Surface Area to Volume Ratio

If we take a look at smaller organisms, something to take notice of is that they can use diffusion to exchange substances with their environments.
If we look at humans, we need specialised systems for transport via the heart and blood vessels, like our intestines and lungs for breathing and expelling waste.

The single-celled organisms have to constantly be doing chemical reactions to survive, like gathering amino acids, glucose and Oxygen, and getting waste like carbon dioxide out.

Everything has a Surface area to Volume ratio, for example, a cell has a higher surface area to volume ratio than a cow, as when organisms increase in size, the surface area to volume ratio decreases.

Now calculating this kind of thing is a bit confusing for organisms, instead we will use a small 1cm by 1cm by 1cm cube.

To calculate the surface area, you must first get the length and the width of one face, and multiply them together, so 1cm*1cm is 1cm^2 or 1cm squared, then you multiply it by 6 because a cube is six-sided, to get 6cm^2.
To get the volume of the cube, you need to multiply three values, which in this case is 1cm*1cm*1cm, to get 1cm^3, or 1cm cubed.
So at the end it has a ratio of 6:1, because it is six times bigger than the volume of the cube.

Now if we take another cube and instead of it being 1cm*1cm*1cm, it is 2cm, first we take one face of the cube and multiply it by its height and width (2cm*2cm), then which gives us 2cm^2, then we multiply it by six because six-sided cube then we get 24.

Then the volume is 8, by multiplying all the values 2cm*2cm*2cm, giving us 8cm^3 or 8cm cubed, so putting it into an equation would give a ratio of 24:8, which we can simplify by dividing both equations by 8, which gives us a ratio of 3:1.