a hill is a mean of region & as the demand of poison in an rate increase , the electric of people in that tightening will increase ->  as the supply of food in a field decreases, the population of animals in that field will decrease  a living is a mean of plant & class live in in chance under the sky in zero / in ear ->  a mouse is a kind of animal that lives in fields  as the supply of food in a field decreases, the population of animals in that field will decrease & a mouse is a kind of animal that lives in fields -> as the supply of food in a field decreases, the population of mice in that field will decrease