Lesson 6: Speciation
What We're Going to Learn and Why it Matters
OK. OK. So I'm starting to get this whole microevolution thing. I can see how different mechanisms can affect allele frequencies, how selective mechanisms (like natural, sexual, and artificial) can cause different kinds of change (directional, stabilizing, disruptive), and even how we can use mathematics to make predictions about these allele changes.
BUT . . . what about new species? Mr. Lord, we spent weeks going through all of those different kinds of creatures. How does changing the frequency of an allele from 0.30 to 0.70 in a population lead to that kind of diversity? Like the differences between a cardinal and a blue jay? Or between a chicken and a dinosaur? To answer those questions, we're going to need to take all of the microevolutionary ideas we've been working with and connect them to macroevolution, evolution writ large. And we will. By the end of this lesson, you'll be able to explain how new species might arise by developing a few new elements to our evolutionary model. In assessment, that might look like this: I give you a scenario with two species that recently evolved from a common ancestor, and you visually map the elements of the model as the basis for a short written explanation. |
Observe
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Death Valley is generally considered a terrible place to make a living. (No surprise there.) This is especially true if you're a fish. But, believe it or not, there are actually some spring-fed bodies of water in the valley. Each one is inhabited by its own unique species of pupfish. These pupfish are considered separate species, but they clearly share a common ancestor.
Also of note, the Devil's Hole pupfish is often credited as being the rarest fish in the world with a population of about 200 individuals and a range of a single big puddle in a wildlife refuge near Death Valley National Park.
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Predict
(3:00 minutes)
What "rule" can be used to determine whether these fish are actually separate species? What kinds of conditions would lead these fish to become separate species?
Answer on Google Classroom.
What "rule" can be used to determine whether these fish are actually separate species? What kinds of conditions would lead these fish to become separate species?
Answer on Google Classroom.
Small Group: Building Understanding Discussion
(35:00 minutes)
Complete the assignment called "How does evolution lead to separate species?"
In your answer, map elements of any of the following models that you think apply:
You'll also need to add new elements as well.
When finished, attach a picture of your work to the assignment on Google classroom.
Complete the assignment called "How does evolution lead to separate species?"
In your answer, map elements of any of the following models that you think apply:
- evolution
- microevolution
- different mechanisms of evolution (including details of natural selection and types of selection if appropriate)
You'll also need to add new elements as well.
When finished, attach a picture of your work to the assignment on Google classroom.
Whole Group Consensus Discussion
(10:00 minutes)
Start with a gallery walk of your colleagues' work. Choose one group's poster as the work from which you will build consensus.
As a group, build one explanation that all group members can buy into. Record revisions right on that group's poster.
Start with a gallery walk of your colleagues' work. Choose one group's poster as the work from which you will build consensus.
As a group, build one explanation that all group members can buy into. Record revisions right on that group's poster.
Individual Summary
(4:00 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 differences between directional, stabilizing, and disruptive selection.
- 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.
Practice
(Homework)
Complete the assignment called, "Speciation Problem Set".
Complete the assignment called, "Speciation Problem Set".
Consensus Discussion
(20:00 minutes)
Start with a gallery walk of your colleagues' work. Choose one person's as the work from which you will build consensus.
As a group, build one explanation that all group members can buy into.
Start with a gallery walk of your colleagues' work. Choose one person's as the work from which you will build consensus.
As a group, build one explanation that all group members can buy into.
Individual Practice
(8:00 minutes)
Return to the pupfish of Death Valley.
In the question on Google classroom, propose an explanation for how speciation occurred in this instance. Use the summary sheet called, "Speciation: How does microevolution lead to macroevolution?" Include the key elements of the model in your answer IN CAPS.
Return to the pupfish of Death Valley.
In the question on Google classroom, propose an explanation for how speciation occurred in this instance. Use the summary sheet called, "Speciation: How does microevolution lead to macroevolution?" Include the key elements of the model in your answer IN CAPS.
Group Knowledge Building Discussion
(10:00 minutes)
Return to the pupfish of Death Valley. Propose an explanation for how speciation occurred in this instance.
Return to the pupfish of Death Valley. Propose an explanation for how speciation occurred in this instance.