These fluctuations may also affect the predators that feed on these prey items, such as wolves, foxes and owls. These predators must either find an alternate source of prey or risk starvation and death. Ecological Succession. When changes to either abiotic or biotic factors affect an entire ecosystem, ecological succession occurs.
A temporary decrease in blood flow to the brain results in unconsciousness, or fainting. Many disorders, some of them serious, can cause this.
The most common causes of fainting are usually not signs of a more serious illness. In these cases, you faint because of: The vasovagal reflex, which causes the heart rate to slow and the blood vessels to widen, or dilate. As a result, blood pools in the lower body and less blood goes to the brain.