Warm-Up: A few thousand years ago not all male peacocks had large, bright tails. Explain how variations led to the male peacock we see today with bright, large tails. Is this an example of adjustment or adaptation?
This question allows students to activate prior knowledge about characteristics of living things, as was taught in a previous lesson. Instruct students to engage in table talk for 1-2 minutes before engaging the whole class in discussion. Be prepared to initiate a quick review of the meaning of the terms adjustment, adaptation and variation before students even begin the table talk. Give students an opportunity to lead the review by telling what they know before taking the lead in the review of concepts. Ensuring that everyone is clear about what each term means will lead to more productive thinking and conversation.
Look for students to identify two key points: adjustment reflect response to stimulus that occurs at the organism level while adaptations reflect changes within a species over a long period of time. Listen for students’ ability to explain how the changes in peacock tails occurred. Expect a common misconception to arise, that organisms can just change as they need or want to. Make note of the misconception and be sure to address it later in the lesson.
Inform students of the learning targets:
Introduce the vocabulary associated with the lesson: adaptation, fitness, natural selection, trait, and evolution. Plan to explicitly teach the vocabulary associated with the lesson at the appropriate times within the lesson.
Read each of the following statements aloud:
Explain that each statement will be read a 2nd time. But, this time students should move to the side of the room labeled AGREE or DISAGREE that reflects their opinion. Note: Prior to class, post a sheet of paper labeled AGREE on one side of the room and another labeled DISAGREE on the opposite side of the room.
Instruct students to refrain from talking with one another and to move quickly to the side of the room they choose after the statement is made. This activity serves as a formative assessment of common student misconceptions about evolution. Note the number of students who affirm agreement with these statements.
After completing this activity, instruct students to return to their seats. Do not engage in a discussion about how students responded to the statements as students will have a second opportunity to respond to these same questions at the end of the lesson.
Emphasize that Darwin was not the only evolutionary theorist. Spend time discussing Lamarck’s theory and emphasize how it differs from Darwin’s theory of natural selection. Check for understanding using a visual image the evolution of the giraffe. Instruct students to look at the picture and explain how the giraffe’s neck changed. Listen to their responses as many students will wrongly identify that the giraffe somehow stretched its neck based on need. Swiftly correct this type of thinking and identify it as Lamarckism.
Help students grasp the error of Lamarckism by applying Lamarck’s concept to real-life situations. For example ask, “Can I change my height just because I want to play in the NBA?” or “If I get light brown contact lens, will my children be born with light brown eyes?”
Spend time discussing each of the 5 principles of Natural Selection. Identify each principle and then ask students to think of a good example for each principle before showing an example of each principle. This allows students to practice critical thinking skills and assess their own understanding before answers are provided for them.
Share a brief video clip on the evolution of the peppered moth to help students deepen their understanding of the process of natural selection.
Compare and contrast natural selection with artificial selection using dog breeding as a real-world example since many students will have some experience or knowledge of pure breed and mixed-breed dogs.
Instruct students to consider this question: Are there downsides to artificial selection?
Give students a moment to ponder the thought before instructing them to turn and talk for 1-2 minutes with a classmate. Walk around and listen to their comments to assess whether students are able to convey an understanding that it is not necessarily good if variance is eliminated from a dog breed because not only are favorable traits passed on but also less favorable ones, as well. End the discussion by clarifying that there can be a down side to artificial selection because the process removes variation in a population. Explain that selectively bred organisms can be especially susceptible to diseases or changes in the environment that would not be a problem for a natural selection population of organisms.
Display and distribute copies of Darwin’s Natural Selection worksheet.
Ask a student volunteer to read the first situation. Use an interactive pad to model how to complete each of the five problems. First, explain that students should use the active reading strategy of highlighting key statements in the scenario. Think aloud and identify key statements. Second, think aloud to show students the reasoning(thinking) used to identify which type of worm natural selection has selected against. Emphasize that “fitness” is a measure of how fit an organism is for its particular environment. Third, identify each of the 5 principles of Darwin’s theory of natural selection in the scenario.
Think Aloud script example:
Release students to work in small groups of two on the task. Working in groups of two allows students who are not strong readers to partner with those who are so that the weaker reader will get the assistance needed to process the reading material but still be able to identify the answers to the questions. Also, Kurzweil is an excellent resource for readers who need reading support. This PC-based tool provides reading support or definitions to help students be able to complete work independently.
Walk around the room to monitor students as they work and ensure that all students are actively engaged in the completion of the assignment.
Collect the student work and review the responses to ensure that students were able to correctly identify Darwin's points in the scenarios.
The two student work samples show that students are able to comprehend the text and provide the correct answers to the questions. Student work 1 shows more detailed responses to the questions, while student work 2, though correct for all questions but one has less detailed responses. Also, student work 2 incorrectly credits Darwin with disproving the inheritance of acquired traits. Check students' responses to make sure that this is not a consistent misconception among students. If it is, be sure to clarify that Weisman's experiments with tailess mice disproved the inheritance of acquired traits.
Read each of the following statements aloud and instruct students to move to the side of the room labeled AGREE or DISAGREE that reflects their opinion:
This closing activity serves as a formative assessment to see how well students have comprehended the concepts taught. The expectation is that students will not agree with any of these statements as they are all misconceptions about evolution. If time permits, ask students to elaborate on why each statement is incorrect.