Why do we sleep?
A recent study may have an answer to one of the greatest unsolved mysteries in science — what is the purpose of sleep? The work suggests it’s ___REALLY___ about making animals function more efficiently in their environments. ___SCIENTISTS___ from the University of California, Los Angeles, conducted a study of the sleep times of a broad range of animals. They discovered much variation. You may think it ___IMPOSSIBLE___ but some migrating birds can fly non-stop for up to 90 hours.
Pythons and bats are among the longest ___SLEEPERS___ at over 18 hours a day. Human babies need 16 hours and their health and intellectual ___DEVELOPMENT___ depend on sleeping properly. Most of us probably feel we need around eight hours sleep to function well. Some people have ___DIFFICULTY___ in getting enough sleep and this may lead to serious health problems.