Darwin’s Theory
Darwin’s book On the Origin of Species by Means of Natural Selection
appeared in November of 1859. Many people were deeply disturbed
by certain suggestions of Darwin’s theory, such as that humans are
related to apes, as Figure 5on the previous page suggests. But Darwin’s
arguments and evidence were very convincing, and his view that evolu-
tion occurs gained acceptance slowly from biologists around the world.
Darwin’s theory of evolution by natural selection is supported by
four major points:
Variation exists within the genes of every population or species
(the result of random mutation and translation errors).
In a particular environment, some individuals of a population
or species are better suited to survive (as a result of variation)
and have more offspring (natural selection).
Over time, the traits that make certain individuals of a population
able to survive and reproduce tend to spread in that population.
There is overwhelming evidence from fossils and many other
sources that living species evolved from organisms that are extinct.
280 CHAPTER 13The Theory of Evolution
Modeling Natural Selection
By making a simple model of natural selection you can
begin to understand how natural selection changes a
population.
Materials
paper, pencil, watch or stopwatch
Student name Trial 1 Trial 2 Trial 3
DDAATTAA TTAABBLLEE
2B 2C 3E 7B
Procedure
1.On a chalkboard or overhead
projector, make a data table
like the one shown below.
2.Write each of the following
words on separate pieces of
paper: live, die, reproduce,
mutate. Fold each piece of
paper in half twice so that you
cannot see the words. Shuffle
your folded pieces of paper.
3.Exchange two of your pieces
of paper with those of a
classmate. Make as many
exchanges with additional
classmates as you can in 30
seconds. Mix your pieces of
paper between each
exchange you make.
4.Look at your pieces of paper.
If you have two pieces that
say “die” or two pieces that
say “mutate,” then sit down.
If you do not, then you are a
“survivor.” Record your
results in your class table.
5.If you are a “survivor,” record
the words you are holding in
the data table. Then refold
your pieces of paper and
repeat steps 2 and 3 two more
times with other “survivors.”
Analysis
- Identify what the four slips
of paper represent.
- Describe what happens to
most mutations in this model.
- Identify what factor(s)
determined who “survived.”
Explain.
- Evaluate the shortcomings
of this model of natural
selection.
