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Studying Living Organisms

Peter Rabbit Meets Charles Darwin

Jane Y. Meneray
Woodrow Wilson Biology Institute
1995


Target age or
ability group:
Freshmen or introductory biology.
Class time
required:
15-30 minutes.
Materials and equipment: None.
Summary of activity: This is a good way to get students thinking about evolution in terms of populations. In fact, this is a good way to sneak in the whole concept of evolution. The class follows a cartoon scenario of a rabbit population in which there is selection and a change of gene frequency. The students can receive copies of the scenario or the whole thing can be done on an overhead.
Prior knowledge, concepts or vocabulary necessary to complete activity:
Gene, allele, per cent, species.

Teacher Instructions

None, as this is a discussion. Several other concepts might arise, however such as general ideas concerning heat loss and conservation. One can also take the concept further, later in the curriculum and use it to discuss speciation by proposing what might happen if the rabbit populations were to come back in contact with one another.

Peter Rabbit Meets Charles Darwin
Here's the story: Imagine a happy rabbit population living on the bank of a river. The population varies in ear length.

Allele A is dominant and it codes for long ears. Allele a is recessive and codes for short ears.

If you count the alleles in the population below you will see that the alleles are equally distributed: 50%A and 50%a.

Suddenly (Oh horror!) an earthquake occurs , the river changes course and the rabbit population is split. Rabbits don't swim well and the populations are effectively isolated.

The allele frequencies in ear length remain the same, however. (Count them and see.)

The earthquake has disrupted things and the southern population migrates south in search of food and the northern population migrates north in search of food. The rabbits reproduce (that's what rabbits do best) and many generations pass. Things have changed, however. Now allele A (long ears) gives the southern rabbits a selective advantage: long ears mean more heat loss, less energy expended, more time for fun and greater reproductive success.

Dies pre-reproduction
A=75% a=25%
Now lets look at the northern rabbits:
Some climatic change has occurred and in the northern rabbits allele a is favored.

Short ears mean less heat loss, more energy conserved, more time for fun, greater reproductive success.

Dies. Pre-reproduction.

New gene frequencies
A=25%
a=75%

The gene frequencies have changed. Has evolution occurred?

Has speciation occurred? How could you tell?

On to Camouflage and Protective Coloration:
A Model of Natural Selection / Richard Filson

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