In this piece of coursework, I will be investigating the problem of why large birds, for example Penguins, are found at the South Pole and smaller birds, for example Robins and Sparrows are found in the British Isles. My theory to explain these circumstances revolves around the theme of adaptation. Generally animals are well adapted to living in their surroundings. Due to this, animals living in cold regions, for example the South Pole, tend to be larger in size than those living in warmer regions, because the larger animals have to retain more heat in order to survive.
But how does being larger benefit these animals in keeping warm? There is obviously some relationship between the size of the bird and the amount of heat lost. While trying to discover this relationship I will experiment with flasks of different sizes, which will act as hypothetical model birds, as it would be unethical to experiment with live birds. There are three main ways in which heat can be lost. These are conduction, convection and radiation. I will talk about each of these: – 1. Conduction – This is the transport of heat by the collision of molecules. Molecules in a hot region move faster than those in a colder region.
When molecules collide, energy is transferred from the faster to the slower moving molecule. Conduction is greatest in animals when the surface of the animal is in contact with a solid or liquid of a different temperature. This is a main reason why an animal in contact with the snow would lose heat, however this loss is minimised by the presence of fatty adipose tissue beneath the skin of some animals. This does not conduct, and therefore greatly reduces heat loss. 2. Convection – This is the transfer of heat by currents of air. Hot air rises and cooler air sinks, setting up convection currents around relatively hot objects.
This is another means of the animal losing heat, but it is also minimised by prevention of these currents, for example by trapping air in a fibrous layer outside the skin. Fur in mammals and feathers in birds perform this function. 3. Radiation – This is energy that travels from one place to another as electromagnetic waves. Infrared radiation accounts for most of heat energy radiated and absorbed by animals. So now that I know how heat is lost, I am going to have a more detailed look at the other side of the story, the size of the object. I can almost definitely say that there is a connection between the size of the object and the heat lost.
However, talking about, “Size,” in general is quite imprecise, as it is possible to be talking about either of two measures – surface area or volume. Both these factors are going to be relevant in this investigation as the greater the volume of the body, the more heat will be produced, and the greater the surface area of the body the more heat will be lost. A good example of this is a radiator – which has a large surface area so that more heat can be given out, or lost. So I am now searching for a link between these two factors, which could have a relationship with heat loss.
I think that as we are comparing them, a ratio might be useful in these experiments. To investigate this idea further I will consider cubes, once again as hypothetical model animals. CUBE 1 Side – 1cm Surface area – 6cm2 Volume – 1cm3 Surface area to Volume ratio – 6 : 1 CUBE 2 Side – 4cm Surface area – 96cm2 Volume – 64cm3 Surface area to Volume ratio – 1. 5 : 1 CUBE 3 Side – 8cm Surface area – 384cm2 Volume – 512cm3 Surface area to Volume ratio – 0. 75 : 1 A hypothetical cube of side n cm :- CUBE 4 Side – n Surface area – 6n2 Volume – n3 Surface area to Volume ratio – 6/n : 1.