a organism requires food for survival & the decrease of something required by an organism has a negative impact on that organism 's survival / that organism 's ability ->  a decrease of food has a negative impact on organisms  a decrease of food has a negative impact on organisms & negative impacts on organisms / species will decrease the population of the organisms / the species ->  a decrease of food for an organism will decrease that organism's population  predators eat prey & if an organism eats something then that something is a source of frood to that organism ->  prey is a kind of food for predators  a decrease of food for an organism will decrease that organism's population & prey is a kind of food for predators ->  a decrease of prey will decrease predator  a decrease of prey will decrease predator & population is a measure of the number of a species in an environment -> a decrease of prey populations will decrease predator populations