MnSTEP Teaching Activity Collection > MnSTEP Activities > Investigating Ecosystems: Determining Feeding Relationships among Organisms

Investigating Ecosystems: Determining Feeding Relationships among Organisms

Anna Potvin, Pine City Secondary, Pine City, MN


In this life science field lab, students will complete a field study in and around either their schoolyard or home. Students will make observations, generate questions, design an investigation about feeding relationships between organisms based on their questions, collect data/make more observations, and present their findings in a food web as well as in a written narrative.

Learning Goals

At the completion of this activity, students will be able to:
- make thorough observations of a living system
- synthesize testable questions about that living system using the observations made
- design an investigation to answer the question posed
- construct and interpret food webs
- develop new, testable questions to further their investigations

Vocabulary to be introduced or reinforced: ecosystem, trophic level, producer, consumer (primary, secondary, tertiary), carnivore, herbivore, omnivore, scavenger, decomposer, energy source, food web, energy pyramid

Context for Use

This plan is intended for a tenth grade biology class, but it could be easily adapted to fit into the seventh grade life science curriculum as well. Classes meet everyday in 50-minute class periods. This is a field investigation that will be complemented with periodic lecture, and it is designed to be an extended project to start the year in biology. Materials needed include insect collection nets, kick-screens, collection containers, forceps, labels, field guides, dichotomous keys, microscopes, and hand lenses. Before beginning the field study, students should have the following skills set:
- ability to make quality observations with words and pictures
- ability to distinguish living things from non-living
- ability to use field guides and dichotomous keys to identify unknown organisms
- ability to use microscopes

Subject: Biology:Ecology:Food Webs
Resource Type: Activities:Field Activity
Special Interest: Field-Based Teaching and Learning
Grade Level: High School (9-12)
Theme: Teach the Earth:Enhancing your Teaching:Teaching in the Field

Description and Teaching Materials

1. Begin activity by instructing students to go into the field individually and make observations in their science notebooks of as many living things as possible. Observations should include the following:
o written descriptions
o drawings
o pictures
o collections of plant/animal/water samples may also be made

Tell students that they should make as detailed observations as possible, because they will be required to identify all of the organisms eventually. A drawing of each organism will also be required.

At this level, students may choose the area they would like to observe. Students may choose an area surrounding the school or somewhere near their home.

2. In groups, students will share their observations. Groups will then share their overall findings with the entire class. We will discuss the kind of organisms they found and whether they are able to identify them all. If students are general with their observations (trees, insects, birds, etc), explain that there are different types of each of those and that it will be important to identify the specific kind for our investigation.

In groups, students will then come up with questions they may have about the organisms they observed. They will write their questions on whiteboards to share with the class. If they have not come up with the following questions, I will pose them:
o What kinds of things do these organisms need to survive?
o How do they get their energy/food?
o Are any of these organisms related? If so, how?

Explain that all of the questions that were generated are good questions, but for our purposes, we are going to focus on the above questions.

3. Introduce food web vocabulary (listed above in goals).

4. Instruct students to again make observations of their ecosystem. This time, they need to be sure to have enough information to identify them by their common name.

Students will use resources available to them (microscopes, hand lenses, field guides, dichotomous keys, and internet) to identify each organism in their ecosystem. For organisms that can be collected and brought into the classroom to identify (macroinvertebrates, tree leaves, etc), students will be encouraged to do so. For organisms that are too large to bring into the classroom, students will be required to draw a picture detailed enough to use for identification purposes.

Students will also use available resources to determine the energy source(s) of each organism identified.

5. Instruct students to organize their data and create a visual representation (food web) of the feeding relationships. The food web should include detailed pictures of each organism, as well as the name of the organism.

6. Bring data together to create a large food web based on class data.

7. Students will write a narrative in their science notebooks explaining their food webs and the feeding relationships they identified. They will hypothesize what might happen to the populations of organisms if a new organism is introduced or if an existing population is eliminated. In their narratives, students will also reflect on their investigations and formulate new questions they have about the ecosystem they studied.

Teaching Notes and Tips

This activity is an adaptation from a previous insect collection activity in which the students were required to collect, pin, and identify twenty insects. Because the insect collection assignment was not an investigation but rather a simple task, and also because it does not cover any current science standards, I felt obligated to change it to a more worthwhile experience for my students.

This activity could be adapted in a number of ways to make it more or less challenging. If the teacher wanted more control over the field study, s/he could require all observations to be made at the same place on or near the school property. All observations could even be made during class time. Students can work independently or in groups, depending on the preference of the teacher, and students could also be given more freedom as to the type of question they investigate.

As the year progresses, this project can be referenced when talking about symbiotic relationships, effect of human activity on ecosystems, change over time, and much more.


1. Students will turn in their science notebooks with all observations and notes from their field study. These will be graded on completion and quality of observations.

2. The student-generated food webs (see #5 in Teaching Notes) will be graded on accuracy.

3. Student narratives (see Teaching Notes #7) will be turned in and graded.

Standards Design and conduct an experiment. Explain how matter and energy in an ecosystem is transformed and transferred among organisms.

References and Resources