Part 1: Natural Selection and the Peppered Moth (2 days)
Explain to students that natural selection is the way that evolution happens. It is the process in nature by which the organisms that are best adapted to their environment tend to survive and transmit their genetic characteristics to the next generation. Individuals less adapted to their environments are not as likely to survive and reproduce.
Display the Natural Selection Notes (S-8-3-1_Natural Selection Notes.docx). Explain the basic concepts of natural selection. Have students write the vocabulary definitions and basic concepts in their notes. Be sure to explain that genetic variation is important because without it, populations cannot evolve.
Have students read “Natural and Selective Breeding” (S-8-3-1_Peppered Moth Article.docx).
Then, as a whole class activity, create an episodic organizer on the board that sequences the events in the peppered moth story, during the time of the Industrial Revolution. Have students volunteer answers and record those on the board. If students miss important events, prompt them with guiding questions. Refer to the Peppered Moth Episodic Organizer for an example (S-8-3-1_Episodic Organizer.docx).
Then, have students answer the questions on the Peppered Moth Worksheet (S-8-3-1_Peppered Moth Worksheet and KEY.docx). Allow time for them to plan the paragraph for question 6 and write it.
Close the class by having each student write about one other insect with an adaptation that increases its ability to survive in its environment (e.g., wasps are able to sting, so it is more difficult for predators to eat them).
Part 2: Natural Selection Lab Activity (1 day)
To prepare, gather materials for each group. You can save class time by punching holes before class and placing each group’s set of circles in a sealable plastic bag.
Begin the lesson by reviewing the peppered moth story and relating it to natural selection. Ask students, “What adaptation best helped the peppered moths to survive during the Industrial Revolution?” (Dark-colored peppered moths were able to hide against dark tree bark to escape from predators.)
Divide students into small groups and have them clear off their desks. Hand out the worksheet and materials for the Natural Selection Lab Activity (S-8-3-1_Natural Selection Lab Activity and KEY.docx). Read through the procedure aloud with students and answer any questions that arise. Have students do the activity. Circulate around the room and check that students are following the steps of the procedure. Have students clean up and return the lab materials.
Conclude the lesson by asking students to explain their results from the lab activity.
- Students who might be going beyond the standards can create a few more steps in the episodic organizer to continue the story of the peppered moth up to the present day.
- Students who may need opportunities for additional learning can employ reading strategies such as highlighting difficult vocabulary, taking notes in the margins, or partner reading. Also, have students write an outline to prepare for writing the paragraph in Part 1. During Part 2, demonstrate the lab procedure as you read through the steps. It may be helpful to verbally accept students’ responses to the lab questions.
- Students can create a flyer that informs people of the impact that antibiotics have on the offspring of bacteria. The flyer must include:
o Antibiotics kill most bacteria, but some bacteria survive.
o Of those bacteria that survive, their resistant trait is passed on to their offspring.
o A different antibiotic may then have to be used.
Research and provide an example of the resistance of insects to insecticides as a natural selection at work.