Question

why do most of the food chains contain four steps

Answer 1

This is because when energy transfered from one organism to other it keep reducing.So the plants,herbivours,carnivorus and omnivorous interdepend on them.But the energy in plants is more than that of herbivoures,which inturn is more than in carnivourous.

Answer 2

yes most of the food chains consists 4 steps like
GRASS-------RABBIT--------FOX--------TIGER
because in an ecosystem the food chains are as followed
PRODUCERS---PRIMARY CONSUMERS---SECONDARY CONSUMERS---TERITIARY CONSUMERS.