We may not see it, but infrared can be important:
We begin just outside the visible range of the spectrum. The item before Red in the spectrum is ‘Infra-red’. We cannot see it, but we can feel it. So it is included. It is what our skin tells us is a source of warmth – such as a fire, or candle.
Furry mammals and birds of the air
Make heat inside their outer wear.
As do a few fish and some plants.
The heat produces a radiance
With an infra-red quality
That our eyes do not see.
Special cameras see this radiation
And show how feathers give insulation.
Their coat of feathery things
Holds heat better than head or wings.
Helping those Emperor penguins
Survive freezing Antarctic winds.
Our first subjects are Emperor penguins. They live in the Antarctic, and have to deal with air temperatures as low as −40 °F. Then there are howling gales – a 40 mile-an-hour wind will make it feel 13°C colder. Most organisms lose too much heat and die. Birds and mammals are special because they produce heat internally, and use it to keep their bodies at a steady temperature. For us, that is 98.6°F (or 37°C). One reason that the penguins survive is because they produce heat. Even so, that is not enough. They have to keep the heat in. If not, they would run out of energy, be unable to sustain control of their own temperature, and would die. Penguins avoid the loss of heat in many ways.
Firstly, they have insulation. There is a thick layer of fat under the skin, and this keeps the heat in the body when the penguin is on land, or when it is swimming and looking for food. It prevents heat getting to the skin and out of the body.
The second part of their insulation is a thick layer of feathers. They work like thick winter coats, they stop the cold air getting to the skin and to other parts of the body where there is blood flowing.
Another mechanism to prevent becoming chilled is that penguins often huddle together in groups. Some on the outside have to contend with the wind, but others on the inside of the group are sheltered and can conserve heat. And, being nice guys, every now and then, the inner guys move to the outside and take on the task of intercepting the Antarctic blast, and the guys on the outside move to the inside and are given some relief.
Next: Penguins do not have much blood flowing to the outer parts of the body – especially feet, tail, and flippers. The result is that very little blood (and warmth) is exposed to cold. Not only does this stop temperature being lost, but it also means that chilled blood does not get to the middle of the body.
There are more tricks. One is that muscles that operate flippers and feet are located in the protected warm body, and only pull on the feet and flippers through strings (called ligaments). In that way, blood just needs to keep the muscles in the body warm, and does not have to flow to muscles in the flippers and feet.
A little behavioral trick is that when penguins are on the ice, they often rock, and stand with just their heels and tail on the ground. That is, they make sure that as little of their body as possible touches the ice.
In this picture, the colors look strange. They are created by a special kind of camera that can see infra-red radiation. The camera shows us where heat is being lost from the penguin. Purple and dark blue areas are the ones where almost no heat is leaving the body. But there is more loss from the bright (azure) blue, and increasingly more where there is green, yellow, red, and then white. This infrared camera is a useful tool for people who want to understand how organisms manage their heat.
While most plants cannot,
Some lillies do get hot.
Heat from a skunk cabbage is on show
Because it melts the surrounding snow.
Who can make heat?
Mostly, we think of birds and mammals as being able to make heat and to have warm bodies. But, they are not the only organisms to produce heat – the term is ‘thermogenic’. A number of Arum lillies generate heat inside their bodies. One is this skunk cabbage. The photograph shows how the snow around the emerging plants has been melted. And, some fish (tunas) are also able to make and hold onto warmth. With warmer bodies, the muscles work better and the tuna swim faster. This helps them to avoid slower predators. In the process of evolution, there has been a compromise between using their limited supply of energy in heating up their bodies; and dealing with the risk from predators.
And then there are bacteria. If you put your hand into a thick layer of leaves when they have been collected in the fall, they will often feel warm. Perhaps they steam when it rains or snows. This is because bacteria produce heat … although not inside their bodies.
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