Adaptation, Selection and Evolution: How environments shape species
Lesson 7 of 8
This lesson covers the different ways species can be shaped by the environment, including both natural and artificial selection, as well as a discussion of how biotic and abiotic factors in the context of a specific ecosystem determine what "adaptive" means.
The lesson essentially consists of two parts:
1. A pre-class textbook reading and homework assignment focused on close reading techniques, critical-thinking questions, and content vocabulary development.
2. An in class presentation that provides supplementary examples to review the concepts and vocabulary from the chapter along with a class discussion seeking to draw students into more critical examination of the topic at hand and assist in their ability to connect the concepts to their personal experiences.
The textbook reading comes from Environmental Science: Your World, Your Turn by Jay Withgott.
If you do not have that particular textbook, I would recommend finding a similar chapter or chapters and modifying the lesson accordingly. The concepts covered in this chapter that I would look for in a different text are...
- Natural selection (overproduction, variation, selection, and adaptation)
- The species concept and speciation (with a special focus on how allopatric speciation results from geographic isolation and can be a direct result of environmental and geological factors acting over a long time)
- Mutations (both as a natural process and because of exposure to mutagens)
- Artificial selection (selective breeding)
- Evolutionary fitness (especially in the context of adaptation to environmental conditions)
- Extinction (even better if your text mentions mass extinctions and extinctions due to human activity)
Alternately, the powerpoint attached to the Direct Instruction section covers most of the same concepts and vocabulary as the chapter. If you have a shorter class period, you may want to skip the reading assignment and assign the discussion questions as homework. You could then hold the class discussion on the following day.
In my case, I assign the textbook reading on the meeting previous to this lesson. In that way, students will have already covered the concepts on their own and the powerpoint presentation will be less of a lecture and more of an opportunity for students to ask questions and clarify their understanding.
Connection to Standard:
In this lesson, students will prepare for class by reading and determining the central idea of a text, establish familiarity with relevant scientific vocabulary, and then draw evidence from the text to support arguments and opinions presented as part of their participation in a group discussion.
Like I mentioned above, I assign the textbook reading as a homework assignment to be completed upon arrival to this class period. The powerpoint presentation is then more of a review and an opportunity for students to ask questions.
Wondering why I choose lecture as a pedagogical strategy? Read this rationale.
When class begins, I ask students to get their homework out and first give them about 10 minutes to discuss the critical thinking questions with their group members. During this time, I walk around and put a stamp on completed homework and answer any questions that students bring up. If students bring up a good question or insightful comment, I ask them to please remember to bring that up in the larger class discussion to follow the presentation.
Affording this time before the presentation allows students to "field test" their answers with a smaller group, increasing their confidence to participate in the larger discussion. Also, because the group shares the same grade for participation in the discussion, it allows the ideas of individual members to influence the thinking of their peers which may lead to greater insights or even new questions. Finally, while I walk around, I listen to the nature of student discussions and get a better sense of what kinds of questions may be floating around the room, allowing me to emphasize certain aspects of the lesson or offer more detailed examples to scaffold the instruction.
After I have stamped all the homework assignments, I distribute the note sheet that accompanies the presentation. As I've mentioned in previous lessons, offering students a note sheet provides a readymade study guide for later and allows students to focus on their thoughts and the concepts being discussed as opposed to focusing all of their attention on copying down copious amounts of notes.
Following the presentation, I let students know that we will wrap up by having a class discussion to review the concepts of the lesson. Again, depending on your class length, it may be preferable to have this follow-up discussion on the following day.
The discussion protocol for this lesson:
all groups are required to participate in the discussion and will receive a “participation” grade for the day
groups with more than one member that participate will receive a higher participation grade
groups that participate more frequently will receive a higher grade
These criteria make the group collectively responsible for their grade and accountable to each other. If no one in the group participates, the group as a whole will receive a failing grade. If only one member of the group participates, regardless of how often, the group can’t receive any grade higher than a C.
To keep track of participation, I begin by making a map of the class with the group tables labeled by group name. Since there are four students at each table, as a student from a particular group participates, I make a tally mark in the position of that student in their group. In this way, I can tally how often the group participates, which members are participating, and how often. To determine "average" participation, I add up all tally marks and divide by the number of groups, rounding down. I then use this rubric to determine their participation grades.
See this discussion guide for a more detailed explanation of how to lead this particular discussion.