Temperature scales, heat transfer and air pressure
Week 11 · 2-3 Physical Factors and Their Effect on the Atmosphere (A): heat and the three temperature scales, conduction, convection, radiation, living through freezing and heat, atmospheric pressure, standard pressure, isobars, the barometer, pressure and the body · 3 lessons
2
Living through freezing cold and heat
Integrated Science Sec 1 Term 1, Unit 2: pp. 84–89
GoalDescribe how the wood frog, the icefish and the thorny devil lizard live through freezing cold and heat.
New words
antifreeze · a substance that stops ice crystals harming cellshaemoglobin · the red pigment in blood that carries oxygenadaptation · a feature that helps a living thing survive in its habitat
Explanation
Living things meet extreme temperatures with adaptations. The wood frog survives winter partly frozen: its breathing and heartbeat stop, and the glucose stored in its organs works as an antifreeze, so ice does not grow inside its cells. It does not die and come back; it survives a partial freeze. The icefish of the cold waters near Antarctica has antifreeze proteins in its blood and, unusually, no haemoglobin; it takes oxygen straight from the water (extra: cold water holds more dissolved oxygen). In the heat, the thorny devil lizard of dry deserts has tiny channels in its skin that collect moisture from air or sand and lead it to its mouth. These three show different answers to the same problem: keep the cells working in an extreme habitat. The icefish is a living fish, not a fish made of ice.
Animal
Problem
Adaptation
wood frog
freezing winter
glucose as antifreeze
icefish
icy water
antifreeze proteins, no haemoglobin
thorny devil
dry heat
skin channels collect water
Worked examples
Sort the adaptations by the problem. Freezing: wood frog glucose, icefish antifreeze proteins. Dryness and heat: thorny devil skin channels. This shows that an adaptation is a feature that fits the habitat.
Why does the icefish need no haemoglobin? Cold water holds a lot of dissolved oxygen and the fish is not very active, so its blood can take enough oxygen straight from the water. This is unusual: most vertebrates need haemoglobin.
A wood frog is frozen at −3 °C and later thaws. Is it right to say that it died and came back? No. Its heartbeat and breathing stopped for a time, but glucose protected its cells, so it survived a partial freeze.
Class activity
Design an animal, on paper. Choose a habitat (an ice field or a hot desert) and invent two adaptations that fit it, one for the body and one for behaviour. Draw it, label the adaptations, and explain in two sentences how each one solves a problem. Compare your animal with the thorny devil or the wood frog. Do not use real brand names or copy a book picture.
Practice
1
How does glucose help the wood frog in winter?
It works as an antifreeze that stops ice crystals harming the cells.
2
What unusual feature does the icefish’s blood have?
It has no haemoglobin (and it has antifreeze proteins).
3
How does the thorny devil get water in a dry desert?
Tiny skin channels collect moisture from air or sand and lead it to the mouth.
4
Is the wood frog dead while frozen? Explain.
No. It survives a partial freeze; its heartbeat and breathing stop but its cells are protected.
