Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Living versus non-living criteria
Name: jconner
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993


Question:
What is the criteria for living versus non-living? Is life functions (growth, reproduction, etc.) sufficient or must structure also (cells) be included?



Replies:
Yes, textbooks are vague as no satisfactory answer has been found. This is probably because we have not tried very hard as life on earth is easy to recognize. As we begin to study outer space, we may need a better definition so we can recognize the very different forms of life that may exist elsewhere. All life forms on earth have deoxyribonucleic acids or ribonucleic acids. These molecules store then information necessary to build the next generation, so as to make more nucleic acid. One could ask whether organisms are merely the means to making more nucleic acids, in the form of genes. Many people have included the criterion of cellular structure in the definition of life but I have never known why. All life depends on other life forms for their reproduction, but viruses are particularly needy. Philosophers have taken some stabs at more general definitions of life, unlike most biologists who are usually satisfied to be able to recognize earth life when they see it. One definition I like is that living things are those that require energy to reproduce; and this reproduction is accomplished with some errors (ie. mutations). These errors distinguish life from inanimate crystals that can grow on themselves. This answer addresses how to define a living species, but ignore the questions of how to determine if any one organism is alive at any given time. That is a different question and one of degree.

Jim Murray



Click here to return to the Biology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory