What fuels we get energy from by burning them. Natural gas
Petrol
Coal
Nuclear fuel

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.

What do transitional fossils best support?

Based on the data in the graphs do you think pepsin and trypsin are found in the same part of the body? explain your answer.