Warm-Up: Which do you think will give more genetic variation, natural selection or artificial selection? Explain.
This question allows students to activate prior knowledge about evolution and natural selection taught in the lesson, Mendel's genetics. 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 that natural selection lends itself to greater likelihood of genetic variation while artificial selection does not since breeders only allow animals with the same sets of traits to mate and produce offspring. The traits that are inherited through artificial selection have a greater probability to be the same traits that the parents possess.
The key point to listen for or emphasize is that humans are responsible for the selection of traits in artificial selection, while nature (due to environmental stresses) selects the traits in natural selection.
Inform students of the learning targets:
Introduce the vocabulary associated with the lesson: adaptation, fitness, structural adaptation, behavioral adaptation, physiological adaptation, natural selection, trait, evolution, phototropism, geotropism, and thigmotropism. Plan to explicitly teach the vocabulary associated with the lesson at the appropriate times within the lesson.
Begin instruction by playing a video clip on animal adaptations.
Any number of the animal video clips are typically visually stimulating and engaging for students at any age. Before viewing, explain the purpose of viewing the clip is to give students a greater understanding of the types of adaptations that animals have that allow them to better survive in their vastly different environments.
Distribute guided notes and provide insruction on adaptations.
After discussing each type of animal adaptation, show a video clip that demonstrates the type of adaptation to help students better understand the adaptation in the context of organisms in their unique environments:
Emphasize that not only animals, but plant also possess adaptations that have helped them to survive in different environments. Discuss tropisms and show images to help students distinguish between phototropism, thigmotropism and geotropism. Watch a segment (10 minutes) of a plant life video clip and identify the tropisms displayed in the segment.
Give students an opportunity to discuss the clips and share their reactions to the most types of adaptations displayed in the clips.
As a check for understanding, show a series of images and ask students to identify which type of adaptation is displayed in the image. This activity can be performed whole group.
Explain that writing is a great way for students to demonstrate understanding of concepts. Inform students that they will respond to a 20 Minute Quickwrite prompt during independent practice and then review another student’s work, providing peer commentary on the finished work product.
Explain peer commentary and its purpose. Tell students that all students benefit from peer commentary because it allows students to fixate on their learning and equate what they are reviewing to what they know about the standards and content.
Teach students the TAG strategy for writing peer commentary:
Model how to evaluate and provide peer commentary on writing. Project a writing sample and perform a "think aloud" to show students how to approach evaluating student work. Be sure to provide students insight into the thought process for evaluating a student's writing.
Decide if it will benefit students to share examples and non-examples of peer commentary comments so students will learn what is expected when they perform peer commentary on a classmate’s work:
Display the 20 Minute Quickwrite prompt: How are adaptations related to natural selection? Release students to work independently on the task. Provide sentence starters for students who might benefit from the scaffolding help.
Sentence Starters Example:
Adaptation is __________. Natural selection is_______________. These terms are related because______________________.
Encourage students to utilize their notes to help them organize their response to the writing prompt. Remind students that their responses should include use of the related vocabulary terms. Set a timer and keep it displayed on a projector to help students keep track of the time.
Walk around the room to monitor students as they work and ensure that all students are actively engaged in the completion of the assignment. If students appear to struggle getting started, suggest that they bullet 2-3 points that they know about natural selection and adaptations before putting the ideas together in a response.
Collect the written responses at the end of the assigned time. Hide the students' names and write unique numbers on each student's work, keeping track of which student is assigned to each unique number. Randomly distribute the papers and give students 10-15 minutes to read and provide commentary on other students' work.
Collect the responses with the student commentary and review all comments before returning them to students the next day. It's important to review the comments before returning the papers to the original owners to: 1) ensure that the comments reflect the spirit of the "constructive feedback" that was discussed during Guided Practice and 2) evaluate and/or grade the response from the teacher perspective.
Student work 1 shows a response from student who demonstrates understanding of the concepts and the academic vocabulary. The student's ability to communicate that traits can be favorable or unfavorable based on the environment is a key concept that reflects a depth of understanding. However,while the reviewing student seems to grasp that the writer possesses an understanding of the concepts, the peer commentary is lacking in specific feedback.
Student work 2 also shows a response from a student who demonstrates understanding of the concepts. However, the student does not demonstrate as strong a working knowledge of the vocabulary as the student work 1. The peer commentary does identify that the writer could've better explained the relationship of adaptations and natural selection.
Distribute slips of paper. Display the ticket out the door. Instruct students to describe 4 adaptations that they saw in the video clips and explain how the adaptation benefited the species.
Look for students to be able to explain that the traits they identify are favorable for the environment in which the organism lives. This is a key concept of natural selection and the responses should reflect this understanding.