How Does Evolution Happen?

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Objective

Students will be able to explain mutation, migration and genetic drift as driving forces behind evolution

Big Idea

Natural selection is not the only force behind evolution.

Hook

5 minutes

Before the students come in, I use the answers from the prior lesson's probe to create simple pie charts for each question. This can easily be accomplished in Google forms by using the response sheet from the probe, and clicking on Form>show summary of responses.

I share this with the students letting them know that, "This is what we believe as a class today", and that the purpose of most of the lessons that will follow is to make sure we all end up with certain unifying concepts we all agree on.

Introduction to the Mechanisms

8 minutes

I tell the students that the purpose of today's lesson is to explore how evolution happens, and proceed to show Paul Anderson's video Five Fingers of Evolution, a TEDEd video.

This video does a nice job of explaining the concepts, so that students can then explore them a bit more deeply in the readings that follow.

Explore

30 minutes

For the explore section today, I have prepared four readings for the students, and posted them on my Articles for teaching blog.

 

For this activity I use the jigsaw strategy, which allows one student in each group to become the "expert" in one particular aspect of the topic, and then teach it to the rest of the group. Students are asked to divide themselves into groups of four.

I explain that each member of the group is responsible for reading one topic (there are four readings), taking notes and report back to the group. I model the expectation by selecting one of the groups and stating

"Student 1 (identify him/her by name) will read Gene Flow, take notes on what Gene Flow is, how it works and have an example to help explain it to the other members of the group; Student 2  (identify him/her by name) will read Genetic Drift, take notes on what Genetic Drift is, how it works and have an example to help explain it to the other members of the group; Student 3  (identify him/her by name) will read Mutations, take notes on what Mutations are, how it works and have an example to help explain it to the other members of the group; Student 4  (identify him/her by name) will read Natural Selection, take notes on what Natural Selection is, how it works and have an example to help explain it to the other members of the group. Once everyone in the group has completed the reading, you will come together as a group and share with the team. Each member will have 5 minutes to verbally explain their section to their team" (SP8 Obtaining, Evaluating, and Communicating Information)

I then have students pick up the Driving Forces of Evolution Jigsaw note taking sheet, and explain how the front is where I expect them to take notes as they read, and the back is where they should take notes as they are listening/discussing with their team members. 

In a traditional jigsaw, students would first form expert groups that clarify their understanding through a discussion before sharing with the whole class or members of a group. However, I don't feel  always works as some students tend to sit back during the reading and wait for the expert group discussion before they actually begin interacting with the material. By knowing that they will be responsible for their topic without another student taking the leadership role, they are forced to take ownership of their own efforts, and continue to develop their skills to read and "present claims and findings, emphasizing salient points in a focused, coherent manner with pertinent descriptions, facts, details, and examples." (SL.7.4). In this video, you can see how this looks in the classroom as student "experts" teach their teams.

 

Note to teachers: You will notice in the student work (Genetic Drift SW1Mutation SW2Natural Selection SW3Gene Flow SW4) the big difference between the "expert" work-front page and what was recorded by the "learner"-back page. This is understandable since the learners rely on what the experts said to craft a quick summary. This lesson is followed by several experiences where all the students will delve deeply into each topic. What I see as a huge advantage in having this jigsaw introduction is that each table group now has an expert to rely on as they proceed through the different activities, who can then clarify concepts as the need arises.

Closure

5 minutes

To close this lesson, I post the following question on Edmodo.

Name one thing you are still thinking about as you leave the classroom today, AND why you are still thinking about it?

The "what" of this question reveals to me areas that might still be unclear, and the "why" allows students to briefly reflect on the learning process.