1.  Organisms tend to increase geometrically

        a.  Each adult individual produces more than one offspring.
        b.  Confirmed by empirical observation

2.  A finite amount of resources is available to support a population.

3.  Individuals that do not aquire a minimum amount of resources fail to reproduce.

4.  Population size can not increase indefinitely.

       a.  Consequence of (2) and (3)
        b.  Ceiling on population size is carrying capacity, K.

5.  Once K is reached, more offspring will be produced than can be supported by available resources.

        a.  Consequence of (1) and (4).

6.  Some individuals do not obtain enough resources to grow and reproduce.

            a.  There is competition among individuals for resources—the "struggle for existence".
            b.  Some individuals fail in that competition.
            c.  Consequence of (2) and (5).

7.  Some individuals are better equipped for competition to obtain resources, and they are better equipped
       because of their genetic makeup.

        a.  Does not follow from any of previous statements.
        b.  Open to empirical verification.

8.  Individuals that are better equipped for the competition to obtain resources are more successful at
       reproducing.

    a.  Follows by definition from (7).

9.  Traits that confer improved competitive ability have greater representation in the next generation.

        a.  Follows from (7) and (8).
        b.  This is evolution.
 

                        [ Bio 120 Handouts | Bio 120 Home Page | Department of Biology | Duke University ]