We designed this resource for teachers who want to help their students learn about interdependent relationships in ecosystems. 

1. The food of almost any kind of organism can be traced back to producers such as plants and algae.
   • Food provides organisms the materials and energy they need to grow and function.
   • Producers make their own food inside themselves using energy from the sun, and matter from air and water.
2. Organisms in ecosystems are related in food webs.
   • Consumers get their food by eating other organisms. Some consumers eat producers. Some consumers eat other consumers.
   • Decomposers, such as bacteria, fungi, and earthworms, are consumers that break down dead organisms (or parts of organisms).
   • Decomposition eventually restores (recycles) some materials back to the environment, making necessary resources available to producers.
3. Organisms can survive only in environments in which their particular needs are met. Environmental conditions include, but are not limited to, light, temperature, moisture, amount of oxygen, nutrient availability, and salinity.
4. A healthy ecosystem is one in which the needs of multiple types of organisms are met in a relatively stable web of life.
5. Natural events and human activity can change the balance or stability of an ecosystem. When the balance, or stability, of an ecosystem changes, the opportunities for different types of organisms to meet their needs can increase or decrease.

Although the following DCIs are not the primary focus, they are also addressed within the resource:

PS3.D:  Energy in Chemical Processes and Everyday Life
The energy released from food was once energy from the sun that was captured by plants in the chemical process that forms plant matter (from air and water).

LS1.C:  Organization for Matter and Energy Flow in Organisms
Plants acquire their material for growth chiefly from air and water.

LS2.B:  Cycles of Matter and Energy Transfer in Ecosystems
Matter cycles between the air and soil and among plants, animals, and microbes as these organisms live and die.  Organisms obtain gases, and water, from the environment, and release waste matter (gas, liquid, or solid) back into the environment.

The resource is organized as a “driving question pathway,” focused on answering the question: Why are the fish dying in Sunrise Farm Pond?  Throughout, student learning is situated in this mysterious occurrence at Sunrise Farm Pond, which is presented to students as a story in three parts.  The story itself does not teach content, but rather motivates students to learn and understand the concepts addressed in the pathway in order to solve the mystery.  Students first learn that fertilizer has flowed from the Sunrise Farm fields into the pond and that fish in the pond have died.  Students will uncover the cause of the dead fish, which requires understanding organisms’ needs, abiotic factors, decomposition, and the interdependent nature of an ecosystem.  Equipped with these understandings, students can solve the mystery—fish are dying because the populations that the fish rely on for food have decreased due to a lack of oxygen.  The oxygen levels decreased because decomposers are consuming large amounts of dead algae (a process that requires oxygen).  The algae increased because of the additional nutrients introduced into the pond by fertilizer run-off.

The three parts of the pathway, each of which covers a different set of ideas, are structured in a sequence based on principles of effective science teaching (Banilower, Cohen, Pasley, & Weiss, 2010).  As students progress through “student experiences” (described in the next section) in each part of the pathway, they will discover the non-obvious, underlying reasons fish are dying.  The three pathway parts together represent the natural sequence of events that occurs when a pond is overloaded with nutrients.  Therefore, all parts should be included in instruction and done in order.

The sequence of events and underlying causes are depicted in this flowchart, intended for teacher reference.

Although the pathway centers on the story of Sunrise Farm Pond, many of the student experiences within each part of pathway engage students with phenomena (e.g., growth of producers, decomposition) outside the pond.  These experiences allow students to examine evidence that will deepen their knowledge of related concepts, which can be applied to the Sunrise Farm Pond mystery.

Each part of the pathway has a sequence of 4–6 student experiences, along with practical guidance for teachers, including:

• the purpose of each student experience;
• class discussion questions;
• relevant aspects of student thinking, such as common misconceptions; and
• implementation tips.

The information provided about student thinking alerts teachers to ideas (both correct and incorrect) their students may have or things to look for in their students’ work/responses.

Within each part, student experiences should be done in the sequence presented.  The sequence is designed to make students curious and then give them experiences to help them answer the driving question.

In addition to addressing disciplinary core ideas outlined in "The Science Content" section above, the pathway engages students in the science practices and incorporates crosscutting concepts.  Solving the mystery at Sunrise Farm pond requires that students develop a model and construct accompanying explanations supported by what they have learned about core ideas.

Within student experiences, relevant practices and crosscutting concepts are included as callout boxes (in blue and green, respectively), highlighting opportunities for bringing these practices and broader ideas to the forefront alongside the disciplinary core ideas. In addition, the "Navigating this Part of the Pathway" pages that precede each part of the pathway list the Student Experiences and include orange, blue, and green labels that link to the the NSTA K-12 progression for each designated DCI, Science Practice, or Crosscutting Concept.

Because it is important to develop students' understanding of crosscutting concepts over time and through multiple experiences, the following describes how the pathway as a whole develops these concepts.

Crosscutting Concepts

Patterns Throughout the pathway, students have multiple opportunities to observe patterns that they will later draw on when constructing an explanation of what is occurring at Sunrise Farm Pond.  It will be important for students to attend to patterns as they investigate conditions for organism growth (including algae growth in the pond water), and classify various organisms based on their knowledge of what the organisms need to survive.[/su_note]

Cause and Effect The pathway revolves around solving the mystery at Sunrise Farm Pond, which requires students to investigate causes, both direct and indirect.  Students use the model they develop over the course of the pathway to depict the relationships among biotic and abiotic entities in the pond.  Ultimately, they will draw on their knowledge of these causal relationships and their implications to solve the mystery at Sunrise Farm Pond.[/su_note]

Systems and System Models  Sunrise Farm Pond provides a real-world context for students to investigate eutrophication.  In the pathway, students remain focused on the pond system, which provides a venue for applying what they learn in various student experiences about producers, decomposition, and trophic relationships.  By the end of the pathway, students will have developed a model of the pond that represents its components (abiotic and biotic) and the interactions that they have gathered evidence for. In developing this model, students build an understanding of what has caused various changes in the Sunrise Farm Pond system.

Stability and Change  The mystery at Sunrise Farm Pond centers on an environmental disturbance.  By engaging in experiences in the pathway, students investigate components that have changed and the subsequent impacts.  After solving the mystery, students engage in discussion about what could be done to restore stability in the pond.

 

Part One of the pathway includes two experiments: observing algae growth in pond water and observing plants growing in different conditions.  Both experiments help students understand interdependence in ecosystems and need to be set up before students move on to the other student experiences in Part One and the rest of the pathway.  The descriptions for how to set up these experiments can be found on the “Preparing for the Mystery at Sunrise Farm Pond” pages.   Both experiments also require about three weeks of observations before students can begin to draw any conclusions.  To avoid a three-week gap in instruction, which may interrupt students’ focus on the content, the pathway describes how to set up these experiments before introducing the story of Sunrise Farm Pond.  That is, three weeks before beginning the student experiences of Part One, the teacher will set up the experiments and ask students to make observations daily.  Students should not receive any instruction related to interdependence during this three week interval (they can receive instruction on other science topics); the only thing they know is that they are writing down observations and they will discuss them at a later time.  This lack of discussion should also help to pique students’ interest in the pathway.  After three weeks of observations, students should have enough data to move forward with the remainder of Part One and begin to investigate the mystery at Sunrise Farm Pond.

Students’ engagement with the Sunrise Farm Pond scenario will be anchored in a cross-sectional illustration of a pond, which will ultimately be a well-developed model that explains what is causing the fish to die.  The pathway begins with students expressing their initial thinking about the organisms in the pond (using the cross-sectional pond drawing) and includes opportunities for students to revisit their thinking in each part of the pathway.  We recommend that teachers keep a record of previous versions so they can compare with their thinking at the end of the pathway.  (Students will likely need to make several changes, so we recommend starting a new drawing, as opposed to revising the previous version, in order to ensure clarity.)   Though it’s possible that students will add to their model throughout the pathway, the following student experiences explicitly ask them to make new drawings:

• Part 1: Student Experiences 2 and 5
• Part 2: Student Experience 5
• Part 3: Student Experience 4

Each experience involving the cross-sectional pond drawing is followed by a student experience that provides a portion of the storyline and gives students an opportunity to consider how the story relates to their drawing.

Click here to see a sample progression of the cross-sectional pond drawing throughout the pathway.  Note that these examples are meant for teacher reference.  We do not intend for you to show the examples to your students, nor should you expect your students’ models to include all of these components.

Click here to access a rubric for assessing student's models.  Please note that the rubric is intended to be use for formative purposes throughout the pathway to monitor student understanding and inform future instruction.

Our use of certain terms in this resource is quite purposeful.  We recommend that teachers model appropriate language usage to help students use terms appropriately for the science context.  The following are important cases to attend to.

• “Food” vs. “Nutrient” – These terms are considered interchangeable by many in everyday use. From an animal perspective, we may consider both to refer to what we eat.  In this resource, we restrict “food” to specifically mean the calorie-rich materials (e.g., sugars) that organisms use as energy sources.  Although producers don’t eat like animals do, they do need food in this sense (and make it themselves through photosynthesis).  “Nutrients,” on the other hand, are not calorie-rich materials but are important for other aspects of organism function.  Thinking of vitamins and minerals as nutrients may help make this distinction.  Like the components of fertilizer, vitamins and minerals are not food, but are required for healthy growth.
• “Eat” vs. “Consume” – We generally think of eating as the action of taking in food, which is appropriate for animals familiar to us, but does not apply to many other organisms that take in food. The bacteria that decompose dead algae are examples especially relevant to the Sunrise Farm Pond pathway.  They have no mouth or digestive system, but they do have ways of taking in food.  (The mechanisms by which bacteria “take in” food are complicated; we do not address them here because they are beyond what elementary students have the background to understand.)  In this resource, we use the term “consume” when referring to organisms, like the bacteria, that take in food from their environment but don’t actually eat.  The obvious relationship to “consumer” may help students understand the biological meaning of this term.
• “Organisms” vs. “Plants and Animals” – Many people, students and adults alike, often use “plants and animals” in everyday language as a term they intend to represent all organisms.  In fact, many organisms are neither plants nor animals.  Because this resource features the roles of such organisms (e.g., algae, bacteria), we recommend using the more inclusive “organisms” whenever referring to species other than plants and animals.
• “Plants” vs. “Producers” – Because plants are so familiar, some students may think that all producers are plants. Though plants are generally the most visible producers, many non-plant microbial species are also producers (e.g., photosynthetic algae and bacteria).  This distinction can wait until the term “producer” is introduced in Part One of the pathway.  Until that point, students may not have an understanding of producers, so using “plants” in place of “producers” may be necessary.   Because algae are central to the pathway and are non-plant producers, the distinction becomes important as the algae role unfolds in Part One.
• The term “ecosystem” is used in multiple ways in different contexts. In this pathway, ecosystem means the organisms and non-living components (e.g., rock, water, air, heat) in a particular setting.   An ecosystem also includes interactions among the living and non-living components in that setting.

We suggest introducing vocabulary to students within the context where the new terms naturally arise (like “plants” vs. “producers” above) rather than giving students a comprehensive vocabulary list.  Introducing each term as the need arises in context provides students an immediate basis for making the term meaningful to them.

We present an annotated version of the Sunrise Farm Pond story so that teachers can develop a firm grasp of its overall meaning before focusing on the individual parts of the pathway.  Our intention is that the notes provide helpful background information and elaborate on the science content incorporated into the story.  These notes contain information at a level beyond what a 5^th grade student is expected to know.  Students should be introduced to the story in the three parts of the pathway rather than seeing the whole story.  The version here is just for teachers.

The ecological process described in the story is called “eutrophication,” which stems from the Greek words eu (well) and trephein (nourish).  It is the process in which a body of water is enriched with an excess amount of chemical nutrients.  The increase in nutrients leads to a sharp increase in plant and algae growth and then a decrease in animal life.  For this reason, the process is also often called “nutrient overload” or “fertilizer overload.”

We have included time-lapse video with several of the long-term experiments.  These videos feature photos of the experiments taken once every minute over three weeks (excluding nighttime/dark).  Ideally, students will observe the actual phenomena firsthand in the classroom, but these videos can be used if results of the in-class experiments do not turn out as expected.  In situations where it is impossible to run in-class experiments, the time lapse video can be used instead; however, we strongly encourage you to do the experiments with students because the impact is greater.  Without these first-hand experiences, students may find it more difficult to understand and explain the processes involved.

Some of the experiments in the pathway could pose safety concerns if not handled appropriately. DO NOT INHALE OR INGEST MATERIALS USED IN THE EXPERIMENTS. For example, do not let students drink or touch the pond water in the jars during the Part One experiment.  Similarly, do not let students open the plastic bags storing the food for the experiment in Part Two; this step will help avoid inhaling mold spores.  Sealing the bags with tape will help ensure that students will not open the bags and should also help keep odors to a minimum.

The safety precautions described throughout this pathway are intended to serve only as a guide; the authors do not warrant that the precautions meet any safety code or standard of federal, state, or local regulations.  The authors disclaim any liability for personal injury or damage to property arising out of or relating to the use of this resource.