Introduction to Convergent Evolution
1 Hook/Attention Getter: Squirrels and Sugar Gliders
This lesson opens with an activity to get students' attention. I let them know that I'm going to show them some photographs of two different animals, the Sugar glider (Petaurus norfolcensis) and the Northern flying squirrel (Glaucomys sabrinus). I ask them to make a few notes about what they can observe about each animal's appearance and, if possible, behavior. I use the slideshow feature on the ArKive site so that they aren't yet reading the text.
Students will observe that these animals appear to be very similar in both outward physical appearance and what they are doing in some of the photographs (gliding).
Next I will ask students where they think these animals live. I give them a moment to think about it and then have them discuss it briefly in table groups:
Where do you think the Sugar glider lives?
Where do you think the Northern flying squirrel lives?
I circulate and and listen to students conversations about these animals habitat. The types of connections they make will guide conversations I have with students in later parts of this lesson.
Students may think that these animals are very closely related and/or live in the same place based on the characteristics they were able to observe.
I then show students the range map for the Northern flying squirrel (link provided - University of Michigan site) and the
2 Direct Instruction- Range Maps and Video Observation
Next I explain to students that sometimes completely unrelated species of animals will evolve such that they have very similar physical or behavioral characteristics. This is usually due to the fact that they live in similar environments. I show them the range maps for the Sugar glider and the Northern flying squirrel, as well as a short video on each one. Students take notes about differences between these two species. Note * There are many cute videos of sugar gliders but I selected the one from the American Museum of Natural History because I don't want to promote keeping wild animals as pets.
3 Guided Practice: Finding Other Examples and Taking Meaningful Notes
Next I provide students examples of pairs of animals that are not closely related, and live far apart, yet demonstrate strong similarities.
As a class, we choose one of the examples and briefly research it together, focusing on the following guiding questions:
- What do the two animals have in common?
- Where do the two animals live? geography
- What is the habitat of the two animals? habitat
- What is the scientific name of the two animals? This will show that they are not in the same genus. With older students more detail can be added here..
- How are these two animals different?
Students can take notes with a partner in a collaborative Google Doc, independently in a Google Doc, or on paper. As I teach 3rd grade students, I provide them with an organizer that I share through Google Drive and we work through the questions together.
Here are some examples of animals from different geographic locations that show convergent evolution. Note, there are also examples of animals that live in the same location., such as milk snakes and coral snakes.
- Pronghorn (Antilocapra americana) and Springbok (Antidorcas marsupialis)
- Armadillo and Pangolin
- African yellow-throated longclaw (Macronix croceus) and American meadowlark (Sturnella magna).
- Thorny Devil (Moloch horridus) and Horned Lizard Phrynosoma cornutum
- Emerald Tree Boa (Corallus caninus ) and Green tree python (Chondropython viridis)
4 Independent Practice: Students Research An Example of Convergent Evolution and Create a Mini-Presentation
Students choose their own example of animals that demonstrate convergent evolution from the list provided. They work independently or in partnerships to take notes using the same guidelines as in the guided practice. They then create a short visual presentation to share with the class.
This is a several day lesson.
I ask students to complete short self-assessments/reflection activities at the end of each lesson.
Answer one or more of the following questions in your science journal.
- What is something new you learned today? Does this change your understanding of animals? How?
- What questions do you still have? How do you think you can find the answer(s)?
- What surprised you? Why?
- What will your next step be? Why?