Mechanisms for Evolution

What is the Recipe for Natural Selection?

Performance Objective: Given correct information about the mechanisms of evolution, journals, and a posttest, students will correctly define migration, genetic drift, mutation, and natural selection and classify examples as fitting under these topics on a posttest as measured by earning at least three out of four possible points.  

Content: Journal Prompt:

"Write the following steps in the proper order:

• A. Snurfles produce more offspring than the Snurfle Islands environment can support.

• B. Snurfles that survive reproduce, sending their genes into the next generation of Snurfles.

• C. Some Snurfles do not survive.  Those that survive are better suited to the environment(s) in the Snurfle Islands. 

• D. There is increased competition among Snurfles for fruit (resources)."

Evolution Notes

Write the following notes in your the Evolution Notes Template or your journal.

Evolution = Change in species over time

Mechanisms for Evolution:

• Mutation

• Migration

• Genetic Drift (random chance)

• Natural Selection

View images and descriptions of all these mechanisms here. Watch the Harvard bacteria video for mutation.

Use the Evolution Notes Template to write in the information. 

Follow-Through Activities: 

The teacher introduces and then facilitates a rock-paper-scissors game that (loosely) models evolution. During the game, the teacher will introduce the different mechanisms by making changes to the game. For example, all students in a certain part of the room at the moment that the teacher indicates it will be buried by a volcanic eruption and thus reset back to the starting species thus (loosely) modeling genetic drift. Following the game, the class will discuss how each example from the game represents each different mechanism. Here are the instructions (see evolutionary tree here):  

The following body movements represent different stages of evolution:  

• Crouched close to the ground with your hand as a dorsal fin above your head is sharks, a species that branched off early on.  

• Crouched down but with your arms making swimming motions is lungfish.  

• Standing with your arms out to the side like newt legs is amphibians.  

• Standing with your arm as an elephant trunk is mammals.  

To play the game:  

• You have to find someone at the same level as you and challenge them to one round of rock-paper-scissors (everyone starts out as sharks).  

• Whoever wins gets to 'evolve' up into the next category, making their way to the most evolved species, where you stay until you lose.  

• If you lose a round, then you go all the way back to the beginning stage (sharks).  

• Occasionally some natural disaster (meteor strikes earth; wildfire; disease) could strike and everyone resets to shark.  

Debrief Questions:  

1. How easy was it for you to make it all the way to the most evolved state?  

2. Does this mirror what we see in the natural world? If yes, how, if no, why not?

3. After more experience playing the game, did you come up with some strategy that helped you win? What was it?  

4. How can having a strategy for survival be connected to the sophistication of some more developed species?  

5. How did it make you feel when a natural disaster struck?  

Note: Evolution does not always lead to better - it is just change over time. 

Lesson Plan Summary:  

The Mechanisms for Evolution Notes lesson involves students learning from a journal prompt, notes projected on the board, a video from Utah Genetics, and examples from University of California, Berkeley’s evolution resource, recalling information that was presented, and applying understanding of the mechanisms for evolution to new and interesting examples provided by the teacher during the rock-paper-scissors follow-through activity. Instructional strategies include the teacher providing spoken and projected visual notes about the lines of evidence supporting biological evolution, presenting interesting scenarios to help students apply their understanding, and facilitating a kinesthetic game to help students retain the information. These instructional strategies support the behaviorist learning theory in that they are focused on the delivery of information and the recall of correct information and the cognitivist theory in that they allow students to apply their understanding to new examples/situations. Writing and recalling information correctly is behaviorist, but students learned about mutations in a prior genetics unit and natural selection earlier in this unit, so some elements of cognitivism (students building their learning within prior mental frameworks) will also be relevant.