Biomagnification and relationships in ecosystems
In this lab, which will take a double period, the students will be able to visualize the effects of biomagnification. Biomagnification is when a toxin accumulates in the food chain, with the most found in our tertiary consumers. The students will already have gone through a lesson about the overall causes of loss to biodiversity, and pesticide/ toxin is one of those causes. As an introduction to the lab, students will also have already gone through a smaller powerpoint discussing the main points to biomagnification. This is a hands-on activity to display the passing of toxins in the food chain because students have trouble understanding how a toxin could only be dangerous to specific levels of species on the energy pyramid. As before, my goal for this lesson is to lecture less and get the students involved more. I hope to do this by making up for the longer lecture with a longer hands-on lab.
HS-LS2-2: Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and population in ecosystems of different scales.
TIMELINE OF ACTIVITY:
The lesson will start with me reminding the students what DDT is (a harmful pesticide) and what biomagnification means (DDT accumulating as you go further up the food chain).
2 old videos (https://www.youtube.com/watch?v=-UiCSvQvVys and https://www.youtube.com/watch?v=UBqksDzsOpI&list=PLhmvvnHzNcXx2CuCsI1CAYrpazSDwNaba&index=7 ) associated with DDT propaganda will be shown.
I will then poll the students for thoughts from the video. I would mention specific things about the video like how mosquitos grow in water and that is why they sprayed the water. Now, I can use this as an intro to why we use algae in the lab. I can then talk about the West Nile virus and how DDT was used to kill the mosquitos around Long Island.
Now, the lab begins. A packet will be distributed to the students and I will demo the lab before I give them the materials to start. I want their full attention because the procedure in the packet can get kind of confusing. The students will be using the candy corn and marshmallows to demonstrate mathematically how toxins (marshmallows) build up as you get higher in the food chain. Math modeling is shown by counting the number of marshmallows after each “feeding” and determining the average of DDT per organism. After the 3 trials are completed, students will take the average of each trial per organism for an average amount of DDT per organism.
Students will complete the table that tracks how much DDT is in the system of the algae, minnow, sunfish, and osprey. After the table is complete, there are 7 analysis questions for students to answer.
Shown below is the packet the students were given.
When the students are done filling out the packet, we will go over the answers as a class.
To close out the lesson, we will have a discussion about another fertilizer and its effects. This video will be shown: https://www.youtube.com/watch?v=5xJKA1PdR9U
Students will be asked: Is this a fact? Is this an advertisement? How convincing is it? Are they biased? What are they selling? Students will then be asked to talk about/ debate our essential question. Some probing questions can include (if conversation is hard to start):
What are pros and cons to each pesticide?
Did you hear anything in this recent video that was alarming to you?
Fertilizer vs organic?
Do you think DDT should have been banned in the first place?
REFLECTION:
When I carried out this specific activity with my students, they really enjoyed it. It was able to give students a visual of biomagnification and allowed them to apply this to the world. The point of the activity was to show that the osprey would have the most DDT in its system, changing its body chemistry so that their egg shells are thin. Because of DDT, the baby birds would get crushed by their mothers accidentally. The students went through almost a full day of lecture the day before this double period lab, so it was a good break up. Not only did it supplement the lesson, it allowed students to be hands on with their learning. I believe I reached my goal with this lesson because of the balance I achieved. Not every lesson will allow for hands-on-ness, but if you can make it up in other ways, the students will still get out of it what you want.
Hi Julia! Thanks for the really great lab activity! I really love this visualization that students will have with this one. Labs are such a great time for all the things that students are learning to come together. A goal of mine is to lecture less as well. It is harder in the beginning of lessons since there is background information you want to make sure students have. I like what you mentioned at the end of your post, though. How you can make up for the classes that might have a longer lecture by doing full day activities. I also really like how they mathematical modeling will be taken into account with this lab. Finally, I appreciated the timeline you gave us. As I do my lessons I am trying to figure out a way to have some notes by my side to pace myself. I think this is something I will try as well.
ReplyDeleteHi Julia! I really like this lab activity! Integrating real-world substances such as candy-corn and marshmallows is a great way to interest the students on the topic of biomagnification. I believe that students learn best by doing so having this lab activity integrated into the lesson is a great way to get the students interacting with the science with their peers, and seeing that science is fun! In my blog posts I also work to try to create hands-on activities for my students since I've learned that they learn best by doing. One question I have is: How long is a typical class period for you? My chemistry classes are 45 minutes each so if I were to include a short lecture prior to the lab activity it may take longer than one class period.
ReplyDeleteOverall, great job!