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== Principles: What is life, information, and the universe? ==

=== What is life? ===

Despite the work of life scientists over several centuries, a definitive answer to this deceptively simple question has been elusive.&nbsp;Life’s diverse properties include the following:

#Life is complex and dynamic.&nbsp;All organisms are composed of the same set of chemical elements, primarily carbon, nitrogen, oxygen, hydrogen, sulfur, and phosphorus.&nbsp;Living processes, such as growth and development, involve thousands of chemical reactions in which vast quantities and varieties of vibrating and rotating molecules interact, collide, and rearrange into new molecules. 
#Life is organized and self-sustaining. Living organisms are hierarchically organized systems 
#Life is cellular. Cells, the basic units of living organisms, differ widely in structure and function, but each is surrounded by a membrane that controls the transport of substances&nbsp;into and out of the cell.&nbsp; 
#Life is information-based. Organization requires information. 
#Life adapts and evolves. All life on Earth has a common origin, with new forms arising from older forms.&nbsp; 

Key concepts<br/> • All living organisms obey the chemical and physical laws.<br/> • Life is complex, dynamic, organized, and self-sustaining.<br/> • Life is cellular and information-based.<br/> • Life adapts and evolves. &nbsp;

=== Genetic information ===

All living organisms are information-processing systems. Their ultimate source of information is encoded in the nucleotide base sequence of DNA.

=== Universe ===

A universe consists of a system and its surroundings.

=== Evolution ===

Evolution, the adaptation of populations of living organisms in response to selection pressure, is made possible by the capacity to generate genetic diversity through various forms of mutation, gene duplications, or the acquisition of new genes from other organisms.&nbsp;