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.
You come round after a few seconds and feel back to normal. Some people feel very tired after they've come round. Usually, fainting happens for a reason, like when you're in pain or have been standing for a long time in a hot place. Fainting happens because the brain needs a constant supply of oxygen.