Nerves are cells that can detect any type of pressure, movement, or anything of that nature. If we didn't have nerves, we couldn't feel pain. If the nerves in a foot are damaged, you wouldn't feel the pain of it being burned.
The physiological process which explains the principles is mitosis b.
Overproduction - An organism gives birth to too many children
Genetic Variation - The offspring each have genetic differences in appearance, behavior, etc
Struggle to Survive - Offspring must fight in order to gain essential resources (food, water, mates, etc)
Successful Reproduction - Organism produces offspring with beneficial adaptations that aid in survival
Yes, protists have cell walls.
Protists cell walls are made of composed cellulose, protein strips , and silica
For some protists, we can even found components like pectin on the cell walls
hope this helps