Getting Food to The Cells (2)
Lesson 2 of 7
Objective: Students will be able to make connections between the digestive, circulatory and respiratory systems in understanding how food and oxygen gets to the cells.
The purpose of this lesson is to make the connections between the circulatory system and the digestive and respiratory systems. This is done in two ways. First, students will be adding the connections into their notes from the day before and second, students will be completing the narrative, to show how food crosses from the blood into the cell.
Learning Goal: Understand the connections between the circulatory system and the digestive and respiratory systems.
Opening Question: How do food and oxygen get to the cells?
As students are coming in, I am standing at the door reminding them to "Get ready" (Get their folders out of the bins) "Get set" (Get in their seats with a pencil) and "Get Engaged" (Get started on the learning goal.
After students have recorded their responses on their learning goal sheets, I randomly call on students to share their answer with the class.
For the hook today, I ask students to share out their responses to the opening question. Then I say, "Open your notes from yesterday and try to mark where the food and oxygen enters the bloodstream. Check with your partner to see if you got it. Use the book* if necessary."
As the students are doing this I walk around and listen to what they are saying. At the end I go to the board and mark on my notes the villi and air sacs. Then I ask the students to discuss what the villi and air sacs have in common structurally that allows food and oxygen to cross a membrane into the blood.
Students have a short period of time to try to find this answer in the readings and then we have a very short discussion on the fact that the membrane in both places must be thin enough for the molecules to pass into the blood.
*Yesterday, students used our science text book to read about ..... Similar readings can be found online, on sites such as cK-12.
It's important not to make assumptions. Instead, make clarity by being specific. So, the purpose of this section is simply to remind students we took notes yesterday and for me to check how far the students have gone. Generally, my classes needed a few moments to finish up.
I ask the students to hold up fingers to show me the amount of time they need to do this and choose a reasonable amount of time. I also use this time to show students once again what my notes look like, asking them to make sure they are finding and recording the "correct" information.
Yesterday, students worked collaboratively on these notes. Now that students have all had support in making the notes, today we are working independently because it tends to be faster and more on track. I put a timer on the projector and let the students know how much time they are going to have. You can find an online timer here.
Today, I want students to add onto their notes by drawing in the connections with the circulatory system. If you have some red pens to loan out it makes a nice splash on the page to put the connections in red and really helps the students connect the ideas. This is what mine looked like.
The purpose of this section is to finish the lab from yesterday and to make connections with our notes from today. I start this by reminding students that particles have to be able to cross a membrane at different times; sometimes to get into the blood and sometimes to get into a cell. We go back to yesterday's lab and I ask students to predict whether size makes a difference so that substances can cross the membrane.
While they are discussing, I get my supplies set up. You need Iodine, Benedict's solution, test tubes and a microwave.
First, I tell students we are going to test the water in the beaker for starch and sugar. We already know that there is starch and sugar in the beaker, but this will show us what a positive test looks like. I fill two test tubes with water from the beaker. In one, I put a few milliliters of Iodine (which is brown). This is the test for starch. The liquid will turn black.
In the other, I put a few ml of Benedict's solution (which is blue) and then put the test tube in the microwave for 15-30 sec. This is the test for sugar. The liquid will turn bright orange.
Now, we are ready to test the water in the bag. If the lab has been done correctly there will be sugar but NO starch in the bag. I cut off one of the rubber bands carefully and empty the bag into two test tubes. We repeat the tests for starch and sugar and then record the results.
The purpose of this section of the lesson is to solidify the lab thinking with students so that they understand what has happened. I find that since this is the first time we have used chemicals and analyzed results, some students are able to immediately connect with the overall purpose and others will be stuck on the fact that there was a color change.
It is absolutely necessary to go back to the purpose and remind the students of what we were trying to show. I review the entire lab so that students can grasp the connections. My expectation of students is that they are listening and participating. I often use a form of question and answer to make sure that students are accountable to focusing on learning. A screencast of what that looks like is below.
Closing Statement: Our learning goal today was to understand the connections between the circulatory system and the digestive and respiratory systems. We did this by recording in our notes where the connections were physically and looking at how the size of the particles determined what molecules could pass through the membranes and what molecules could not.
Closing Question: What sort of digestive problems might occur if the vili in the small intestine did not take in the nutrients? What might the result be of the person?
Read more about effective ways to close your lesson, no matter how much time you have left!