A- TYPES OF TEMPERATURE REGULATION
1- The cat, human and platypus could be described as true endotherms, as they all maintain a relatively constant internal body temperature that is independent of the external temperature. As the environmental temperature rises from 5C to 40C, the humans body temperature remains constant, the cat’s and the platypus’ increases by around 3▫C.
2- The lizard and echidna are ectotherms as their body temperature fluctuates according to the temperature of the external environment. The lizard’s body temperature rises by 25C and the echidna by 10C as the external temp rises.
3- All animals are either clearly ectotherms or endotherms apart from the echidna. Although the body temperature of this animal increases with the external temperature, it does not increase as clearly as the lizard’s. An explanation for this could be that the echidna maintains a higher level of ability to control over internal temperature than the lizard, which has a very limited ability to do so.
4- All enzymes and other molecules function within a limited temperature range. Unless the body temperature is maintained at these optimal conditions, the rate of enzyme-catalysed reactions decreases and the organism will not function properly.
B- SOME METHODS OF MAMMALIAN TEMPERATURE REGULATION
Observation Explanation Type of adaptation
Echidna’s living in cold regions hibernate during the winter Hibernation is used to keep the animal’s body temperature constantly warm by removing itself from the cold environment Behavioural
Your skin often looks quite flushed on a hot day This is due to the vasodilation of arterioles Physiological
Many Australian marsupials salivate and lick their fur on hot days Saliva is used as a way to cool down, much like sweating Behavioural
Whales have a thick layer of blubber under skin This layer provides insulation from the cold water Structural
You tend to feel cooler on a hot dry day then on a humid day of same temperature This is as the moisture in the air on humid days does not allow the evaporation of sweat to keep body cool Physiological
A small mammal, with same body temp as a larger mammal looses more heat than the larger This is due to the fact the small mammal has a larger SA:V ratio. More skin is in contact with the environment, compared to size, thus it looses more heat Structural
C- EXAMPLES OF AUSTRALIAN EDOTHERMS
5- The breathing rate remains constant from 0 – 34*C at a rate of 40 breaths per minute. When the external temperature increases from 34*C onwards the breathing rate increases rapidly from 40 breaths per minute to 160+, an increase of 400%.
6- In extreme temperatures potoroos will increase their breathing rate as a method of temperature regulation.
7- Another adaptation of the potoroo for temperature regulation is the fact that it is nocturnal. The animal “sleeps by day in a nest of vegetation”, thus sheltering itself from the heat of the day. It feeds and undergoes activities in the cool of the night.
8- This is a behavioural adaptation.
9- The graph shows evidence that echidnas enter a state of torpor. The sluggish inactive periods of torpor are seen where the body temperature is low at about 10*C. These periods of torpor are interrupted by large bursts of activity demonstrated by the body temperature increase to 30*C. This is consistent with the activity of an animal in a state of torpor.
10- An echidnas heart rate, oxygen consumption and overall metabolic rate when in torpor would be much lower that when the echidna was active.
11- Torpor allows the echidna to stay inactive during most of the cold winter months, meaning that they shelter from the cold. Levels of activity in the cold weather are kept to an absolute minimum for survival.
D- EXAMPLES OF AUSTRALIAN ECTOTHERMS
12- The kangaroo (endotherm) – A kangaroo has the ability to change the pattern of blood flow to allow cooling. This is a characteristic of many desert animals, who’s extremities are designed to help in heat loss. The Kangaroos forearm has a dense network blood vessels that dilate in hot conditions to increases the blood flow to the forearms, which allows the blood to come in close contact with the external environment, resulting in cooling of the blood. (NB: think SA:V ratio) The kangaroo also has behavioural adaptations to assist in cooling, such as licking forearms, which act like radiators for heat loss and sheltering from the sun. The light coloured fur also reflects the heat of the sun.
Locusts (ectotherm) – The locust relies mainly on sunbaking to raise and lower their blood temperature. In the early morning, locusts turn side onto the sun to present a large surface area and thus absorb as much heat energy as possible. In the heat of the day however, they directly face the sun, minimizing the surface area and thus also minimizing heat absorption in the hottest part of the day.
13- Some disadvantages of being an ectotherm are –
*As cannot maintain constant body temperature, the day to day activity is greatly based on gaining or loosing heat energy according to changing conditions in the environment
* When environmental temperatures are low, the activity of ectotherms is also low as the metabolic rate is low
* The ability of endotherms to maintain constant body temperature allows for a broader geological and ecological distribution than that of ectotherms, who can often only survive in specific environmental conditions
Some advantages of being an ectotherm are-
*More efficient in aquatic environments as they are adapted to the constantly cold temperatures and thus there is no need to regulate body temperature.
There are a number of adaptations that both endotherms and ectotherms use to maintain a constant body temperature, many of which depend on the surrounding environment. There are three types of adaptations:
Structural- relates to the way an animal is built, eg circulatory systems, body size
Physiological- relates to the way an animal functions/operates eg. Production of hormones, sweating
Behavioural- relates to the way an animal responds eg hibernation, burrowing
A distinguishing feature between ectotherms and endotherms is that endotherms are able to regulate temperature using a feedback mechanism that involves the hypothalamus, which is a physiological adaptation. Ectotherms are unable to do this, so their adaptations tend to be mainly behavioural and structural.
Adaptations used to regulate body temperatures
TYPE OF ADAPTATION ENDOTHERMS ECTOTHERMS
Structural In water *blubber is used for insulation.
*thick fur of feathers. No adaptations needed
On land *in hot environments have large SA:V ratio to increase heat loss
*Fur and feathers provide insulation
*In hot environments have large SA:V ratio to increase heat loss
Physiological In water *secrete oil that coats fur/feathers. Insulates skin from water and prevents heat loss by conduction No adaptations needed
On land *Changing patterns of blood flow
*cooling via evaporation of water
Behavioural *Seeking shade, sometimes through use of burrows. *Sunbaking
*seeking shade through use of burrows
*being nocturnal, thus being active in cool of night.
*hibernation – lizards = torpor, insects = diapause.