What is Evolution?
Lesson 3 of 14
Objective: SWBAT construct an explanation based on evidence that describes how genetic variation of traits in a population increase some individual's probability of surviving and reproducing in a specific environment.
I begin this lesson by showing students the following image entitled "The March of Progress" and I ask them to explain if they believe this image is a good image to use when explaining/learning evolution. I have been asked, more than once (sadly), how it was possible that a gorilla ever gave birth to a human. Many students can fully understand the concept of change over time when it comes to other organisms but they have some difficulty relating these same ideas to humans. At this point I accept any and all answers as I am just trying to get students thinking (and to see if they will apply what was learned in the common ancestry unit we just completed).
After students share their thoughts (hopefully some relating to common ancestry!), I show students the following video that gives some background on how this iconic image of evolution of man has become misinterpreted since it was first released back in the 1960s.
After the video I write the phrase "Evolutionarily Successful" on the board and ask students if they caught the host's description of this term. If yes, I have a student state it for the class as I write it on the board. If not (as is mostly the case since kids don't know they should be looking for this), I have the students guess at what it means and then refer to the video to verify (2:49). Students write down this information in their notebooks.
There are two simulations that I have students complete to gather evidence about how variation of traits impacts the survival of an organism. Evolution in Action is a quick and simple interactive that provides good data for students.
I begin by showing students this cK-12 article which is written to support this simulation. The Evolution in Action Student Directions and Questions guides students and gives them some focus questions to answer in their journals. Question 9 ask students why not all of the organisms that "spawn" match the color of the background. The answer is because mutations are random and have no goal. This is important for students to understand as most believe that evolution follows a sort of vision when really it is more like a lucky guess. The following videos depict some students attempting to describe what they are learning from the simulation. The second video demonstrates that while the student has a pretty good understanding on how organisms adapt to match their environment/habitat, he is still unclear on the fact that random mutations are the overall cause of these changes and that sometimes those changes lead to organisms being able to live longer or shorter lives. (This idea is further developed in the next lesson).
Natural Selection, Evolution and Mutation is a PhET Lab simulation that I have the students work through on day two. This sim has variables that students manipulate to see the impact on the population. To allow students to practice planning and carrying out investigations (SP3), I give them guidelines rather than specific directions. The following video explains in more detail these guidelines.
To end the lesson I go through Recipe For Evolution: Variation, Selection & Time which is a resource from Learn. Genetics Genetic Science Learning Center which is a wonderful resource on a large variety of biology topics. This reinforces some of the things the students should have learned by doing the simulations.
To assess student learning, I have students write a response to the following prompt in their journal: explain how genetic variation of traits in a population increase some individual's probability of surviving and reproducing in a specific environment. Use evidence from your investigations to support your answer. As this is a formative assessment I just use a 3 point scale to assess this journal entry:
3 - Demonstrates strong understanding of the concept.
2 - Demonstrates good understanding of the concept with only minor misunderstandings
1 - Demonstrates poor understanding of the concept with major misunderstandings
I make sure to meet with students who scored a 1 to ensure that their misunderstandings are cleared up before moving on to the next lesson.