harming something has a negative impact on / effect on that something & disease has a negative impact on an organism ->  disease harms an organism  disease harms an organism & harming an organism can cause that organism to die ->  disease can kill an organism which causes it to die  disease can kill an organism which causes it to die & if an organism dies then the population of that organism will decrease ->  if an organism dies because of disease then the population of that organism will decrease  if an organism dies because of disease then the population of that organism will decrease & harming something has a negative impact on / effect on that something0 ->  if a large bird dies because of disease then the population of those large birds will decrease  predators eat prey & if an animal eats other animals for food , then the animal will be the predator ->  if an animal eats another animal then the animal will be the predator and the other animal will be the prey  if an animal eats another animal then the animal will be the predator and the other animal will be the prey & large birds eat small animals ->  large birds are predators to small animals and small animals are prey to large birds  large birds are predators to small animals and small animals are prey to large birds & as population of predators decreases , the population of prey will increase in an environment because predator eats prey ->  as the population of large birds decreases, the population of small animals will increase  if a large bird dies because of disease then the population of those large birds will decrease & as the population of large birds decreases, the population of small animals will increase ->  if large birds die becuase of diesease then the population of small animals will increase  if large birds die becuase of diesease then the population of small animals will increase & population is a measure of the number of a species in an environment -> if large birds die because of disease then the number of small animals will increase