What are the two categories of sleep in mammals and birds?
Q: What are the two categories of sleep in mammals and birds?
A: The two categories of sleep in mammals and birds are REM-sleep (rapid eye movement) and NREM-sleep (non-rapid eye movement).
Q: When does REM-sleep occur?
A: REM-sleep occurs at intervals throughout the night, with periods increasing in length during the second half of the night.
Q: Who discovered REM-sleep?
A: Nathaniel Kleitman and his student Eugene Aserinsky first discovered REM-sleep in 1952–53.
Q: What is the function of REM sleep?
A: The function of REM sleep is not well understood.
Q: How many stages are there for NREM sleep?
A: There are three or four stages for NREM sleep - Stage I (dozing), Stage II (light sleep), Stage III (deep sleep) and sometimes Stage IV (also deep sleep).
Q: How long do adult humans typically spend asleep each cycle?
A: Adult humans typically spend 90 to 110 minutes asleep each cycle.
Q: When did the trait of having both REM and NREM Sleep evolve?
A: The trait of having both REM and NREM Sleep evolved before mammals and birds diverged in their evolution, suggesting that it is an early and important feature among land vertebrates.
