Lesson 3: Types of Selection
What We're Going to Learn and Why it Matters
We've looked at how variation can arise from different sources. But what about the other part of natural selection? What about the selective pressure that actually leads to change? Can that come in different forms as well?
In this lesson, you'll use a new model (called a distribution curve) to describe the effects of three different kinds of selection.
By the end, you should be able to take a scenario in which a trait changes in some population, model it with a distribution curve, and name the kind of selection that is occurring.
In this lesson, you'll use a new model (called a distribution curve) to describe the effects of three different kinds of selection.
By the end, you should be able to take a scenario in which a trait changes in some population, model it with a distribution curve, and name the kind of selection that is occurring.
Observe
Polygenic traits are traits which are controlled by more than one gene.
If all phenotypes of a polygenic trait provide an equal chance of survival, the distribution of these traits will fall along a normal distribution. The frequency is highest near the mean and decreases toward each extreme end of the range. |
Predict
(3:00 minutes)
How do you think this distribution might change when different types of selective pressure are applied?
Answer on Google Classroom.
How do you think this distribution might change when different types of selective pressure are applied?
Answer on Google Classroom.
Small Group: Building Understanding Discussion
(20:00 minutes)
In pairs or trios, complete the packet called "How do selective pressures affect phenotype distributions?"
In pairs or trios, complete the packet called "How do selective pressures affect phenotype distributions?"
Whole Group Consensus Discussion
(10:00 minutes)
As a group, come up with one explanation for each of the three scenarios that all group members can buy into. Record your explanation in writing in the class's Google doc and in pictures on the whiteboard.
As a group, come up with one explanation for each of the three scenarios that all group members can buy into. Record your explanation in writing in the class's Google doc and in pictures on the whiteboard.
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.