In this two-part lesson, students learn about both allopatric and sympatric speciation. First, students study allopatric speciation by visiting the Web feature Allopatric Speciation. Students watch as, over time, the fictional pollenpeepers evolve into divergent species after being blown to separate islands. In the second part of the lesson, students learn about sympatric speciation by studying hummingbirds and lacewing flies. They watch a video about hummingbirds, which have developed into new species to adapt to different ecological niches, and listen to the songs of lacewing flies, which have evolved into different species due to song preference.
Allopatric speciation occurs after a population becomes separated geographically by a natural barrier. Sympatric speciation occurs without a geographical separation.
- Learn how new species evolve
- Understand the difference between allopatric and sympatric speciation
- One to two class periods
- An Origin of Species Flash Interactive
- Hummingbird Species in the Transitional Zones QuickTime Video
- Allopatric Speciation JPEG Image
- Isolating Mechanisms: Lacewing Songs Flash Interactive
- Convergence: Marsupials and Placentals PDF Document
Part I: Adaptive Radiation
1. Have your students view the Allopatric Speciation graphic. Discuss speciation, especially allopatric speciation, with your class.
2. Assign students the numbers 1, 2, 3, or 4 by having them count off.
3. Have students go to the Web activity An Origin of Species. The ones cover the mainland, the twos cover Windsor Island, the threes study Norcross Island, and the fours examine Warwick Archipelago. Students can work in groups, depending on the resources in the classroom. Have students try out the activity and view the Species Gallery. Ask them to take notes on what happens to their species over time.
4. Once students have had a chance to view the Web feature, discuss the following questions:
- Over how long a time period do the pollenpeepers evolve in this Web feature?
- What influence do competition, habitat, food, and predators have on evolution?
- What is a biological species?
- How can one species, such as the hypothetical pollenpeeper, adaptively radiate into different species?
- What conditions contribute to speciation in a localized area?
- How might a species become reproductively isolated (unable to reproduce fertile offspring)?
Part II: Speciation Without Geographic Isolation
5. Have students watch the Hummingbird Species in the Transitional Zones video and read the attached backgrounder.
6. Then have students listen to the lacewing mating calls on the Isolating Mechanisms: Lacewing Songs Web activity.
7. Discuss the following questions as a class:
- Why did the hummingbirds in the Andes evolve into new species?
- What feature of the birds does Chris Schneider compare?
- How did scientists used to think new species were formed? How does Schneider's research modify old ideas?
- Why do the lacewing flies evolve into new species?
- Could human beings ever evolve into divergent species? Why or why not?
- How are the factors that influence hummingbird evolution similar to those that influence the evolution of the fictional pollenpeepers? How are they different?
Optional Lesson: Convergence
8. The idea of convergence plays further havoc with our desire to place all living things on an orderly evolutionary tree. For example, marsupial mammals in Australia and placental mammals in North America look to be closely related, but in fact they share a common ancestor way, way back. They have evolved similar features due to their similar habitats. Students may find this resource intriguing. Go to Convergence: Marsupials and Placentals.