Pyramids.....

I kind of missed this bit out so this will only be really short!

Pyramid of numbers have limitations and you can get inverted pyramids so ecologists started to use biomass.....
Then a pyramid of energy was developed:
- collect organism
- burn in calorimeter
- calculate how much energy is released per gram

BUT, pyramids of energy have limitations too
- provide only a snapshot at one moment in time
- populations fluctuate over time, and this cannot replicate those changes
- gives a distorted idea of time efficiency of energy transfer

Instead, therefore, we look at the rate at which energy passes through each tropic level - so essentially productivity

- how much energy (in kJ or MJ) is available........
                 ......... per unit area (m2)......
                                 ......... in a given time (year)
e.g 54 000kJm-2year-1