Lesson 4: Mechanisms of Evolution
What We're Going to Learn and Why it Matters
So Darwin's critics are all like, "Oh, yeah, Mr. Darwin! If this whole natural selection thing is so cool, then how do you explain the absurd air sac growing out of the chest of a frigatebird? What advantage could that possibly have? Or how about that fossil of an Irish elk with a twelve-foot wide rack of antlers? You can't tell me there's an advantage to getting clothes-lined by tree branches all day. Or what about that giant crumb-duster growing out of your own face, Mr. Darwin? What possible advantage could there be to that?"
Now if this were politics, Darwin might have gotten defensive and tried to bolster his argument with some smooth talking points. (Or pretend to answer the question, but actually spend most of the time talking about his great work on coral reefs.) But Darwin was not a politician; he was the consummate scientist. So instead, he said, "You're right. That IS funny." And that line of questioning (in part) eventually led him to write a second book on evolution in which he expounded upon a whole other mechanism for evolution BESIDES natural selection. It turns out that there are other evolutionary mechanisms out there, and they are important to understand if you're going to explain the strange traits you see in the creatures around you. By the time this lesson is over, you should be able to identify examples of five different mechanisms of evolution or, alternatively, you should be able to provide examples of each of them. One of those five is natural selection. What are the other four? |
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Predict
(3:00 minutes)
What other mechanisms BESIDES natural selection might lead to a change in the allele frequencies in a population?
Answer on Google Classroom.
What other mechanisms BESIDES natural selection might lead to a change in the allele frequencies in a population?
Answer on Google Classroom.
Introduction to the Bean Model
(10:00 minutes)
Mr. Lord will demonstrate how this model works using natural selection as an example.
Mr. Lord will demonstrate how this model works using natural selection as an example.
Small Group: Building Understanding Discussion
(35:00 minutes)
In your small group, complete the assignment, "Other Mechanisms of Evolution". In it, you will use beans and Petri dishes to represent alleles and populations so that you can show how different processes might lead to evolution.
In your small group, complete the assignment, "Other Mechanisms of Evolution". In it, you will use beans and Petri dishes to represent alleles and populations so that you can show how different processes might lead to evolution.
Whole Group Consensus Discussion
(20:00 minutes)
Describe five different mechanisms of evolution. Record your consensus in a Google doc that will be shared on our Classroom stream.
Describe five different mechanisms of evolution. Record your consensus in a Google doc that will be shared on our Classroom stream.
Individual Summary
(5:00 minutes)
Take a moment to post individually on Google classroom and reflect on your learning in this lesson. You may do this in several ways.
Take a moment to post individually on Google classroom and reflect on your learning in this lesson. You may do this in several ways.
- Summarize the five different mechanisms of evolution.
- Speak briefly about how this learning has changed your understanding of evolution.
- Reflect on how this knowledge might be important.
- List questions or confusions about this that still remain.
- Any combination of the above.