Sleeping patterns develop gradually. Babies usually sleep for brief periods throughout the day. Only reptiles, birds and mammals really sleep. Most reptiles do not have sleep periods. Birds have very brief sleep periods.
Mammals have periods of dreaming sleep and slow- wave sleep.
Some mammals such as cattle sleep standing up, but can only dream while lying down. Fish and Amphibians have periods where they become less aware of their surroundings but do not sleep. Insects and spiders have daily periods of reduced activity but do not sleep. Without sleep you could become quick- tempered and lose energy. After 2 days without sleep long periods of concentration become hard.