There are 5 stages of sleep. The first four are under NREM and the last stage is REM. At stage 4 of NREM, the person can have deep sleep and brains continuously producing delta waves. If the person was aroused at this stage the person will feel disoriented upon waking up. This is the last stage of NREM. This will be followed by the REM or the stage where there is rapid eye movement even when the eyes is still closed,
During ecological succession of an ecosystem new organisms begin to grow and the ecosystem begins to recover. This is the way ecosystems repair themselves after a disaster.
