We adapt to cold weather by putting on more clothing. This is an example of one definition
of the term, adapt. Unfortunately, students may apply this definition to evolution.
This results in the erroneous impression that evolution consists of individuals adapting to fit
changes in their environments . Evolution proceeds by selection occurring within populations
containing large numbers of genetically varying individuals.
Randomness and evolution
Variation is random, selection usually is not. Selection of favorable traits within a population
occurs when living things meet all the challenges presented to them. These pressures are not random,
but are determined by physical laws. Barring the occasional tree randomly falling on an organism, or
a volcano wiping out a population, selection is not random and evolution does not happen by chance.
Ancestor versus relative
When we fail to distinguish between a common ancestor and a relative we set our students up for confusion. You and your cousin are related. You share a common ancestor. You did not evolve from your
cousin. Similarly, humans and chimps are related, but humans did not evolve from chimps any more than
chimps evolved from humans.
Confusing evolution with development
Development is the process that occurs as a living thing grows up (ontogeny). Evolution is change
of form or behavior of a population over time (phylogeny).
Simple to complex
In viewing the entire history of life on Earth, it is true that the first life consisted of relatively
simple cells and that aggregation of cells led to larger organisms. However, the rule that living things
always become more complex is erroneous. Insects evolved from arthropods with more than six legs. Birds
and snakes have lost parts. Humans no longer have tails. The direction of evolution is often toward the
loss of parts or behaviorsbecoming simpler, not more complex.
Use of the word design may imply that living things are designed and there is a plan at work. Use of such terms structure and adaptation are
more appropriate. Example: How is an aardvark designed to eat ants? could
be replaced by, How is an aardvark adapted to eating ants? or, What structures and behaviors aid an aardvark in eating ants?