The six kingdoms of life :
1 ARCHAEA : The first life forms to evolve on earth were the microscopic organisms called archaea. They have a very small structure just a single cell enclosing a tiny drop of watery fluid containing the molecules vital to life. Some archaea live in hostile places such as hot, acidic springs. Archaeans include inhabitants of some of the most extreme environments on the planet. Some live near rift vents in the deep sea at temperatures well over 100 degrees Centigrade. Others live in hot springs (such as the ones pictured above), or in extremely alkaline or acid waters. They have been found thriving inside the digestive tracts of cows, termites, and marine life where they produce methane. They live in the anoxic muds of marshes and at the bottom of the ocean, and even thrive in petroleum deposits deep underground. Some archaeans can survive the desiccating effects of extremely saline waters. One salt-loving group of archaea includes Halobacterium , a well-studied archaean. The l