Think of it like this. Horses do a LOT of galloping, which is hard on the feet! Hooves are a physical ADAPTATION, so that the horses won't experience pain on their journeys. They're hard, so that the horses don't feel the ground nearly as much. Now, mountain goats travel over rough terrain, with sharp rocks and steep inclines. Again, it's really easy for them to get hurt strutting around the mountains, so they evolved hard hooves to protect their feet.
Hydrogen and hydroxide ions
please see the attached images. Hope this helps you.
Answer - Viruses are not made out of cells, they can't keep themselves in a stable state, they don't grow, and they can't make their own energy. Even though they definitely replicate and adapt to their environment, viruses are more like androids than real living organisms.