Biology research - how animals area adapted to cold environments.

by khadze3 (student)

Khadeja Wodud 10Q

Surviving the cold

If an animal or plant is to survive it must be able to fit in with the environmental conditions which occur in its habitat. This fitting in is called adaptation. Every living thing is adapted to enable it to cope with a particular habitat’s environmental factors such as the air, water, soil, light and temperature. Polar bears and penguins never bump into each other. This because polar bears live only in the Arctic (the North Pole) and many species of penguins is found only in the Antarctic (the South Pole). Both animals are highly adapted for living in the coldest places in the world.

It is vital for a mammal, being a ‘warm-blooded’ vertebrate, to keep warm in order to maintain its body at a constant temperature. If it cannot do this it will die. The Arctic is the coldest place inhabited by land mammals and these have very thick fur, which insulates the body by trapping air. They also have a layer of stored fat under the skin which gives additional insulation.

Like many Arctic mammals, the polar bear has white fur made of hollow hairs, which traps and warms air. The polar bear has wide, large paws help them to walk in the snow. Ultra-violet light is funnelled from the sun down the hairs to the bear’s black skin, changing it into warmth. The dense undercoat is covered with an outer coat of long guard hairs. These help to keep the polar bear dry and warm while it is swimming.

The body shape and size of many cold climate mammals differ quite a lot from similar species living in warmer areas. Generally an animal becomes rounder and bulkier when its environment is very cold. Also its legs, ears and tail are shorter. These adaptations help to conserve heat. In short, a football-shaped animal would be warmest of all.

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Antarctic birds and mammals - penguins, whales and seals - are warm blooded animals and they maintain similar internal body temperatures to warm blooded animals in any other climate zone - that is about 35-42°C (95-107°F). They have to keep high body temperatures to remain active. Warm blooded animals in cold climates are pretty large, even the smallest Antarctic birds are on the large side and the smallest Antarctic penguin. The larger the animal, the smaller the surface-area: volume ratio and so the less relative area there is to lose heat.

In warm-blooded species, the relative size of exposed portions of the body decreases with decrease of mean temperature. An increase in exposed portions of the body (increasing surface area) also has several natural concomitants. Keeping mass constant, surface area is increased by assuming a more linear form--taller, with long, slender arms and legs. This is especially important for humans since heat loss from evaporation of sweat is greater than in any other animal, and evaporative loss is directly proportional to the amount of exposed surface area

Polar bears are well adapted for survival in the Arctic. They have:

A white appearance, as camouflage from prey on the snow and ice
thick layers of fat and fur, for insulation against the cold
a small surface area to volume ratio, to minimise heat loss
a greasy coat, which sheds water after swimming

Small animals have a large surface area to volume ratio. I.e. they have a large body surface compared to their body size so small animals lose heat easily. Large animals have a small surface area to volume ratio i.e. they have a small body surface compared to their body size so large animals don’t lose heat easily. Large animal, have small surface area to volume ratio so it does not lose too much heat.

For a single-celled organism (or a cell in a multicellular organism's body, for that matter), the surface is a critical interface between the organism/cell and its environment. Exchange of materials often occurs through the process of diffusion, in which dissolved molecules or other particles move from areas of higher concentration to areas of lower concentration (although some exchange is mediated by cellular mechanisms). This type of exchange is a passive process, and as a result imposes constraints upon the size of a single-celled organism or cell. Materials must be able to reach all parts of a cell quickly, and when volume is too large relative to surface area, diffusion cannot occur at sufficiently high rates to ensure this.

We'll begin with a reminder of some basic geometric formulae. The surface area and volume of a cube can be found with the following equations: and where S = surface area (in units squared), V = volume (in units cubed), and l = the length of one side of the cube.

The bigger surface area to volume, the quicker it will lose heat, as it has a bigger surface where the heat can rise and travel out from. If the volume is the same but the surface area is smaller, heat will stay in for longer as there is only a small area for the heat to escape from, meaning it has to go little by little.

A small organism, like an amoeba, has a large surface area: volume ratio, and so it can accomplish all the exchange it needs by simple diffusion across its body surface. However, a large organism, like a mammal, has a much smaller surface area: volume ratio, so it can not accomplish all the exchange it needs in this way. (A large surface area: volume ratio is preferable for carrying out exchange of substances). Such large organisms need special respiratory organs such as lungs for taking in oxygen and removing carbon dioxide.

Fick's Law shows how the factors which affect the rate of exchange interact

Rate of Diffusion: For Example

Calculating the ratio of surface area: volume for organisms

Look at surface area and volume values

Check they are in the same units

Divide the surface area value by the volume value. This gives you a figure which = answer

The answer: 1 is the ratio of surface area to volume.

e.g.

Surface area = 54 cm2

Volume = 27 cm3

Surface area to volume = 54/27 = 2

Teacher Reviews

Here's what a teacher thought of this essay

Stevie Fleming

3rd of Jan 2013

***This essay started well but spent rather too long discussing surface area to volume ratio in the second half. It appears to have been well researched with good listing of the references used. To improve All discussions or essays really need some kind of summary paragraph Surface area to volume ratio is very important but discussing how this is important at the cellular level is not really relevant to the title. Add some information on behavioural adaptations to the cold such as migration, hibernation and huddling. Do not forget that a large number of Arctic/ Antarctic creatures are marine and 'cold blooded'. How are they adapted to life in very cold water? There also plants in the cold regions. How are these adapted? Since the title is 'Surviving the cold' these could be included.

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