Ecosystems

Ecosystems is one of the six Carbon TIME units. If you are new to teaching Carbon TIME, read the Carbon TIME FAQ: Which Units Should I Teach.

The Ecosystems Unit supports students in using core disciplinary ideas, science practices, and crosscutting concepts to develop scientific explanations of how different ecosystems transform matter and energy as the organisms in them live, grow, and die.

Follow these steps to get ready to teach the Ecosystems Unit

Lead Editor for 2019 Version

Kirsten D. Edwards, Department of Teacher Education, Michigan State University

Principal Authors

Kirsten D. Edwards, Department of Teacher Education, Michigan State University

Joyce Parker, Earth and Environmental Sciences, Michigan State University

Craig Kohn, Department of Teacher Education, Michigan State University

Wendy Johnson, Kentwood Public Schools

Jenny Dauer, University of Nebraska, Lincoln

Elizabeth Tompkins, Michigan State University

Charles W. “Andy” Anderson, Department of Teacher Education, Michigan State University

Contributing Authors

Sarah Bodbyl Roels, Beth Covitt, Elizabeth Xeng de los Santos, Jennifer Doherty, Allison Freed, Bonnie McGill, Lindsey Mohan, Emily Scott, Carly Seeterlin, Nick Verbanic, Alex Walus

Illustrations

Craig Douglas

This research is supported in part by grants from the National Science Foundation: A Learning Progression-based System for Promoting Understanding of Carbon-transforming Processes (DRL 1020187) and Sustaining Responsive and Rigorous Teaching Based on Carbon TIME (NSF 1440988). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation or the United States Department of Energy.

Contact the MSU Environmental Literacy Program for more information: EnvLit@msu.edu.

The Driving Question

The Ecosystems Unit starts by asking students to express their ideas about the driving question about an anchoring phenomenon, “How many foxes can live in a meadow?”

Carbon is the key! In the unit, students learn to tell the story of how matter and energy are transformed as they move through ecosystems. A particularly powerful strategy for explaining how ecosystems transform matter and energy involves tracing carbon atoms. For more information about the Next Generation Science Standards disciplinary core ideas included in this unit see the sections on the Large Scale Four Questions below and the Unit Goals.

Research base. This unit is based on learning progression research that describes the resources that students bring to learning about plants and the barriers to understanding that they must overcome. It is organized around an instructional model that engages students in three-dimensional practices.

Students’ Roles and Science Practices

As students learn to answer the driving question by explaining how ecosystems transform matter and energy, they play three different roles that encompass all of the Next Generation Science Standards science and engineering practices. (For more details on science and engineering practices, see the Unit Goals.)

Questioners: Students explore the driving question, clarify, and generate more detailed questions
Investigators: Students conduct investigations using a simulation of a meadow ecosystem and develop evidence-based arguments about key observations and patterns
Explainers: Students construct model-based explanations of how carbon cycles and energy flows in different types of terrestrial ecosystems.

The roles that students play are embedded in the Carbon TIME instructional model and Discourse Routine. The Discourse Routine guides how classroom discourse aimed first at divergent thinking and then at convergent thinking should be sequenced through the unit.

Good Explanations Answer the Three Questions

Students figure out how to answer the driving question by tracing carbon-containing molecules through a series of movements and chemical changes as they travel through different matter pools in ecosystems. At each stage in these processes they answer Four Questions about what is happening: The Carbon Pools Question, the Carbon Cycling Question, the Energy Flow Question, and the Stability and Change Question.

Note that, in Carbon TIME, NGSS crosscutting concepts serve as the “rules of grammar” for producing a scientific performance. With respect to ecosystems, high quality explanations should attend to the following rules that are implied by crosscutting concepts. Explanations should attend to:

Scale by explaining events and phenomena at the appropriate scale (see more in the structure and function bullets below).
Systems and system models and energy and matter by following rules for tracing matter and energy through systems and system models. For example, neither energy nor matter should be created or destroyed as it moves into, through, or out of a system.
Structure and function by linking structures and functions in explanations at each scale.
- Ecosystem scale (tracing fluxes of carbon and energy through different matter pools in ecosystems)
- Macroscopic scale (tracing matter and energy through processes occurring inside plants, animals, and decomposers)
- Atomic-molecular scale (tracing matter and energy through chemical processes—photosynthesis, digestion, cellular respiration, and biosynthesis—involving molecules with different structures and properties)

The Carbon Pools Question: Where are the carbon pools in our environment?

Students learn to answer the Large-scale Four Questions for different ecosystems, beginning with the anchoring phenomenon of a meadow ecosystem as an example. They identify five carbon pools in each ecosystem.

Atmospheric carbon dioxide: the only inorganic carbon pool.
Producers: the organic carbon in plants and other photosynthetic organisms
Herbivores: animals that eat plants
Carnivores: animals that eat animals
Soil organic carbon: detritus such a fallen leaves, dead plants and animals, and decomposers that use organic materials in the soil as a food source

The Carbon Cycling and Energy Flow Questions: Explaining How Matter and Energy Move and Change in Ecosystems

Students begin the unit by investigating relationships among the sizes of carbon pools and find the pattern of relationships shown in Figures 1 and 2 above: The producer organic matter pool is much bigger than the herbivore pool, and the herbivore pool is much bigger than the carnivore pool.

Students learn to explain these patterns using carbon fluxes that move materials from one carbon pool to another. Carbon fluxes depend on processes, such as photosynthesis and cellular respiration, that take place inside individual organisms. They involve physical movement and chemical changes in matter, driven by changes in energy. Students study the carbon pools and fluxes shown in Figure 3 below.

The big picture: The left side of Figure 3 shows the general pattern of carbon cycling and energy flow in all ecosystems:

There are two big carbon pools: Carbon dioxide in the air and organic matter in living and dead organisms.
There are two big carbon fluxes: Photosynthesis changes carbon dioxide and water into organic carbon and oxygen; cellular respiration completes the cycle, turning organic carbon and oxygen back into carbon dioxide and water.
Energy flows through the ecosystem: Sunlight is converted into chemical energy in organic matter, which is released through cellular respiration, ultimately becoming heat that the Earth radiates into outer space.

Details of organic matter pools and fluxes: The right side of Figure 3 shows details of pools and fluxes inside the large organic matter pool. Food chains and food webs are a part of this story, but not the whole story. Plants use the organic materials that they create with photosynthesis for growth and energy (cellular respiration). The materials in plant bodies move to other pools when the plants are eaten or when dead plant materials become detritus in the soil. Ultimately organic materials are oxidized to carbon dioxide and water through cellular respiration in plants, animals, and decomposers. [1]

[1] Some soil carbon can remain in the soil for a very long time, ultimately becoming fossil fuels. These processes are discussed in the Human Energy Systems Unit.

The Stability and Change Question: How do carbon fluxes change the size of carbon pools?

(Note: The Stability and Change Question is addressed mostly in Lesson 4, which is optional for middle school students since modeling of processes that change ecosystems is addressed primarily in NGSS High School Performance Expectations—see the Unit Goals tab.)

Ecosystems are constantly changing. Students learn to analyze how changes in ecosystems affect carbon pools and fluxes using quantitative online models (illustrated in Figure 4 below) and by studying cases of different ecosystems.

Students analyze how carbon cycling and energy flow are affected by three kinds of changes in ecosystems:

Seasonal changes affect the photosynthesis flux in particular, changing the balance of fluxes and the sizes of the organic matter and CO₂
Human management in ecosystems such as farms and ranches: Humans alter the environment so that ecosystems produce goods and services that we need.
Disturbances such as fires and droughts change carbon fluxes and carbon pools.

How Much Detail?

There are more complicated and more scientifically accurate ways of talking about chemical bonds and about changes in energy; we discuss some of those in detail in our educator resource: Carbon TIME Carbon TIME Content Simplifications. But our learning progression research has shown that there is an important tradeoff here—many students get lost in the details and never learn a basic coherent story that answers the driving question. The Next Generation Science Standards take a clear position on this tradeoff; a coherent story based on principles such as matter and energy conservation is more important than the details. Consult the Unit Sequence tab and the sections on Extending the Learning at the end of each Activity page to decide how much detail is appropriate for your students.

Before beginning the Ecosystems Unit, you need to decide what to teach and importantly, what not to teach! Use this page to choose the unit sequence that’s most appropriate for your students.

Some activities are TWO-TURTLE ACTIVITIES (), which place a higher demand on students. Decide whether the higher demand required by these activities will be useful or distracting for your students. The Carbon TIME Turtle Trails Document document provides further info about choices for making units more or less demanding, depending on your students’ needs.

Unless otherwise noted in the table below, all activities in the unit should be taught.

Ecosystems Unit Sequence and Decisions Table

Here, we present two ways to think about how lessons are sequenced in the Ecosystems Unit. The Instructional Model, immediately below, emphasizes how students take on roles of questioner, investigator, and explainer to learn and apply scientific models they can use to answer the driving question. Further below, the Unit Storyline Chart highlights the central question, activity, and answer that students engage with in each lesson of the Ecosystems Unit.

Instructional Model

Like all Carbon TIME units, this unit follows an Instructional Model (IM) designed to support teaching that helps students achieve mastery at answering the driving question through use of disciplinary content, science practices, and crosscutting concepts. To learn more about this design, see the Carbon TIME Instructional Model.

During the inquiry portion of the unit (Lesson 2), the students move from making observations of a simulated meadow ecosystem to identifying patterns, eventually using these patterns to make evidence-based arguments. During the explanation portion of the unit (Lessons 3, 4, and 5), students makes connections across scales (from atomic-molecular scale to ecosystem scale) to explain patterns and changes in ecosystems. Across the unit, classroom discourse is a necessary part of three-dimensional Carbon TIME learning. The Carbon TIME Discourse Routine document provides guidance for scaffolding this discourse in lessons.

The core of the Carbon TIME IM is the Observation, Patterns, Models (OPM) triangle, which summarizes key aspects to be attended to as the class engages in unit inquiry and explanation. The OPM triangle for the Ecosystems Unit, shown below, articulates the key observations students make during the unit investigation, the key patterns they identify through analyzing their investigation data, and the central scientific model that can be used to answer the unit’s driving question.

Observations, Patterns, Models, and Explanations in the Ecosystems Unit

Unit Storyline Chart

Another way to familiarize yourself with the sequence of lessons in the Ecosystems Unit is with the Unit Storyline Chart depicted below. The Unit Storyline Chart summarizes a unit phenomenon-based driving question associated with each lesson, what classes will do in each lesson to address the question, what conclusions they will come to, and how they will transition to a subsequent lesson.

Download Unit IM and Storyline Chart

The tables below show goals for this unit in two forms. A list of Next Generation Science Standards (NGSS) addressed by this unit is followed by a table showing specific target performances for each activity.

Next Generation Science Standards

The Next Generation Science Standards (NGSS) Performance Expectations that middle and high school students can achieve through completing the Ecosystems Unit are listed below. To read a discussion of how the Carbon TIME project is designed to help students achieve the performances represented in the NGSS, please see Three-dimensional Learning in Carbon TIME.

High School

Ecosystems: Interactions, Energy, and Dynamics. HS-LS2-1. Use mathematical and or computational representations to support explanations of factors that affect carrying capacity of ecosystems at different scales.

https://www.nextgenscience.org/pe/hs-ls2-1-ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy, and Dynamics. HS-LS2-2. Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and populations in ecosystems at different scales.

https://www.nextgenscience.org/pe/hs-ls2-2-ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy, and Dynamics. HS-LS2-3. Construct and revise an explanation based on evidence for the cycling of matter and flow of energy in aerobic and anaerobic conditions.

https://www.nextgenscience.org/pe/hs-ls2-3-ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy, and Dynamics. HS-LS2-4. Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.

https://www.nextgenscience.org/pe/hs-ls2-4-ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy, and Dynamics. HS-LS2-5: Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere.

https://www.nextgenscience.org/pe/hs-ls2-5-ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy, and Dynamics. HS-LS2-6: Evaluate claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.

https://www.nextgenscience.org/pe/hs-ls2-6-ecosystems-interactions-energy-and-dynamics

Earth’s Systems. HS-ESS2-6. Develop a quantitative model to describe the cycling of carbon among the hydrosphere, atmosphere, geosphere, and biosphere.

http://www.nextgenscience.org/hsess-es-earth-systems

Middle School

Matter and Energy in Organisms and Ecosystems. MS-LS1-6. Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy in and out of organisms.

http://www.nextgenscience.org/msls1-molecules-organisms-structures-processes

Matter and Energy in Organisms and Ecosystems. MS-LS2-1. Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.

http://www.nextgenscience.org/msls2-ecosystems-interactions-energy-dynamics

Interdependent Relationships in Ecosystems. MS-LS2-2. Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems.

http://www.nextgenscience.org/msls2-ecosystems-interactions-energy-dynamics

Matter and Energy in Organisms and Ecosystems. MS-LS2-3. Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.

http://www.nextgenscience.org/msls2-ecosystems-interactions-energy-dynamics

Matter and Energy in Organisms and Ecosystems. MS-LS2-4. Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.

http://www.nextgenscience.org/msls2-ecosystems-interactions-energy-dynamics

Earth’s Systems. MS-ESS2-1. Develop a model to describe the cycling of earth’s materials and the flow of energy that drives this process.

http://www.nextgenscience.org/msess-es-earth-systems

Human Impacts. MS-ESS3-4. Construct an argument supported by evidence for how increases in human population and per-capita consumption of natural resources impact Earth’s systems.

http://www.nextgenscience.org/msess-hi-human-impacts

Target Performances for Each Activity

All Carbon TIME units are organized around a common purpose: assessing and scaffolding students’ three-dimensional engagement with phenomena. Every Carbon TIME activity has its specific expectation for students’ three-dimensional engagement with phenomena, what we call its target performance. Each activity also includes tools and strategies that teachers can use to asses and scaffold the target performance in rigorous and responsive ways.

The target performances for each activity in the Ecosystems unit are listed in the table below.