Why do land animals need stronger bones and muscles than fish?

Land animals have to support their own weight against gravity, which fish don't have to.

In water, the surrounding water provides buoyancy, which helps to support the fish's weight. On land, animals have to use their muscles and bones to hold themselves up against the force of gravity, which is why they need to be stronger.

Land animals also have to be able to move around on land, which requires a different set of muscles and bones than swimming does. Fish use their fins to swim through the water, while land animals use their legs to walk, run, or climb. This requires a different set of muscles and bones that are adapted for these specific movements.

Finally, land animals have to deal with the impact of landing when they jump or fall, which fish don't have to worry about. When an animal lands on the ground, the force of the impact is transmitted through its bones and muscles. This can cause damage to the bones and muscles if they are not strong enough.

For all of these reasons, land animals need stronger bones and muscles than fish.