Survival of the fittest

Survival of the fittest means that only the strongest or most capable animals will survive and have babies. This means that over time, only the animals that are the strongest or smartest will remain, because they are the ones who are able to find food, protect themselves, and find mates. Animals that are not as strong or smart may not be able to do these things and will die off, so that only the strongest animals remain. This is how animals get better over time.