The Definition of Life:
Can the fertilized egg be included?

    When asking the question, "When does human life begin?" one first needs to define the properties that are characteristic of any living organism. A scientific and factual answer to this controversial question will separate the characteristics of living and nonliving organisms and then determine what category the fertilized egg falls into. An answer to the aforementioned question will answer the following question: Does the fertilized egg possess the same properties of all living organisms?

    Cleveland Hickman, Jr., Larry Roberts, and Allan Larson (1997) begin to provide answers to these questions. "Although we do not force life into a simple definition, we can readily identify the living world and separate it from the nonliving. Many remarkable properties have arisen during life's history and are observed in living forms in various combinations. They clearly identify their possessors as part of the unified historical entity that we call life."

    According to Hickman, Roberts, and Larson (1997), any living organism will meet the following seven basic properties of life:

    1) Chemical uniqueness. Living systems demonstrate a unique and
        complex molecular organization.
    2) Complexity and hierarchical organization. Living systems
        demonstrate a unique and complex hierarchical organization.
    3) Reproduction. Living systems can reproduce themselves.
    4) Possession of a genetic program. A genetic program provides fidelity
        of inheritance.
    5) Metabolism. Living organisms maintain themselves by obtaining
        nutrients from their environments.
    6) Development. All organisms pass through a characteristic life cycle.
    7) Environmental reaction. All animals interact with their environment.

 

    (A photograph of a fertilized egg.)

      An analysis of the fertilized egg must be made to determine if the fertilized egg and the resulting zygote, embryo, and fetus can all be classified as living organisms. Do these entities meet the properties seen in all living organisms?

    1) Chemical Uniqueness. Fertilized eggs possess their own unique DNA
        from conception.
    2) Complexity and hierarchical organization. Hickman, Roberts, and
        Larson (1997) explain that the most basic unit in the biological
        hierarchy is the cell. The cell holds the properties of living organisms,
        and cells can be manipulated in the laboratory and can be reproduced,
        whereas nonliving elements cannot. Therefore, the fertilized egg would
        meet this criteria, although it would be a more basic unit of the
        biological hierarchy.
    3) Reproduction. Francis Beckwith (1994) observes that the zygote
        possesses two different methods of reproduction: cell reproduction and
        twinning. According to Beckwith (1994), twinning is "a form of asexual
        reproduction, which can occur after conception."
    4) Possession of a genetic program. Francis Beckwith (1994) confirms
        that from conception, the fertilized egg has "its own unique genetic
        code." The 46 chromosomes present at conception provide all of the
        genetic information that will ever be needed.
    5) Metabolism. Francis Beckwith (1994) confirms that from conception,
        the fertilized egg meets the requirement of metabolism.
    6) Development. Hickman, Roberts, and Larson (1997) state,
        "Development describes the characteristic changes that an organism
        undergoes from its origin (usually the fertilization of the egg by sperm)
        to its final adult form." Thus, although the fertilized egg will take on
        different forms throughout its life cycle, the development of life begins
        at conception.
    7) Environmental interaction. The entity in the womb interacts with its
        environment in many ways. Kicking and jumping are both examples.
        In addition, research has shown that the fetus can be soothed by music
        and can recognize the voice of its mother.
 

    The fertilized egg, from the moment of conception, meets each of the properties that have been found to determine if an organism can be classified as living. Based on this definition, life begins at conception.
 

  Return to the Biological Facts.


  This page was made by Christina Rutten, a student at  Wayne State College, on April 20, 1999. If you
                have any questions or comments, please e-mail me at c_rutten@hotmail.com.