night is referred to as being:
Diurnal
Hibernation
Nocturnal
Yay!
Nay!
Eastern brown snake
The eastern brown snake becomes more active at night
when the ambient temperature is too high for them.
This is an example of a:
Behavioural adaptation
Structural adaptation
Physiological adaptation
Yay!
Nay!
Bogong moths
Bogong moths (Agrotis infusa) migrate in huge
swarms to the Australian alps in summer to
aestivate cool caves.
Aestivation is a term that is used for animals
that ‘hibernate’ in hot conditions.
Arriving around November, Bogong Moths
cover the walls of alpine caves over
summer – up to 17 000 moths in one
square metre. They create a massive
influx of high-fat, high-protein food to
alpine ecosystems and are feasted upon
by marsupials.
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Australian endothermic organisms
Common bentwing bat
Fairy penguins
Mountain pygmy possum
Common bentwing bat
The common bentwing bat
(Miniopterus scheribersii) produces
brown fat in late summer and through
autumn when food is abundant.
Brown fat is a special heat producing
tissue that can be quickly metabolised
in cold conditions.
In the cold winter months, periods of
torpor can last up to 12 days.
Torpor is a period of temporary
hibernation.
The brown fat can be metabolised and is used to increase the body
temperature, allowing these bats to fly after periods of torpor.
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Fairy Penguins
The fairy penguin
(Eudyptula minor) is found
along the southern
Australian coastline and in
Tasmania and New
Zealand. It is the smallest
of all penguins and lives in
burrows in coastal sand
dunes.
Fairy penguins have feathers that provide an insulating layer, trapping a
layer of air close to the skin reduces the amount of heat lost.
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Fairy penguins
In cold weather the feathers of a fairy penguin
would lie:
Close to the skin
Away from the skin
They don’t change
Boo yah!
In cold conditions, the feathers of the fairy penguin are
lifted away from the skin, increasing the air layer and
providing a greater degree of insulation.
In hotter conditions, the fairy penguins’ feathers lie flat
against the skin, trapping a smaller amount of air.
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Not quite... Try again!
Fairy penguins
Fairy penguins can regulate their
body temperature via behavioural
mechanisms.
In warmer ambient conditions, they
can move into the water to cool
down.
In cool conditions, they can huddle
close together to reduce the surface
area of each penguin exposed to the
cold. They may also retreat to their
burrows.
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Mountain pygmy possum
The mountain pygmy possum
(Burramys parvus) lives above 1400
metres in the alpine regions of southeastern Australia.
It has short legs, a round body and
small ears with limited circulation
which assist in minimising heat loss.
In prolonged cold, during winter months, they hibernate and go into a state of
torpor. The pygmy possums curl into a ball, drawing all appendages in towards
the body to reduce the surface area exposed to the cold. They also use a
burrow to shelter from the cold in shorter periods of low ambient
temperature.
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Mountain pygmy possum
To avoid overheating, mountain pygmy
possums are nocturnal marsupials.
During the day they shelter in rock
crevices and this behaviour allows
them to avoid exposure to excessive
temperatures (and predators) and to
keep their metabolic rate low during
the heat of the day.
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Mountain pygmy possum
The mountain pygmy possum has short legs, a round body
and small ears. This is an example of:
Behavioural adaptation
Structural adaptation
Physiological adaptation
Yay!
Nay!
Adaptations
• analyse information from secondary sources
to describe adaptations and responses that
have occurred in Australian organisms to
assist temperature regulation
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Adaptations
Adaptations are characteristics that
increase the survival and reproductive
chances of an organism in its
environment.
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Adaptations
Adaptation is not:
A change that an organism makes in response
to the environment to help it survive
A variation that arises in individuals and have a
genetic basis
Woo!
Noo!
Adaptations
 Adaptation is usually a variation that arises
in individuals and has a genetic basis.
 Natural selection acts upon these variations
so that those that suit the organism to its
environment are passed on within a
population.
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Adaptations
Natural selection is also known as:
Flight or fight
Survival of the fittest
Convergent evolution
Woo!
Noo!
Adaptations
Adaptations are divided into three major categories.
Behavioural
Physiological
Structural
Behavioural adaptations
 Behavioural adaptations are adaptations to the way
the organism acts
 They are displayed by both ectotherms and
endotherms
Controlling exposure
Nocturnal activity
Migration
Controlling exposure
 Changing position of body in order to
increase or decrease amount of surface
area exposed to sunlight
 Organisms can do this by seeking
shade or shelter in burrows
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Water holding frog
Retires to a burrow in
extreme temperature
conditions. In very arid
conditions it lives in a
cocoon made of
secreted mucus and its
cast off skin, which is
shed after rain and then
dries out. This minimises
exposure to heat as well
as reducing water loss
and dehydration.
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Nocturnal activity
When the daytime temperature is very hot, animals
remain relatively inactive during the heat of the day.
This ensures that they do not generate additional
metabolic body heat as a result of increased activity.
This adaptation is seen in many reptiles and birds that
inhabit hot, arid areas as well as in the few mammals
that are able to survive desert conditions.
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Migration
Migration requires organisms to
physically move to a different
habitat that is within their
tolerance range.
The grey plover (Pluvialis
squatarola) breeds in the
Northern Hemisphere between
May and August and then
migrates to Australia over
August and stays until April. This
migration allows the birds to
avoid severe weather during
winter.
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Structural Adaptations
 Structural adaptations are changes in the physical
characteristics of the organism.
 Structural adaptations that assist with temperature
control are:
Insulation
Surface area to volume ratio
Colouration
Insulation
 Insulation such as fur, hair, feathers and coats enable a
layer of air to be trapped to reduce the amount of
heat lost.
 This layer of trapped air slows down the heat
exchange with the environment. The thickness can be
increased in cold conditions by contracting the
muscles that lift the fur or feathers away from the
skin.
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Blubber
Blubber is another form of insulation to reduce heat loss
from organisms living in water, such as the Australian
fur seal (Arctocephalus pusillus). This significantly
minimises heat loss.
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Blubber
 Another word or phrase that can be used to describe
blubber is:
There is no other word or phrase
Subcutaneous fat
Brown fat
Woo!
Noo!
Surface area to volume ratio
Surface area to volume ratio is an important structural
component of temperature regulation. Larger animals have
smaller surface area to volume ratios in comparison to that
of smaller animals.
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Common Wombat
 The common wombat (Vombatus ursinus) has a large,
compact body with relatively small surface areas from
which it can lose their internally produced heat.
Therefore, the wombat loses very little heat to its
surroundings, which is very useful in the cooler
months
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Colouration
Colouration of animals also
helps in temperature
regulation due to the fact
that dark colours absorb light
and associated heat. This
means that animals, such as
the diamond-backed python
can tolerate colder
temperatures.
Many desert animals are pale
in colour in order to avoid
absorbing heat from the sun.
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Physiological adaptations
 Physiological adaptations focus on inner body
functions.
 This includes changes to metabolic functions and
regulation of blood flow
Metabolic activity
Hibernation
Torpor
Blood flow
Countercurrent exchange
Metabolic activity
 The rate of metabolic activity can be
altered to ensure that an organism has
a better change of surviving
temperature conditions above or
below their tolerance range for
temperature.
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Hibernation
 Hibernation is an extended period of
inactivity in response to cold, where the
body temperature does not drop below
30°C but heart rate and oxygen
consumption drop considerably.
 Hibernation is a form of mild torpor and is
less intense, but may last for an extended
period of time
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Torpor
 A state of torpor is a short-term hibernation
where body temperature drops to much lower
than 30 °C and metabolism, heart rate and
respiratory rate decrease. This is accompanied by
a reduced response to external stimuli.
 Due to the fact that body temperature drops to
almost ambient temperature, metabolism slows
and energy can be conserved.
 Animals do not eat or drink during this state.
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Common wombat (again!)
 The common wombat slows its metabolism down to a
third of its normal metabolic rate on hot days,
particularly when sheltering in its burrow. This is a
useful strategy as wombats do not have sweat glands
to assist in heat loss.
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Regulation of blood flow
 Regulation of blood flow can increase or decrease
heat loss to surroundings.
 Since blood carries heat and usually the body
temperature of an organism is higher than that of its
surroundings:
Vasodilation of capillaries near the skin surface
increases the amount of heat lost to surroundings
Vasoconstriction of capillaries near the skin surface
increases the amount of heat lost to surroundings
Woo!
Noo!
Regulation of blood flow
 This mechanism is used
in the red kangaroo and
the bilby.
 The bilby has an
extensive network of
capillaries throughout
the ear which aids in
releasing heat to its
surroundings
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Countercurrent exchange
 Countercurrent exchange allows the warm blood in
arteries (from heart to the extremities) to heat the
cooler blood in the veins coming back from the cold
extremities, before the blood is returned to the heart.
 The Australian fur seal (fins) and the platypus (feet)
are examples of Australian animals who have this
physiological adaptation.
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Platypus
In the pelvic region of the
platypus, there is a network of
intertwined veins and arteries.
Cooled blood returning from the
legs and tail of the platypus
absorbs the warmth from the
blood being pumped from the
heart.
This allows the cold blood returning from the limbs with a large
surface area that is exposed to the cold water to be warmed so as
to not lower the internal core temperature.
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If you weren’t confused enough
already...
 Some adaptations are a combination of
structural, behavioural and
physiological features.
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Red kangaroo
 The red kangaroo licks its paws to cool itself down
through evaporation of water on its skin.
 The location of many blood vessels near the surface of
the skin in the forearms and paws is a:
Behavioural adaptation
Structural adaptation
Physiological adaptation
Woo!
Noo!
Red kangaroo
 The dilation of arterioles in hot conditions to direct
more blood flow through these vessels is a:
Behavioural adaptation
Structural adaptation
Physiological adaptation
Woo!
Noo!
Red kangaroo
 The licking activity to impart saliva for evaporative
cooling is a:
Behavioural adaptation
Structural adaptation
Physiological adaptation
Woo!
Noo!
THE END