The Why Behind Teaching This:
Unit 3 addresses standards related to the transfer of energy and matter between organisms in an ecosystem. The unit begins with identifying what solar energy is and what two forms of energy solar energy provides life on Earth. This is an important foundation for understanding standard 5-PS3-1: Use models to describe that energy in animals' food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun. We build on this knowledge throughout the unit in other lessons related to photosynthesis and how animals use the energy they get from food. In this unit students will also be conducting experiments to gather evidence to support their belief that plants get the materials they need for growth from either water, air, or the soil. This is covered in standard 5-LS1-1: Support an argument that plants get the materials they need for growth chiefly from air and water. Students will also be creating food chains and food webs to describe the movement of matter among organisms in an ecosystem. This is covered in standard 5-LS2-1: Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.
I combined these three standards all into unit 3 because teaching them together allows students to see how they are all connected. The energy that plants get from the sun is stored in their parts until animals consume them. Plants cannot absorb this energy and reproduce without other materials from the environment such as carbon dioxide from the air, and water and nutrients from the soil. The animals that consume the plants, use part of the energy for growth, reproduction, etc. but they also store some of the energy. That energy is then passed on to other animals when they are eaten by other animals. All of the energy that is available in an ecosystem can ultimately be traced back to the sun. Teaching all of these standards together, instead of in isolation of each other, makes that connection easier to see.
This specific lesson addresses standard 5-PS3-1: Use models to describe that energy in animals' food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun. Students will be tracing the flow of energy through food chains from the sun to other organisms in an ecosystem. It also addresses standard 5-LS2-1: Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment. The last organism in a food chain is a decomposer which recycles matter from dead organisms back into the soil for plants to use for growth and reproduction.
The goal of today's lesson is for students to model the flow of energy from the sun, through organisms in an ecosystem using a food chain.
Students will demonstrate success on this lesson by creating a food chain that accurately demonstrates the flow of energy through an ecosystem.
Preparing for Lesson:
Introducing Food Chains
I pass out a whiteboard and marker to each group in the class. I begin the lesson by showing information about food chains on Kid's Corner website. I select one student from each group to be the reader for their group. I ask them to read the three short paragraphs on the first page to their group. I provide a paper copy of the Food Chain Website Reading Passage if needed. The students I select as the readers, read clearly and loudly so I know all group members will be able to hear and understand them. By having one reader, it ensures all group members get through the information at the same time and are ready to discuss together. After reading, I tell groups to discuss the information, and decide on three key details related to food chains. I give groups about 5 minutes to discuss while I circulate to listen to conversations.
Seeing the differences between the details pulled out of the text was interesting. Considering it was only three short paragraphs of information, I figured there would be more similarities. Some groups put very general information on their board, like animals get energy from the food they eat. I wanted to see all groups put that some animals get energy from plants and others get energy from other animals. Also, not all groups included the overall purpose of food chains as a way to show how energy flows through an ecosystem. This is also something I would have liked to see on every groups board.
I continue on by clicking the link at the bottom of the page that says "Click to learn about bigger food chains". The only thing I discuss on this page are the three pictures of food chains. I begin by showing just the first two, and not scrolling down to reveal the last one. I ask several questions to check for understanding and to make connections to content previously learned.
At this point, I scroll down to reveal the third food chain. This food chain shows that the energy from the sun goes to the grass, then to the grasshopper, mouse, snake, hawk, and finally to the mushrooms (fungi) when the hawk is dead. We briefly discuss this food chain and describe how nutrients are "recycled" in the ecosystem.
Diagramming in our Notebooks:
We add some information in our science notebooks for students to refer back to for homework, quizzes, assessment, and throughout the year to prepare for the end of the year assessment. I place my notebook on the overhead to model for students while they have their notebooks open at their seats. By me recording information in my notebook as we discuss it, I am providing a visual for the ESE and ELL students, as well as those who struggle with writing and spelling.
As we add information into our notebooks, I am spending time explaining each part of the food chain and giving examples. This is when the content of the lesson is taught.
Click for a more up close view of the picture of notebook page
Practicing Food Chains With a Game
I continue using the food chains website by clicking on the link on the left side of the page that says "Food Chain Games". There are 5 games, beginning with a simple food chain that only contains 3 organisms, to more difficult food chains that include decomposers. Students work together in groups to create the food chain on their whiteboard before I drag the items to the boxes to see if they are correct. I award points for groups that get them correct and award the winning group with tickets (used as the class incentive). Each game lists the words for the items as well as the pictures. It takes too long for students to try and draw the pictures so I ask that they just write the words for their food chain.
Game one: Simple Food Chain
All groups put the organisms in the correct order in their food chain but one group puts lines between them instead of arrows, and two groups did not put anything between them. These three groups do not get points and I stress the importance of arrows so we know the direction energy is going.
Game two: Bigger Chain
All groups draw out their food chain accurately for this. The all included arrows going in the correct direction with the organisms in the correct order. I think a couple of groups missing the first one was a good thing because it allowed for a review of the importance of the arrows.
Game three - six:
Groups were able to correctly organize all food chains for the various ecosystems including the one with a decomposer. They enjoyed the animation of the animals eating the other things which I was worried may be too young for them but they were actually begging me to let it play through before going on to the next one.
Next is the "I've reviewed, let's keep going" link. If teams are tied I go on to these games as the tiebreaker, otherwise I skip them.
Building Models of Food Chains
Now that students have read about food chains, discussed important components of food chains, diagrammed food chains in their notebooks, and practiced building food chains in the game, it is time for them to independently create a food chain. I provide each group with food chain cards and food chain arrows that have been copied, cut, laminated, and hole punched with two holes at the top. I also provide each group with two pieces of yarn about 5 feet long.
Groups lay out the cards to create 2 food chains of their choice. Numerous different food chains can be created using the cards provided. The only criteria I give them, is that each food chain must contain at least 3 organisms but I encourage them to come up with something that contains more. I do not provide them with any other information such as one of those items must be a producer, or that their food chain may or may not include a decomposer and the sun (some food chains do, while others do not and I only provided them with one of each so both chains will not contain them). After they have 2 planned out, they run the string through the holes at the top of the cards so that they create a hanging food chain. They must place an arrow between each organism card in the food chain or it will not be correct.
I leave them to work while I circulate to make sure all students are working and on task. As I circulate I ask each group to explain their food chains to me. I ask each group to explain the role of the sun in their food chain. I also ask how the carnivore in their food chains are using energy from the sun to move and grow.
Some groups were disagreeing about where certain animals would fit in the food chain. As you can see in the Building Food Chains Video 1, the two girls cannot agree on whether a pelican would eat a shark or a shark eat a pelican. As I circulate to listen to conversations, I have to remind several groups they do not have to use all of the animals. The group in the video ended up not using the pelican in their food chain.
In the Building Food Chains Video 2, the group is assembling their food chain. You can see that it is easiest when one person is holding one end and putting the cards in place as another person slides them on.
Sharing our Food Chains
As each group finishes their food chains, they carry them up to me and I tape them to the front board. I do not comment on any errors that are made, I want to see if students can pick out the errors as I go over them.
After food chains are hanging up for all groups, we discuss similarities and differences. We begin with what they have in common (arrows all facing the same way, all include a producer at the beginning, etc). Then we discuss differences such as some groups having the energy from the grass going to a grasshopper and some going had it going to the rabbit. Some groups also included the sun in some and the decomposer in some, but not all groups chose to use these. As we discuss this, I point to each of the food chains without the sub and ask where the plant got its energy and the students tell me the sun. Just because it isn't there, doesn't mean it is any different then the other plants. I also ask students if there are any food chains that they think are not set up correctly. There were several that had the the bacteria at the beginning of the food web as the producer instead of at the end as the decomposer. There were also several that has the rabbit consumer an animal. I addressed both of these by reviewing what decomposers are and having the students give me examples, and by identifying a rabbit as a herbivore. The students knew the rabbit was a herbivore when I asked so I think it was an error made when trying to use as many organisms as possible.
I select two food chains that were assembled correctly, with no errors, and have students make some inferences. I ask them to discuss with their group what would happen to the organisms in the first food chain if there was a drought and the producer died out. After a short discussion, I have a couple of groups share and they both say the organisms would all die as well. I have them explain why so I am clear they can support their reasoning. I then ask what would happen to the organisms in the second food chain if the top consumer (carnivore) dies out. I give groups a minute to discuss this, then choose 2 group to share. One group said the populations of the other organisms would increase. The other group said that the population of the herbivore would increase because the carnivore is not eating it. As the population of the herbivore increases the population of the producer would decrease because there are more herbiivores now eating them. I went back to the first group and asked them if they agree with group two, or if they sill think both would increase. They agree with group 2 after hearing their explanation.