Animals have evolved ways of behaving which help them survive and reproduce in their habitats. 1. * Animals that others prey on are alert and always attentive in case they can see, hear or smell a predator. Those that don't get preyed on. 2. * Hungry predators are always alert to find prey, those that don't starve. Some animals do not behave in ways that help them survive and are killed off because only the fittest survive. Others don't behave in ways that help them reproduce and leave no offspring. See Charles Darwin, Richard Dawkins and Natural selection.