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 NEXT

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. NEXT

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. NEXT

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 NEXT

Australian examples The water-holding frog (Cyclorama platycephala) can survive between temperatures of 3°C and 39°C NEXT

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. NEXT

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 NEXT

Examples of ectotherms From the list below select the ectotherms Plants Amphibians Mammals Reptiles Marsupials Birds Fish Invertebrates NEXT

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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. NEXT

Examples of endotherms From the list below select the endotherms Plants Amphibians Mammals Reptiles Marsupials Birds Fish Invertebrates NEXT

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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. NEXT

Central netted dragon Behavioural adaptation Structural adaptation 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

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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. NEXT

Eastern brown snake Diurnal Hibernation Nocturnal Being active at night is referred to as being: Diurnal Hibernation Nocturnal

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Eastern brown snake Behavioural adaptation Structural adaptation 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

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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. NEXT

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. NEXT

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. NEXT

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. NEXT

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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. NEXT

Mountain pygmy possum The mountain pygmy possum (Burramys parvus) lives above 1400 metres in the alpine regions of south-eastern 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. NEXT

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. NEXT

Mountain pygmy possum Behavioural adaptation Structural adaptation The mountain pygmy possum has short legs, a round body and small ears. This is an example of: Behavioural adaptation Structural adaptation Physiological adaptation

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Adaptations analyse information from secondary sources to describe adaptations and responses that have occurred in Australian organisms to assist temperature regulation NEXT

Adaptations Adaptations are characteristics that increase the survival and reproductive chances of an organism in its environment. NEXT

A variation that arises in individuals and have a genetic basis 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

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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. NEXT

Survival of the fittest Adaptations Natural selection is also known as: Flight or fight Survival of the fittest Convergent evolution

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Adaptations Behavioural Structural Physiological Adaptations are divided into three major categories. Behavioural Structural Physiological

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 NEXT

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. BACK

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. BACK

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. NEXT

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. NEXT

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. NEXT

There is no other word or phrase Blubber Another word or phrase that can be used to describe blubber is: There is no other word or phrase Subcutaneous fat Brown fat

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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. NEXT

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 BACK

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. NEXT

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. BACK

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 BACK

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. NEXT

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. BACK

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

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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 BACK

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. NEXT

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. NEXT

If you weren’t confused enough already... Some adaptations are a combination of structural, behavioural and physiological features. NEXT

Red kangaroo Behavioural adaptation Structural adaptation 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

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Red kangaroo Behavioural adaptation Structural adaptation The dilation of arterioles in hot conditions to direct more blood flow through these vessels is a: Behavioural adaptation Structural adaptation Physiological adaptation

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Red kangaroo Behavioural adaptation Structural adaptation The licking activity to impart saliva for evaporative cooling is a: Behavioural adaptation Structural adaptation Physiological adaptation

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