Photosynthesis

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Objective

SWBAT identify the three things needed by plants for photosynthesis and the two things produced from photosynthesis.

Big Idea

Students diagram photosynthesis and make bracelets to help them remember the process.

Rationale and Preparation

The Why Behind Teaching This: 

Unit 3 addressed 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 provides background knowledge needed to understand 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.  In order for students to understand how energy from the sun is stored in plants and then transferred to animals for body repair, growth, motion, and to maintain body warmth, they must understand the process of photosynthesis.  They must understand how the energy from the sun is converted to sugar and stored as chemical energy in the plants.  

Lesson Goal: 

The goal of this lesson is for students to understand the types of matter and energy that enter a plant for photosynthesis to occur and that after these items combine, chemical energy and new matter are created.  

Success Criteria:

 Students will demonstrate mastery of the lesson goal by completing a photosynthesis miniquiz at the end of the lesson.  

Preparing for Lesson:

Warm Up:

  • Teacher will need the computer and overhead to show the photosynthesis rap song
  • Each group will need a whiteboard and marker.   

Guided Practice: 

  •  Teacher will need a visual model of the parts of a plant (can use the models created in the plant part lesson from this unit) to use while tracing the flow of water, light, and carbon dioxide to the leaves for photosynthesis to occur. 

Explore: 

Prepare a ziplock bag for each group that contains the following (if you have 4 students in each group):

  • 4 pieces of string, each cut about 8 inches long 
  • 4 green beads
  • 4 blue beads
  • 4 black beads
  • 4 yellow beads
  • 4 UV color changing beads (I order these from the Steve Spangler Website)
  • 4 pink beads
  • 4 white beads

You will also need a copy of the photosynthesis bracelet sheet to project on the overhead for students to see. 

Each student will also need their science notebooks for diagramming

Wrap Up: 

A copy of the photosynthesis miniquiz for each student 

Warm Up

10 minutes

Photosynthesis Rap: 

I use music to introduce the process of photosynthesis to the class.   I chose to use this rap because the lyrics touch on the fact that solar energy is converted to chemical energy, two things we have discussed in the past and will be reviewing today.  Many of the songs I listened to left out this important detail.

I show the video and listen to the rap with the class.  

                            

After playing the whole song one time, I provide each group with a white board and marker and ask them to divide the board in half.  I instruct them to title one side Need and the other side Produce. I tell the groups they cannot talk to each other, I want them listening to the lyrics.  Each person in the group will get the board to record one thing they hear on the side of the board it belongs.  I replay the first minute of the song again.  This part tells everything we are going to discuss today:

"...Sunlight and transfer of energy lets get into this process of chemical reaction. Plants take water, sun and CO2 to make glucose the sugar they make for food.  They also put oxygen into the air..."

I have the student in the group with the board pass it on to the next person.  I replay the first minute again and then have them pass the board.  I play the first minute 2 more times so that all group members have a chance to record something on the board.

We share what groups have recorded on the boards.

Guided Practice

10 minutes

Reviewing Plant Parts and Connecting to Photosynthesis: 

I begin to make the connection between what we have already learned about plants, to the process of photosynthesis by getting out one of the models created by a group in our plant parts lesson.  The model has the roots, stem, and leaves labeled but the role of what each part does is hidden inside the folded label.  I point out some of the words that all of the groups had recorded on their whiteboards from the rap: water, sunlight, CO2.  I ask students how the plant gets water and the tell me through the roots.  I ask them to explain what happens to the water once it is absorbed by the roots.  This is all review from the previous lesson. I then ask how the plant gets sunlight and they tell me it is absorbed into the leaves.  I ask if anyone heard the word in the rap that is the part of the leaf that absorbs the light.  No one can tell me so I write the word "Chloroplast" on the board.  I then ask what CO2 is and how it gets to the plant.  Students tell me it is Carbon Dioxide and it is absorbed into the leaves.  I ask them what else they can tell me about Carbon Dioxide.  The first thing they tell me is that it is a gas and when frozen it is dry ice (this is something we discussed when we did an activity with dry ice).  Another student tells me that carbon dioxide is what we breath out.  

As we are discussing each of the items above, I am using the model to point out what is happening and try to stress that everything combines in the leaf without coming out and saying it.  I ask them what part of the plant photosynthesis occurs in and they are able to tell me the leaves. I review what we just discussed by saying "so water is absorbed through the roots and goes through the stem to the leaves and light and CO2 are absorbed through the leaves.  What happens once it is all in leaves?"  I ask them to turn and talk with their group about this, and to come up with an idea of what they think happens.  I circulate to listen to conversations and ask questions to get them thinking more about this.  

I am listening for a group to discuss that the light energy changes the particles in the water and CO2,  and create something new, oxygen and glucose (sugar).  I hear groups discussing that the items mix together and become something new but none of the groups are discussing how the particles are combined to create something new.  Earlier in the year we discussed how chemical reactions can break the bonds of substances and recombine them to create something new.  This is something I notice I need to review.  

After a couple of groups share what they discussed, I write the words water and carbon dioxide on the board.  I ask them to tell me what water is made up of and they tell me H2O which I record on the board next to the word water.  I ask what the H stands for, hydrogen, and what the O stands for, oxygen.  I then ask them what carbon dioxide is made up of and they tell me CO2 which I record on the board next to the words carbon dioxide.  I circle that information and draw an arrow coming off of it.   As I circle them, I say "once all of these items are mixed together, we get glucose or sugar, and oxygen". I write the words Glucose and Oxygen on the board after the arrow.  I record C6H12O6 under the glucose and O under the oxygen.  I ask them what they notice about the formulas.  They tell me that all of the same letters are used.  I point out that the same atoms make up what is used for photosynthesis and what is produced, the atoms have just been rearranged and combined in a new way which creates a completely new substance.  Having students break apart the atomic make up of all of these to see a visual of how the arrangements have changed is important as a review for my students.  I have previously taught all of this and am making the connection to the new information on how it relates to glucose.  Reviewing when possible helps keep previously taught information fresh in their minds. 

                                               

I explain that this process that plants go through to make food is called photosynthesis.  Plants are also known as producers because they produce their own food which is the glucose or sugar used and stored as energy.  This is something other organisms are not able to do.  

Explore

30 minutes

Diagramming in Science Notebook:

As a review, I remind students that we have already witnessed solar energy being changed into other forms of energy.  In the experiment with the colored envelopes, solar energy was changed into thermal energy.  In the engineering project, solar energy was changed into electric energy that operated the solar cars.  Photosynthesis is a process where plants change solar energy into energy that is useful to them.  

Students take out their science notebooks and I place mine on the overhead as a model for students.  Projecting my notebook on the overhead is helpful for ESE and ESOL students but it is also helpful for students who struggle with spelling and for those who are visual learners. 

I title the page Photosynthesis and draw a large leaf in the center of the page.  I ask students to remind me of the three things plants take in for photosynthesis and they tell me sunlight, water, and carbon dioxide.  I draw three arrows pointing into the leaf and label each one with one of these items.  I explain that once the light energy is absorbed, it is transformed to a new type of energy, chemical energy.  The chemical reaction that occurs to break apart the bonds of the carbon dioxide and water, creates something new.  I then ask them what two items are created once the chemical energy breaks the bonds of the water and carbon dioxide and rearrange them.  Students tell me glucose and oxygen.  I draw one arrow going away from the leaf and label it is oxygen and then write on the leaf - sugar is stored in the leaf as food for the plant and animals that eat it.

                                                  

Making Photosynthesis Bracelets:  

I provide each group with a Ziplock bag that has 4 pieces of string with a knot already tied in one end, 4 green beads, 4 blue beads, 4 black beads, 4 yellow beads, 4 UV beads (looks clear), 4 pink beads, and 4 white beads.  These are the materials that will be needed to make the bracelets.  I tell them that each color of bead represents something in the process of photosynthesis.  I tell them to discuss with their group, the meaning of each bead, except the clear bead, and record their thoughts on a whiteboard.  I circulate to listen to the conversations and to get an idea of what each group will have recorded.  Once all groups are finished, I ask a couple of groups that had different ideas to share with the class.

I place the photosynthesis bracelet sheet on the overhead and show the top portion which shows the correct matching.  One group was able to get them all correct.  I instruct groups to take out the string and each student in the group to take one.  I then show the bottom portion of the photosynthesis bracelet, one line at a time, and have students create their bracelets as we go through each line.  After creating their bracelets, students help each other tie them to make a bracelet.

                                                

The bracelet helps students remember the steps by reading each bead across, beginning with the leaf.  I had students record on whiteboards a list of everything needed and created through photosynthesis after the lesson.  You can see in the video of student using the photosynthesis bracelet that the girl in the video is using the beads on her bracelet to help her group complete the list. 

Green - leaf is where photosynthesis occurs

Blue - water is absorbed through the roots

Black - Carbon dioxide is absorbed in the leaves

Yellow - light is absorbed in the leaves

UV bead - represents change that occurs in the leaf (this bead changes color so it is easy to remember)

Pink - Glucose (Sugar) the food that is stored and used as energy 

White - Oxygen that is released by the plant 

Wrap Up

10 minutes

Assessing with a Miniquiz:

I decide to assess with a photosynthesis miniquiz instead of an exit ticket or some other formative assessment because there are several things I want to assess understanding of.  Students are often assessed on photosynthesis using a diagram so I think seeing this in different ways is important.  I will continue to assess using a variety of diagrams.  I also want to check to see if students are able to make the connection to how animals get energy from plants, which was once energy from the sun, before I teach it directly.  This will be the next lesson in the unit.   

Results from Miniquiz

Almost every student was able to correctly answer the question on how animals get energy from the sun.  This tells me that I don' have to spend too much time teaching this in the following lessons, I can just continuously mention it throughout the lesson, focusing on those who did get it wrong to answer my questions.  

I found the results on the miniquiz to be very interesting.  Every student missed at least one, but there really was no consistency on what one was missed.  Those who performed very well at the bottom, missed something in the diagram at the top.  Those who got everything correct when labeling at the top, missed at least one at the bottom.  I have included some students work samples below.  

These two photos show works samples that have everything correct except one minor mistake. In the first picture, the student put that the item produced from photosynthesis, and stored in the leaf, is seeds.  I believe she put this because we had talked about the reproduction of plants the day before.  In the second picture, the student mixed up the oxygen, which is given off, and the sugar, which is stored in the leaf.  Small errors like this were made by most.