Lesson 22 of 23
Objective: Students will model predation and the effects of changes in the environment on organisms.
Is grass considered “prey”? Why or why not?
This Warm-Up question seeks to address any misconceptions students might have about prey. Expect to hear some students say that grass is prey because it is eaten by herbivores. Provide a clear explanation of why grass is not considered prey. Remind students of the Trophic Level lab. Remind them that the instructions for the grass was that it could not move if approached by the rabbits in the simulation. Explain that it is because grass does not flee or run away, it is not considered “prey”. Predation is truly a hunted and hunter relationship in which you will observe response by the prey to the predator behavior that acts as a stimulus.
Introduce New Material
Begin by showing one or two segments from any number of predator-prey video clips. National Geographic, Planet Earth and Life are all good resources for this type of information. Predator prey clips are intense, uncut examples of the nature of the relationship. This type of content really engages high school students. They enjoy the competition exhibited between organisms and most of them, surprisingly end up cheering for the prey to win the battle for survival. It’s in these moments that I am reminded that my high school students who, though they may look older and at times, act “grown”, they are still capable of being child-like in their awe and interest in science.
Explain that today’s lesson involves modeling predation and the effects of changes in the environment on organisms. Talk about the blue heron and show about 30 seconds of a video clip of the Blue Heron Hunting. It’s good to provide as much information as possible to students in order to establish a common knowledge base that may assist them in the completion of the lab. I learned long ago to make no assumptions when it comes to deciding what students know or don’t know. I find it very helpful for students that I provide as much information as possible to build a quick base of “prior knowledge” connections so that students are set up to succeed. Seeing the bird in its habitat provides them information that they can use in completing the lab. Explain that Blue herons are large birds that live in aquatic habitats and feed on fish, frogs, salamanders, lizards, small snakes, and dragonflies. In today’s lab, students will model a blue heron feeding in a lake filled with fish.
Tell students that the question they will seek to answer is, “How do changes in environmental factors affect the predation yields of the blue heron?” Display the Predation Activity on a LCD projector and verbally summarize the procedure for the class. Remind students that they will need to read the lab in its entirety before beginning. Providing a summary is just a way to give students a broad overview that sets the stage for the lab process. Model how students will “catch fish” using graph paper, rice and toothpicks.
If there are readers in the class who would benefit from reading assistance, scan the lab into Kurzweil (if your district provides this resource) and allow those students to read the lab with computer-generated assistance. Kurzweil is a great classroom tool for readers with below grade level reading proficiency. To get the most benefit from Kurzweil software, you will need to identify and scan the documents in advance of class.
If you do not have access to a computer program like Kuzweil for your lower Lexile readers, then consider pairing them with stronger readers who can assume the role of "reader" in the small group.
Distribute copies of the lab and instruct students to copy the tables onto their own paper before beginning. It might be useful to place hand-outs you plan to resuse in plastic sheet protectors to discourage students from writing on them.
Assign students to work in small groups of two. To expedite the materials collection, send one representative from each group to collect the materials. For example, “Tables B1-B4, go and get your materials.” I label each of the tables in my classroom with a Letter(A-D) and Number(1-8). This organization lends itself to my ability to better manage student movement, even when labs supplies are being distributed and collected. Students will collect a cup of rice, one toothpick and a sheet of graph paper.
The roles of students in each group are that of recorder and predator:
- The recorder will create the data tables, counts the grains of rice received from the predator. The recorder will record the number of pellets caught each round of the experiment on the data table. The recorder will also create the graphic representation of the data.
- The predator will follow the lab procedure of touching rice pellets that are randomly scattered on the graph paper to mimic catching prey. To model the heron hunting for fish, the student will close his/her eyes and lower the end of the toothpick slowly down on to the grid. The predator will remove the grains that are in the square where the toothpick touched and give them to the recorder.
Once all the materials are distributed, set a timer and display it for the duration of the class. Timers help students work efficiently by helping them manage the workload, in light of the amount of time that they have. There are several free timers available. I use online stopwatch,which is a FREE downloadable timer that you can use in the classroom.
Walk around the room to ensure that the lab is being conducted correctly. Walk around the room to ensure that the lab is being conducted correctly. Students should be counting out the pellets of rice and closing their eyes to touch rice grains. The recorder should be carefully counting the grains of rice that are collected and documenting the numbers on the data table.
Students will need some time to conduct the lab as it involves counting rice and selecting rice pellets using the toothpick to represent the heron's beak. The lab requires teamwork between the two members of the group, as one must record the data as the other student collects and counts the rice pellets.
It is likely that students will not complete the analysis questions and graph during class. Before they leave,ask a couple of probing questions that will help them answer the analysis questions independently at home:
- What is the independent variable in this experiment?
- What is the dependent variable?
As evidenced by the artifacts, students were able to accurately reflect the data they collected. They were also able to respond to the analysis with well-written and complete responses that showed that they understood how changes in the environment affects predation.