It is probable that all living species require sleep to some extent, but the definition of sleep varies between species. For example, when a fish or a shark goes dormant, although their brain is still very much active, zoologists can determine that they are actually taking a sleep period as we would understand it. Contrary to popular belief sharks do 'sleep'.
Plants and trees too require sometime away from daylight and will �close� themselves up for a little kip, often in the evenings. This is called nyctinasty and for botanists, quite a fascinating subject. Of course some plant species including our house plants can take more daylight exposure than others but still nevertheless catch a little shut-eye now and again.
The extent of sleep thus varies as much between humans (Baroness Thatcher only required 5 hours sleep a night when she was PM) as it does between the plant and animal kingdom. Giraffe�s only need to sleep for about 2 hours in any 24 hour period, and sufferers of Morvans syndrome go for several months without sleep with no adverse effects.
All that has made me rather slee_