Teachers TryScience

Investigation 1
The Lesson Level Learning Goals for Investigation 1 are: Ask and answer questions to identify and clarify evidence that various activities can increase the carbon dioxide in the atmosphere and Analyze and interpret data to make a claim about a tree’s ability to store carbon. Students will build towards this goal by engaging with different phenomena.

First, students will figure out that plants absorb carbon dioxide from their environment by using an indicator tool to observe changes in carbon dioxide levels in a controlled environment.

Next, they will be introduced to a tool that they will then apply to collect quantitative data from a subset of local trees to identify characteristics that affect a tree’s ability to store carbon.

Student should be familiar with the following concepts before starting this lesson:

• The difference between climate and weather (3-ESS2-2)
• Respiration
• Photosynthesis

Investigation 1: Part 1

Materials

Bromothymol blue indicator solution
Water
Small jars (container) with lids
Straws
Pipette
Water plants (Elodea, etc.)
Goggles for students
Paper towels
Paper and pencil for students to record their observations
Timer, watch, or clock
Small air pumps

Preparation

For each student, mix a few drops of the indicator solution into a small jar or container of water just before class starts. The water should be a faint blue color.

You can provide students with a sheet on which they can record their predictions, observations, and data. In order for them to track changes in the Bromothymol blue solutions between the different steps, it may be helpful to include a table like the following to collect the qualitative color data. Instead, of giving students this pre-made table, this table can also be generated through a collaborative discussion with the class.

Background information for teacher

Bromothymol blue is a pH indicator solution that scientists use as a tool to observe changes in carbon dioxide levels in solution. As students exhale carbon dioxide into the cup of water, they will observe a change in color from blue to yellow

Instructional Sequence

• Begin by asking students to estimate how many trees they pass on their way to school. Can they recall passing any trees in particular? Do they pass by trees everyday without noticing them? Ask students how they think the number of trees in their local area might be similar or different from the number of trees in other communities throughout the country and across the world.
• Next, ask students to brainstorm some roles that trees play in the local ecosystem. Record their responses so that the class can refer back to them later. Tell students that they will be investigating this question in more depth throughout the next class period.
• Now, instruct students to find a partner and pass out pre-prepared jars of indicator solution (one for each student). Partners should determine whose jar is Jar One and whose jar is Jar Two. Have the students to take a moment to observe their cup. Students should write down their observations on a sheet of paper. They should record the solution color for their jar and their partner’s jar in their data table under “Initial Solution Color.”
• Pass out the straw and instruct students with Jar One to use the straw to gently blow into the solution for 30 seconds. Students with Jar Two should use a small air pump to gently blow air into their jar. (Safety Precaution: Tell students to be very careful not to suck the liquid up into their mouth.) You can time everyone together as a class, or have partners switch off timing and blowing into the jar. Once the allotted time has passed, have the students write down observations about their jars and share what they see. (They will have noticed that the solution has changed color from blue to yellow.) They should record the solution color for their jar and their partner’s jar in their data table under “Solution Color After Air.”
• Based on their observations, have the students discuss what they think was in the jar at the start? Use this conversation as a way to assess your students’ prior knowledge about respiration and carbon dioxide. If needed, prompt your students to think about what they exhaled out of their mouth and into the jar when blowing bubbles.
• After eliciting student responses about what was in the jar, you can tell students that the jar contained an indicator solution that scientists use as a tool to observe changes in carbon dioxide levels in solutions. The indicator solution changes color depending on the amount of carbon dioxide present in the solution. When they exhaled into the solution, they added carbon dioxide to the jar, causing the indicator to change color. The air from the pump did not add not more carbon dioxide to the jar. Be sure that students understand the difference between their respiration and the air pump.
• Ask students, “What color was the solution originally? What color did the solution change when you added more carbon dioxide into the solution?”
• Ask the students, “What do you think will happen to the color of the solution when we put a plant inside the jar?” Tell students that half of the students with Jar One will put a plant in their jar with the solution, and the other half of Jar One students will have just the jar with the solution and no plant. Students with Jar Two can set their jars aside.
• Have each student write down predictions about what will happen in each jar and their reasoning behind their predictions. Have some students share their predictions and reasoning. This is a good time to see what misconceptions students have and what they already know about plants and carbon dioxide.
• Have one student from each pair place a plant in their jar and the other partner leave their jar as is. Students should cover both jars and place them along a windowsill or other area with sunlight. Students should record their observations for both jars.
• Students must wait about 20 minutes (or until the next class period) before they can see results. (While you and your students wait, you can use this time at your discretion.)
• After students have waited the 20 minutes, instruct them to make observations about any changes to the solution in the cups and to record the solution color in the data table under “Solution Color After Adding Plant in Jar One.” Ask students to discus with their partners what they think happened over the past 20 minutes (or overnight). They will have observed that the cup with the plant indicates a decrease in carbon dioxide levels (it changed from yellow to a green-blue color) while the carbon dioxide levels in the control cup did not change. Ask them to use their results to write and support a claim (using their data and observations) about why the solution in the cup with the plant returned back to the original blue color. Discuss the claims as a class. If students are not familiar with supporting a claim using evidence, be sure to provide more guidance and support.
• Ask students to use their observations and background knowledge to again answer the question “What role do plants play in an ecosystem?” Ask students how their answers have changed from earlier in the investigation. Have the students share their ideas and thoughts. Also, take some time to have students generate a list of questions that they have at this point in the lesson. Build off some of their questions and thoughts as you transition to the driving question.
• Students will have figured out that plants take in carbon dioxide, so you can now introduce the lesson’s driving question: “What happens to carbon dioxide levels in a local community when trees are removed or added?” Tell them that for the rest of the lesson, they’ll be working to answer this question.

Investigation 1: Part 2

Materials

Photos of local trees
Copies of Carbon Sink Calculation Tool
Calculators
Tree Identification Resources (The teacher will need to collect the appropriate resources for their location. These can be online resources or physical tree identification guides.)
Copies of Observation Tool
Large flexible measuring tape
Other observation tools: Paper and pencils for bark rubbing, thermometers, etc.

Preparation

Prior to lesson, take pictures of trees around the school.

Background information for teachers

Hardwood vs. Softwood: The difference between hardwoods and softwoods is not based solely on how “hard” or dense a wood is. Instead, the classification is based on the structure of the wood. Hardwoods come from angiosperm trees (usually deciduous) and softwoods come from gymnosperm trees (usually conifers). This information is usually included in tree identification resources.

Carbon Sink Calculation: Scientists have determined certain statistical relationships between easy to measure traits of trees and some traits that might be more difficult to measure. The coefficients in the Carbon Sink Calculation Tool are the product of these relationships, and they allow us to identify a tree’s biomass without having to actually measure all of the tree’s biological material. These relationships differ based on the structure of the wood, so it is useful to use the hardwood vs. softwood classification system. You’ll notice that although students are measuring the trees’ diameter in centimeters, the final biomass is measured in kilograms. This change in unit is based on the predetermined statistical relationships.

In order for the class to figure out the role that tree species and size have on a tree’s ability to store carbon, you’ll need students to look at least 2 or 3 different tree species (or sizes). If your school is in a monoculture (an area where the trees are all the same species), you can give students additional sample measurements to use with the Carbon Sink Calculation Tool.

Instructional Sequence

• Show students pictures of different local trees to begin a discussion about how trees might differ from one another. Ask students “How are trees different?” and invite them to share what differences they observe in the photo and what differences have they observed in their own experiences. Students might cite differences in factors such as height, circumference, leaf shape, bark texture, color.
• Now ask students what might be some differences that they can’t immediately observe. After eliciting student responses, present students with the Carbon Sink Calculation Tool. Tell students that scientists use this tool to get a closer look beyond the surface observations that we’re able to make. You can refer back to the indicator solution from earlier in the lesson as another example of a tool that helps us make observations that aren’t possible otherwise. Take a moment to explain to students that the equations in this tool are not arbitrary. Rather, the scientific community has built up evidence about relationships between different factors that have allowed them to create these complex models of how factors like species and diameter interact. This type of empirically-based model is essential in helping us learn about things we can’t see or measure directly.
• Ask students to look closely at the equations, and ask them what parts of the necessary data can they collect. Can we directly measure diameter? If not, what can we measure? Is there other information that we would want to know? Make sure students understand all the components of the equations, what the components signify, and what components they will need to collect data for and why.
• Once students have generated a small list, tell them that they’ll be going outside to observe trees around the school. Tell students that they will be recording their data in their science notebooks. (Potential factors to record: environmental conditions, leaf collection, bark rubbing, etc. You can use the Observation Tool to help guide student observations or create your own observation protocol. In order to use the Carbon Sink Calculation Tool, students will need to record the trees’ circumference and species, so be sure that circumference and species are part of the observation students will be recording. Make sure students understand how to identify tree species using the Tree Identification Resources. They should be recording the name of the tree and then all of the observations associated with it. You can demonstrate protocols in the classroom or in the field depending on your classroom management style.)
• Have students go outside and gather qualitative and quantitative information about trees around the school. (Again, depending upon your management style, you can group students and have each group collect data about one specific variable, have each student collect a variety of measures, etc.)
• After students have returned to the classroom, give them more time to complete the calculations from the Carbon Sink Calculation Tool. Depending on how comfortable your students are with math and the calculations involved, you may want to walk through an example and/or provide additional support.
• Now have students work together to create a table to display the class data. At a minimum, the table should include tree species, diameter, and carbon storage.
• Now that students have gathered their data, ask them to look at the data and see if there are any trends or relationships between the variables. Encourage students to make statements based on their data.
• Once students have identified relationships (diameter and carbon storage capacity), have students create a graphical display of the data. Depending on your students, you may wish to provide support in the creation of the graphical display (i.e. discuss with them what type of graph to create, what the x and y variables are, etc.)
• Ask students “Based on the calculations and results, what statements can we make and what relationships can we identify? What does this data tell us in terms of carbon storage?” To support this, you can use a “What I See, What it Means” protocol. Students should create a T-chart and in one column, they should write statements about what they see (i.e. I see that as the diameter of the tree increase, the biomass also increases.) In the next column, students should interpret what their observations mean (i.e. Since biomass affects a tree’s ability to store carbon, trees with larger diameters can store more carbon than smaller trees of the same species.) Not every “I See” needs to match with a “What it Means”. Use their responses to guide instruction.
• After students have begun to think more deeply about the information they collected, prompt students to generate a list of wondering questions that may have arisen during data collection or analysis. After students have had time to work independently or in small groups, ask them to share their questions and record the questions on the board or chart paper.
• Ask students “Which of these questions can we answer with a simple Internet search, and which would require more investigation or research?”. Tell students that they will be looking into a question that requires more investigation.
• As a teacher, look at the narrowed list of investigation questions, and identify which questions might relate to the following prompt. Using the student-generated questions to build off of, introduce the question: “What role do different species and size trees play in the local environment?” If they need more prompting, ask students “Based on your data, make a claim about the relationship between the diameter of the tree and the tree’s ability to store carbon?” Have students work peer-to-peer to share their responses and get feedback on their claims, and then come back and discuss as a whole class.
• Using their T-chart of the data and their data analysis, students can figure out that a tree’s species and size affect its ability to store carbon and as diameter increases, carbon capacity increases.
• As you transition to the next investigation, use the class discussion to help students connect their findings to the amount of carbon dioxide a tree can store to the levels of carbon dioxide in the local environment.

Investigation 2

The Lesson Level Learning Goal for Investigation 2 is: Analyze and interpret local and national data to provide evidence that there is a relationship between the increase in carbon dioxide in the atmosphere and activities that result in the decrease of carbon sinks. Students will build towards this goal by comparing and contrasting data related to deforestation.

From Investigation 1, students figured out that since trees take in carbon dioxide, they can affect the amount of carbon dioxide in the environment. In this investigation, students will figure out that different activities can affect the number of trees in an environment. This will allow students to establish that removal or addition of trees can affect carbon dioxide in the environment.

Materials

Costa Rica Land Cover Figures
Copies of selected readings

Instructional Sequence

• Show students the Costa Rica Land Cover Figures (1940, 1961, 1977, 1997, 2005) from the “Forest losses and gains: where do we stand?” article. (These figures show a loss of tree coverage over time, with a slight recovery of forested area in the early 2000s.) Have students make specific statements (not inferences) about what they see.
  • http://www.unep.org/vitalforest/Report/VFG-02-Forest-losses-and-gains.pdf
• After students have shared their observations, provide students with context for the images by giving them the full article “Forest losses and gains: where do we stand?”.

Literacy Suggestions:

• Have students read the entire article and discuss as a group.
• Jig-saw the reading, by having students read assigned sections and share what they have learned with the rest of the students in the class.
• Have the students take notes, or highlight, or text code as they are reading.
• Encourage students to create a timeline of forest changes over time as they read through the article.
• Some students may require guiding questions. Consider the cognitive level of your students when developing guiding questions. Sample questions could include:
  • What is the author’s claim? What evidence do they use to support their claim?
  • How has tree coverage in Costa Rica change over time?
  • What activities have affected tree coverage in Costa Rica over time?
• After students have taken notes on the readings, engage students in a class discussion. You can use the questions presented in the literacy suggestions section to guide the discussion.
• Have students research data about deforestation in their local area. You can provide them the websites listed below as resources and may wish to guide them as to exactly what data they are looking for and want to record (i.e. any information regarding how tree coverage in the local area has changed over time, what has caused the change in tree coverage, etc.)

Additional Resources:

• You can also have students use the following interactive websites to explore tree coverage changes in their geographical area and elsewhere. http://earthenginepartners.appspot.com/science-2013-global-forest
  http://earthobservatory.nasa.gov/Features/WorldOfChange/hobet.php
• After students have had the opportunity to explore the Costa Rican data and their local data, ask them to analyze the data for any similarities or differences. What are the similarities and differences between Costa Rica’s deforestation data and the local deforestation data? What are the similarities and differences in terms of reforestation? Were the causes behind the tree coverage change similar or different? Why? Discuss their analysis as a class.
• Give students the following short readings. Instruct students to takes notes on each of the readings.
  • National Geographic Deforestation: http://environment.nationalgeographic.com/environment/habitats/rainforest-threats/ (This article will help students link changes in tree coverage to specific activities.)
  • WWF Deforestation: http://www.worldwildlife.org/threats/deforestation (This reading will help students link deforestation to changes in carbon dioxide emissions.)

Literacy Suggestions:

• Again, some students may require guiding questions. Consider the cognitive level of your students when developing guiding questions. Sample questions could include:
  • Compare the claims and evidence presented in both readings.
  • How can humans positively impact Earth’s forests
  • What is causing changes in tree coverage in the rainforest? How are these changes affecting Earth’s atmosphere?
• After students have taken notes on the readings, once again, engage students in a class discussion. You can use the questions presented in the literacy suggestions section to guide the discussion.
• Now that the students have more background resources and context, ask the students to make additional statements about what patterns they are seeing in the data. Ask them, “Based on this information, what effect can different activities have on carbon dioxide levels?”

Writing Task
The Lesson Level Learning Goal for this task is: Construct and present an oral and written argument supported by empirical evidence and scientific reasoning to support the claim that activities such as deforestation or reforestation can cause changes in the carbon dioxide in the atmosphere.

Students will figure out the relationship between different activities and changes in carbon dioxide in the atmosphere by writing an argument supported by empirical evidence and scientific reasoning. Additionally, they will use the evidence they’ve collected to outline a plan for their local community that includes plans for planting new trees and specifying why action can benefit the environment. They will use their evidence to explain which types of trees should be planted and why, and present their argument.

Materials

Copies of Writing Performance Task Rubric

Instructional Sequence

• Students will now take their observations and notes about the data and images and link them to the calculations they completed to help complete the writing performance task. Before presenting students with the writing task, take a few moments to facilitate a discussion that will allow students to synthesize the connections they have figured out in the investigations.
• Present students with the following Writing Performance Task.

Writing Performance Task: What happens to carbon dioxide levels in a local community when trees are removed or added?
Use the evidence (data) collected and scientific reasoning (resources) to outline a plan for your local community to decrease the amount of carbon dioxide in the atmosphere that includes instructions for planting new trees.

First, construct an argument that utilizes empirical evidence and scientific reasoning to support your claims that answer the following questions:

• How can trees affect atmospheric carbon dioxide?
• How can different activities affect trees?
• How can these activities affect carbon dioxide in the atmosphere?

Now propose a plan based on the claim you have made.

• Which types of trees should be planted in your community? Why?

Be prepared to present your claim and plan to the class.

• Before students begin working on their argument, ask students to share what they think constitutes a strong scientific argument. After a few responses, review the Writing Performance Task Rubric.
• If needed, provide additional support in the form of sentence starters such as My claim is ...., My evidence is… My reason is…. You could also work as a class to create a sample claim so that students have a better understanding of what is expected of them