Why are the organisms at the top of food chains fewer than those at the bottom?

Question

For example, why are there hundreds of daphnia in a creek but only two water spiders?

Answer 1

because they are being eaten by those on the bottom: Shrub (Top, Producer) --> Cow --> Human --> Decomposers (Baceria, fungi)  

Answer 2

Because they are larger creatures and require more resources to survive. Their environment can only support so many of them.  

Answer 3

Because the things on top eat the things on bottom.  If there were more of the things on top, they would eat all the thing on bottom, then starve, and there would be no more of either.

Wolves eat rabbits, right?  Well if there were more wolves than rabbits, they would eat all the rabbits.  Then there's no more rabbits, and nothing left for the wolves to eat.  Then the wolves starve and there's no more wolves or rabbits.

In order for a sustainable balance to be met, there must be more prey than predator.

Answer 4

They usually have to eat more from the step below to survive, so naturally there will be less. If there were more organisms at the top, and let's say they all eat two organisms from the lower step, then the food supplies will go down and the population will decrease until the prey are bountiful enough to sustain the predators.