Answer:Process by which two organisms evolve structures and behaviors in response to change in each other over time.
If a plant species evolves a new defense against an herbivore, such an thorns or poisonous secretions, this induces a new pressure on that herbivore to select for different individuals, such as plants that remain tasty and readily edible.
In turn, these newly sought-after plants, if they are to survive, must overcome that new defense; in addition, the herbivores can evolve thanks to individuals that happen to have traits that make them resistant to such defenses