What Did T-Rex Taste Like?
Lesson 3 of 12
Objective: SWBAT use a cladogram to make hypotheses and explain that all living creatures are related by common ancestry.
This lesson is based off What did T.rex taste like? from the University of California, Berkley.
It is important to activate student thinking prior to starting this activity. The purpose of this portion of the lesson is to get students thinking about how many traits even the most dissimilar animals have in common.
This can take as little as 5 minutes or as long as a class period, it depends on what you want your students to get out of this activity. Students are assigned a pair of organisms, such as dolphins and seals or lizards and chickens, and they are tasked to list as many features as they can think of that their two organisms have in common.
I created the Compare and Contrast Organisms Chart that states the organism pair and provides a picture of each animal. I cut this chart into strips and assign students to partners. Each partner group picks one of the strips at random. Because I believe it benefits students to have enough time to take thinking deeper and find commonalities beyond the obvious, I allow students some time to use the internet to find the common traits that may not be obvious from outer physical features or environment that are found in the pictures provided on the strips. The Student Work Sample: Comparison Charts shows some of the answers students developed.
When students have compiled their list (on chart paper or a shared Google Doc), have them answer the following questions:
- Do your organisms share features because they were inherited from the same ancestor, or did your organisms evolve (develop over time) similar features independently? Explain your thinking.
- Do you think your organisms are closely related to each other? Why or why not?
To clarify what the first question is really asking, I use the following example to explain:
Birds have evolved the ability to fly. Bats, which are mammals, also have the ability to fly. Do they each share the ability to fly because they had a common ancestor that passed along that ability or did they each get the ability to fly on their own in response to their environment?
(Students typically say they developed flying independently as one is a bird with feathered wings and one is a mammal with "leathery" wings.) Once students understand what the questions are asking, they work in small groups to develop a group answer. This video gives a sample of answers from my classes.
I ask the class to consider all of the lists shared and determine if there are any traits that all of the organisms have in common. Depending on the lists created, you might have to break this portion into animals/plants and then compare all organisms. Either way, the goal is for students to recognize that all organisms share common traits.
Now that students have developed an idea that life seems to be connected through common ancestry, students are ready to gain a deeper understanding of what this actually means and how scientists illustrate the ancestry of organisms.
This portion of the activity has students work through the module What did T. rex taste like? I prefer to have students work with a partner so they can process the new information together. I ask students to document new vocabulary and any questions or concepts they don't understand in their science journals. This terms list can be given to students with IEP or 504 plans to ensure they have all necessary terms.
This module is divided into 5 folders. Each section has checks for understanding built into it so I do not feel it is necessary for students to take notes as they complete the module. You may want to require students to document questions they got wrong so you can discuss these with the class.
Below is a brief description of the content in the separate folders but it is extremely beneficial to work through the student modules prior to teaching this lesson.
Folder 1 uses family trees to explain how traits are passed though generations and introduces the idea of a common ancestor.
Folder 2 demonstrates how to read a cladogram to determine the relatedness of organisms.
Folder 3 goes into more detail on reading and using cladograms to determine evolutionary relationships and has more questions to students to practice answering.
Folder 4 discusses how studying evolutionary relationships helps to develop and test hypotheses regarding life's history. This folder shows how to turn a cladogram into a chart. Students can use this data table or create a similar one in their science journal.
Folder 5 introduces students to the closing "special assignment" that requires students apply what they learned throughout the module.
While students can likely complete the first 4 folders in one sitting, I recommend having students work through folders 1-3 in this sitting and folders 4-5 together (the special assignment in the next part of the lesson). This allows students some time to process and "digest" the necessary background information without being overwhelmed with information at one time. Folder 4 is a bit more challenging and is the information that is most relevant to complete the folder 5 activity.
Students begin by completing folder 4 and completing the data table. Students will need this completed data table to complete the special assignment (assessment) in folder 5. Students will also need this cladogram and additional data.
Students will examine the questions below. For at least two of the questions:
- Decide if it is possible to answer the question with the data provided (the cladogram and data tables).
- If it is not possible, what information is needed to be able to answer the question?
- If it is possible, what kind of hypothesis would you make? What is the evidence for your statement? In your justification, make sure that you include information about common ancestors and shared inherited features. What other evidence would you look for that would support or refute your hypothesis?
BONUS: What other kinds of questions might be answered using the cladogram and data tables?
- Did T. rex have an amniotic egg?
- Was T. rex warm-blooded or cold-blooded?
- Could T. rex have had feathers?
- Did T. rex have color vision?
- How many chambers were there in T. rex's heart?
- Did T.rex sing to its offspring?
Folder 5 introduces students to this assignment and ends pretty abruptly. I answer specific questions for them but I do not tell them how to accomplish this task. I have found over the years that there are many different paths to success and students need to practice solving this type of problem on their own. Students can be confused by this part of the simulation (I honestly don't know why, the directions are right there!) and they are likely to need some clarification. I had the students open a Google doc and do the following:
- Type the question they are addressing
- Infer the answer to that question (based on the cladogram and data provided)
- State WHY they are making that inference (support w/evidence from cladogram and data)
- List one or two other pieces of information that, if they knew those answers, might help them be more sure of their inference made in step 2 (not going to lie, this one was challenging for most students)
At the completion of this activity you might want to have your students take this post-test. Here is the key. I like to use this post-test as it is short and takes little time but really shows what students have learned during the module.