Answer:
Animals detects changes in the environment with body parts called sensory organs( like eyes, ears, and noses etc)
Step-by-step explanation:
Many animals can sense tiny vibrations in the environment and use those to find prey or to detect predators. So for example, if there were so many preys in an environment, and an animal can move freely without getting caught they can sense that changes has happened in the environment that must have caused the predators to move away.
Hope this helps :)