Explain how living in a group, like these lions, increases the fitness of a
species.

Explanation: Rivalry

There is safety in numbers, and with that, they can run together more often without the fear of being attacked, and must push themselves to match others, therefor getting fit

it would be rhyolitic hope this

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: