Developing stomach ulcers during a prolonged period of stress exemplifies how stress can have a negative impact.

physiological

When we are under constant stress, our body will start expressing it with physiological responses. When the body realizes the presence of the stressor agent, sends signals to the hypothalamus, and it activates the sympathetic and hormonal responses to eliminate the stress.
The digestive tract is a part of the body very commonly affected by stress.

If you remove all the lions from the savanna it will lead to a increase of gazelle and a increase of cheetahs becasue of no competition