A grizzly bear and a polar bear show variation in species. This helps them survive better in their own environments.
Some snakes will survive longer than others if they have venom. If they have venom, they have a way of protecting themselves from predators, unlike the snakes that have no form of protection. This represents differential survival.
Squids lay up to 11 pounds of eggs, which shows overproduction of offspring. They lay these many eggs because there are many predators of squid, so if they lay more eggs, more of them are likely to survive.
Wolves and foxes have the same prey, which is rabbits. This shows selective pressures because they are competing for the same food. The predator that catches more rabbits will survive.
Stabilizing selection can be seen through the birth of babies. The baby needs to be just the right size because if it is too small it will be too cold and die. If the baby is too large, it will lead to growing issues and possibly death for both the baby and the mother. Only babies who have a stable weight will survive.