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.
Unexplained fainting spells need to be evaluated by a doctor. You can check your heart rate by taking your pulse. Many prescription and nonprescription medicines can cause lightheadedness or vertigo. The degree of lightheadedness or vertigo that a medicine causes will vary.