Understanding Causal Relationships in Food Webs

Marin E. Silva, April C. Maskiewicz
Type Category
Instructional Materials
Activity , Article , Lesson/Lesson Plan
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



This article in the October 2016 issue of The American Biology Teacher uses five interrelated  “data-rich problem” tasks to help students make sense of the phenomenon of species loss within the context of a marine ecosystem. By using the “Learning-for-Use” framework (described in the article), each task is designed to help students construct their own understanding of the complex relationships that may all be impacted by a disturbance. As students engage in the different tasks, they have opportunities to develop and use a variety of science and engineering practices and crosscutting concepts. The authors’ goal is for students to become citizens that can make informed  and sustainable decisions about issues that impact ecosystems. The actual tasks  may be found at: https://sites.google.com/site/marineecosystemdrptasks/

Intended Audience

Educational Level
  • High School
Access Restrictions

Available by subscription - The right to view and/or download material, often for a set period of time, by way of a financial agreement between rights holders and authorized users.

Performance Expectations

HS-LS2-6 Evaluate the 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.

Clarification Statement: Examples of changes in ecosystem conditions could include modest biological or physical changes, such as moderate hunting or a seasonal flood; and extreme changes, such as volcanic eruption or sea level rise.

Assessment Boundary: none

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
Tasks 3-5 (Day 3, 4, and 5) all involve students considering the impact of change on the marine ecosystem. Using actual data, and then making estimates of how changes may impact a variety of species within the marine ecosystem, students predict whether or not the marine ecosystem will be stable or become a new ecosystem. As the authors suggest, teachers may want to encourage students to think about how any disturbance affects all of the species within an ecosystem - not just the species that appears the most affected by the particular disturbance. Teachers need to be sure that students are considering the full complexity of all the relationships within the food web.

HS-LS2-2 Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and populations in ecosystems of different scales.

Clarification Statement: Examples of mathematical representations include finding the average, determining trends, and using graphical comparisons of multiple sets of data.

Assessment Boundary: Assessment is limited to provided data.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
Being data-rich tasks, each one has contextualized information about the marine ecosystem in some form of mathematical representation. High school teachers can enhance this aspect by asking students to graph the data as part of their analysis. All throughout the different tasks, students use the data to support and revise their explanations. In this way, they are using the data as evidence to support and revise their explanations. Teachers may want to focus on the “Learning for Use” framework which includes the three steps of motivate, construct, and refine so that students can deepen their understanding of the materials in each task. Although students may want to bring in outside knowledge they may have about the different organisms within the marine ecosystem, it is important to emphasize the importance of providing evidence to support their explanations.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Throughout the tasks, students have opportunities to evaluate the claims, reasoning, and evidence behind their own and peers’ explanations. For example, in task 4, the authors recommend that students pair with other students from different teams to present their arguments to one another, one on one. A whole-class discussion follows, which helps to resolve any conflicts and answer any remaining questions. Through this practice, which is repeated in other places, students gain experience in scientific argumentation, leading to understanding of the phenomenon. As mentioned previously, it is important that students use the data as evidence to support their claims and not just their understanding from previous reading or experience with the marine ecosystem.

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Teachers will want to encourage students to engage fully with the data provided in the tasks. If students are interested, it may also be valuable for them to do additional analyses of the data and to represent it in different formats, or even to consider other sources of similar data. As mentioned earlier, high school teachers may want to ask students to graph the data. The authors make the comment that some students forget the context and focus on the numbers. It is very important to keep the students aware of the context of the data. In the “Day 1: Food Chain Comparison” task, teachers may want to note that the provided energy values represent the approximate energy units per gram that are transferred from one trophic level to another.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
Research about student understanding of ecosystems reveals that many students reach high school and college with a simple, linear view of ecosystem relationships. Teachers will want to continually encourage students to consider the complexity of relationships within the marine ecosystem presented in the tasks. The authors suggest that each task be followed by a whole-class sense-making discussion. These discussions are critical to the students’ success in developing their understanding of this disciplinary core idea.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
Students have multiple opportunities to develop and use this crosscutting concept throughout the five tasks. However, teachers may want to optimize the opportunity in the last task to emphasize it. In this task, a disturbance occurs, and students look at the large data set and complex relationships to determine what the outcome will be ten years later. Teachers may want to encourage students to consider whether the ecosystem will remain the same or change. If it does change, students will need to consider whether or not it is still the same ecosystem or a new one. For all of the tasks, teachers will need to be listening and observing students to be sure that they are considering this crosscutting concept.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This series of five tasks does an excellent job of providing opportunities for students to engage in three dimensional learning as they makes sense of the phenomenon of species loss within a marine ecosystem. Students use representations of real data from a marine ecosystem as they evaluate the claims, evidence, and reasoning of their own and other peer groups. They have opportunities to revise their explanations while they communicate with other team members about their thinking. By the completion of the tasks, students are asked to predict whether or not the ecosystem is stable or has become a new ecosystem. They must use evidence to support their reasoning. Upon completion of all tasks, students have gained an understanding of the complex causality of species loss on an ecosystem.

  • Instructional Supports: Students engage with real data about a very relevant phenomenon as they actively use science practices. Teachers may want to adapt the tasks to a locally-relevant ecosystem to enhance the relevance for students who do not live in the Pacific coast region. Students have many opportunities to collaborate with their peers and to engage in meaningful discussions. The data provided is scientifically accurate and grade-appropriate. Suggestions are made throughout the tasks for ways that teachers can differentiate instruction and extend the tasks for highly motivated students. There are many helpful prompts suggested to teachers for students who may not see the complexity or who may forget the context of the data. Appropriate modifications are also suggested for high school students.

  • Monitoring Student Progress: As mentioned throughout this review, students have many opportunities to provide observable evidence of their three-dimensional learning. Suggested questions are provided, as well as an assessment that may be given at the end of the tasks completion. No scoring guidance is provided.

  • Quality of Technological Interactivity: This lesson does not use technology.