The Origin of Life

• Life is a characteristic that distinguishes physical entities that do have biological processes, such as signalling and self-sustaining processes, from those that do not, either because such functions have ceased, or because they never had such functions and are classified as inanimate.
• Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria.
• The criteria can at times be ambiguous and may or may not define viruses, viroid’s, or potential artificial life as "living".
• Biology is the primary science concerned with the study of life, although many other sciences are involved.
• The earliest known life forms on Earth are putative fossilized microorganisms, found in hydrothermal vent precipitates, that may have lived as early as 4.28 billion years ago, not long after the oceans formed 4.41 billion years ago, and not long after the formation of the Earth 4.54 billion years ago.