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.
Why Do People Faint? Fainting is pretty common in teens. The good news is that most of the time it's not a sign of something serious. When someone faints, it's usually because changes in the nervous system and cause a temporary drop in the amount of blood reaching the brain. When the blood supply to the brain is decreased, a person loses consciousness and falls over.