In the Classroom
What is Heat and How to Measure it
Show NASA video of the Sun’s energy: https://www.youtube.com/watch?v=2U3ucaVzRqQ
Show PowerPoint –The Sun, and its energy spectrum (TOOLBOX)
Engage in student discussion:
• Notice that short wavelengths contain the most energy,
• Long wavelengths have less energy.
• Make comparison to a stone thrown into calm water – ripples are closer together the nearer they are to where the stone entered the water and travel at a faster rate, than when they are further out in the pond. Here, the ripples become further apart and travel more slowly because they contain less energy.
• Heat is the particular wave-length energy band in the region called infra-red.
Using thermometers
• Temperature is a measure of how hot or cold something is; specifically, it is a measure of the average kinetic energy of the particles in an object, which is a type of energy associated with motion.
• The faster the particles are moving, the greater the average kinetic energy of the substance, the higher its temperature, and the warmer it feels.
We use instruments called thermo-meters (‘thermo’ – heat; ‘meter’ – measure).
How does a thermometer work?
• Glass thermometer. This consists of a liquid (usually mercury) in a narrow calibrated glass column, and relies on the principle of thermal expansion. The energy in the heat makes the particles (molecules) in the liquid move faster and bump into each other more. This forces the liquid to expand (upwards) in the column. The upwards movement can be measured by a process called standardisation. A scale on the column is marked at 0oC (centigrade) with the base of the glass column in ice (frozen water) and 100o C with the base in boiling water.
• Digital thermometer and probe uses a microchip. Equipment in (TOOLBOX)
• Dual Laser Temperature Gun. Equipment in (TOOLBOX)
Temperature Regulation In lizards – Demonstrating ‘Ectothermy’
Show PowerPoint – Lizards and Heat (TOOLBOX)
There is a fundamental difference between lizards and mammals (and birds), in that very little heat is produced when a lizard metabolises its food. In a lizard’s tissues, metabolism (when food is oxidised, and heat is produced) is not as developed as it is in birds and mammals.
• A slow rate of metabolism has the following effects:
• Less oxygen is taken in, which helps them to hold their breath for longer than a mammal.
• less food is eaten, which helps them to survive on less food than a mammal needs.
• less heat is produced.
• However, a dragon lizard’s metabolism is like ours and works best at a temperature of 37oC, called its Preferred Body Temperature (PBT), which explains why lizards have behavioural adaptations to raise their body temperature.
• These reptiles have been incorrectly called ‘cold-blooded’. They are more correctly termed ‘ectothermic’ (‘ecto’ – outside, ‘therm’ – heat)
Behavioural sequence of the Ornate dragon, as follows:
• Emerging at an air temperature of around 20 degrees Centigrade, a lizard adopts the characteristic position of basking. It lies flat on the ground with its back to the Sun, thus maximising the radiant heat.
• When its body temperature reaches its preferred body temperature (PBT) of 36.6 oC, the lizard is active and forages.
• When midday temperatures become maximal, the lizard retreats under its rock habitat, but will emerge in the afternoon to forage again.
• If the rock is still hot, and the lizard’s body temperature reaches 39.5 oC, the dragon stilts. It lifts its body and tail off the rock, stands on its heels, and points its head to the Sun, thereby reducing maximum rays to its body.
Heat avoidance in the Western Netted dragon (Ctenophorus nuchalis)
• This dragon lizard lives in sandy areas in the northern Wheatbelt where temperatures are hotter. Its habitat is a burrow, to which it retreats during the hottest part of the day.
• Its behavioural sequence to regulate its body temperature is similar to that of the Ornate dragon, except that it climbs (a bush, or a fence post) to avoid excessive heat.
• It also has a physiological adaptation to avoid excessive heat. The lizard pales the coloration of its skin by constricting superficial blood vessels, effectively increasing the reflectance of the skin (see Activity 8). This, in turn, reduces the amount of heat penetrating its body.
• If this lizard species is located, record as for the Ornate dragon above, noting its adaptive position.
Keeping Eggs at the Right Temperature
Using a burrow
• A burrow is used by a lizard to avoid lethal air temperatures, and for incubating their eggs at the right temperature. The sex of lizard hatchlings depends on the temperature in their incubation site (5).
• Dragon lizards must incubate their eggs within a temperature range of 28 to 32oC, to have an equal number of female and male hatchlings. Temperatures either below or above this range, change the sex of the hatchlings to mostly female. On evolutionary grounds, this is not a good result.
• In warmer regions, dragons dig a hole in a termite mound and lay their eggs inside the mound.
Using a mound
Malleefowl (Leipoa ocellata), as birds, maintain their body temperature between 39oC to 43oC; they are endothermic. However, they are large ground dwelling birds, and do not put their eggs in a nest. Instead, they build a mound to incubate the eggs at 33 oC to ensure successful maturation.
Egg incubation for malleefowl is an extended activity.
• In the breeding season, the female lays an egg every 4 to 8 days until a litter of 15 to 24 eggs is deposited. Incubation time for each egg to hatch as a chick is about 2 months.
• Thus, laying an egg each 8 days, to reach a clutch of 24 eggs, spreads egg-laying over some 6-7 months. Maintaining the temperature for a further 2 months before the last egg hatches, requires 9-11 months of behavioural attention! How do they do it?
• Both male and female build and maintain the incubation mound, tossing up soil, leaves and twigs. The temperature of the mound is largely achieved by heat generated from the organic matter.
• Towards the end of the season, heat generated from litter fermentation becomes low, and heat from the Sun becomes important. The male bird takes advantage of the warm ground around the mound, heated by the Sun’s rays. The temperature sensitive cells in his beak act like a ‘thermometer’ (a morphological adaptation) and test the temperature of the soil surrounding the mound.
• The male ‘tosses’ warmed soil onto the mound, effectively keeping constant the temperature around the eggs.
Watch a Malleefowl in action at:
Pale form of C. nuchalis Travis Reeder
Temperature graph inside and outside a burrow at Shark Bay
Activity
Demonstrate Heat Absorbance and Reflectance, Using a Digital Thermometer:
MATERIALS
• Two containers of equal size and containing equal volumes of water
• Wrap one bottle in white paper and the other in black paper
• Digital thermometer See Equipment in TOOLBOX
METHOD
1. Predict which container will have the warmer water (black or white).
2. Set up the experiment, using 2 bottles of equal size and with glass of equal thickness and colour.
3. Fill each bottle with equal amounts of water.
4. Wrap one bottle in white paper and the second bottle in black paper.
5. Place the bottles in full sunlight for a minimum 2 hours.
6. Using a digital thermometer, insert the probe into the water of each bottle in turn, measuring the temperature every 30 minutes.
7. Allow the meter to return to a base-line level before inserting the probe into the second bottle.
8. Record the temperature over time in each container.
9. Write up, concluding the reasons for the result.
Time | White cover | Black cover
30 minutes | oC | oC
60 minutes | oC | oC
90 minutes | oC | oC
120 minutes | oC | oC
Reflecting Heat
Activity
Measure Temperature in Students - Demonstrating ‘Endothermy’:
METHOD
1. Revise the directions for use given with the temperature gun.
2. Each student measures a partner’s temperature as follows: Stand at least 3 metres behind the partner, and direct the temperature gun (with laser ON) at the back of the partner’s neck (narrnuk).
3. Hold the gun steady, read the temperature, and have the partner record.
4. Repeat twice, average the results, and record.
5. Discuss why it is important to standardise the distance each time the temperature is recorded.
6. For a Background reading, aim the temperature gun away from students and record the room temperature. Repeat, standardising the instrument between each reading.
7. Construct a Class Table on the screen and enter each student’s temperature.
8. Average the results.
9. Compare the average with the temperature in the classroom.
For discussion
• There is normal variation between human subjects. Temperature of students should vary around 35 to 37 oC. Other causes of variation in the recordings, may be due to a variable distance between the temperature recorder and the subject.
• The exercise demonstrates that all humans have much the same temperature, regardless of the temperature outside their body (in the classroom.) That is why they are called ‘warm-blooded’.
• Ask students what happens to a spark if they blow on it? It glows more brightly, burns faster, and gives off more heat. That is the result of the action of oxygen, and is similar to the action of oxygen in mammals, birds, and lizards, when they metabolise (or ‘burn’) their food.
• Do students know that all their energy comes from the food that they eat? In order to extract the energy from the food, oxygen is needed, which is why we breathe in air. Obtaining energy from food is called metabolism. The energy is used for muscles to work and for brains to think.
• How does the energy get to the muscles and brain? It is in the form of chemical energy and is transported in the blood.
• However, not quite all the energy is packaged as a chemical; some of it escapes as heat energy. This is the heat that keeps mammals and birds warm inside, at around 37 oC for most mammals, and between 39 oC and 43 oC in birds.
• Because we heat up from the inside, we are ‘endothermic’ (‘endo’ – inside, ‘therm’ – heat).
Activity
Observe and Record Summertime Behaviour in the Ornate Dragon (Ctenophorus Ornatus):
This activity requires local knowledge, a keen eye, and a quiet approach; you may need the assistance of an Aboriginal educator. Listen to information that the Aboriginal people may wish to share, such as stories about lizards, how they catch and prepare for eating, and where to find them.
The habitat of the Ornate dragon is under exfoliated rock sheets on a granite rock. There are about 2,000 exposed granites in the Wheatbelt, where lizards may still be observed. The granites are mostly on private land, but permission may be given for a class exercise.
MATERIALS
• notebook and pencil
• Infra-red (I-R) temperature gun
• low grade binoculars
• Copy of the activity cycle (above) of the Ornate dragon.
METHOD
1. Locate a lizard around mid-morning when it has emerged from its burrow or rock habitat and air temperature is around 25 - 28 oC.
2. Once spotted, focus the I-R temperature gun on the lizard and record its body temperature (BT).
3. Record the lizard’s behavioural pose. At this temperature, the lizard will be basking with its back to the Sun in order to reach its Preferred Body Temperature (around 37 oC).
4. Record the air temperature. To record the air temperature, the gun should be above the ground and pointing to the shade. If there is no shade, the student uses the shade of their body.
5. When the lizard’s (BT) reaches 37 oC , the dragon will be active and foraging on and around the rock, even though the air temperature may be less than 30 oC.
It is due to the lizard’s behavioural positions that allow it to raise its body temperature above that of the air temperature.
6. If air temperatures are 34 oC, or higher, this dragon may need to reduce its body temperature and stilt.
7. If air temperatures reach 40 oC, the lizard retreats to its habitat, under the rock, re-emerging when temperature falls in late afternoon.
8. Draw (or describe) the position of the lizard’s body in relation to the Sun’s rays, recording the air temperature, and add a short description of the particular behavioural adaptation and the selective force shaping it.
Activity
Record Temperature Inside and Outside a Lizard Burrow or a Malleefowl Mound:
Help students to design their experiment such that they will demonstrate the effectiveness of the burrow, or the mound as regulating the heat inside (insulation). They should consider recording temperatures at several times during the day and compare to environmental temperature.
METHOD
1. Locate a lizard burrow. Students may require the knowledge and assistance from the Aboriginal educators.
2. Using a digital thermometer (TOOLBOX), insert the probe 10 to 20 cm inside the burrow or mound, leaving the recorder in the open at the side.
3. Record 3 more temperatures: hold the probe in open air, on top of nearby bushes and on the ground outside the burrow or mound.
4. Measure temperatures 3 times during the day (if possible), and record, as in the Table.
5. Graph the results, with time of day along the x-axis, and temperature along the y-axis. There should be 4 lines; one line records air temperature, another on the ground surface outside the burrow, another on top of bushes and the fourth records temperature in the burrow.
6. Write up, concluding the effectiveness of the burrow as a protection against environmental heat, or maintaining optimal temperature for egg incubation.
Position of probe | Morning (9am) | Noon | Afternoon (3pm)
Outside air | oC | oC | oC
Ground surface | oC | oC | oC
Top of bushes | oC | oC | oC
Inside burrow/ mound | oC | oC | oC
Activity
Design a Vertebrate Animal, and its Adaptations that Help it to Survive in a Hot and Dry Region:
Your report will need to include the following information:
1. Describe your animal’s habitat and what it needs to survive. This should include what it eats, where it finds water, where it shelters or hides from predators, where it sleeps or nests
2. Describe your animal’s structural adaptations (its external features).
3. Describe your animal’s behavioural adaptations.
4. Explain how your animal’s structural and behavioural adaptations that help it to survive in its present environment.
5. Discuss how it might adapt to rising temperatures as the climate warms.
6. Discuss why the community living in and around the animal’s environment should consider their actions in order to protect the animal.
Warming up in the Ornate Dragon, Ctenophorus ornatus
Stilting in the Ornate dragon lizard, Ctenophorus ornatus
C. nuchalis on a fence post. photo IAN
