for the most part, plants and animals live in either a salt water environment or a fresh water environment, not both. Explain this using the principles of diffusion

Plants and animals that live in fresh water have more amount of salts in their bodies as compared to the fresh water. Hence, water enters into the plant or animal cell by the process of diffusion. As diffusion is the movement of particles from a high concentration to a low concentration, water will move in and excess salts will move out. Hence, these kinds of plants and animals will live in fresh water for most time of life.

On the contrary, plants and animals that live in salt water environment will uptake salts from the water through diffusion, as the amount of salts will be more outside then inside the cell. Hence, these kind of plants ansd animals will live in sea water for most of their life as they are adopted to the salty conditions.