Answer:
Stomata – Stomata are pores in the leaf that allow gas exchange where water vapor leaves the plant and carbon dioxide enters. Special cells called guard cells control each pore's opening or closing. When stomata are open, transpiration rates increase; when they are closed, transpiration rates decrease.
The dog was conditioned to it. The unconditioned stimulus (food) triggered the unconditioned response (dog salivating). By ringing the bell before bringing the food, the bell (once a neutral, but now a conditioned stimulus) triggered the dog's salivation. The dog's response is a conditioned response because he learned to associate the bell with food.
