Answer:
You can tell by which animals are at the top of the food chain.
Step-by-step explanation:
You can tell this because if you count all the biomass below the animals at the top of the food web (which eat all the biomass below it), there is much more biomass below these animals (the ones at the top of the food chain), than any other animal below it. For example, if the rat ate a grasshopper it will receive its biomass, but if the python then eats the rat, then the python will be getting the biomass of the rat and the grasshopper, compared to the rat just getting the biomass of the grasshopper. So since there is much more biomass below the animals at the top of the food web, this means that the animals at the top of the food web receive the most biomass (when they eat the animals below them) out of the whole food web individuals.