sentences: an animal requires warmth for survival & winter means environmental temperature decreases ->  animals must move to a warmer environment in the winter  animals must move to a warmer environment in the winter & migration is when animals move themselves from a cooler climate to a warmer climate for the winter ->  an example of migration is moving to a warmer climate in the winter  an example of migration is moving to a warmer climate in the winter & birds fly south for the winter -> an example of migration is birds flying south in the winter