Grade 7

Lesson Plan


The student will determine the overall quality of a stream using indicator species as a measure.

(PA Science & Technology Standards: 3.1.7B, 3.2.7B, 3.7.10A; PA Environment & Ecology Standards: 4.1.7B, 4.1.7C)

The student will develop an hypothesis to explain why some living things are indigenous to certain types of environments.

(PA Science & Technology Standards: 3.2.7B, 3.2.7C, 3.3.7A, 3.3.7D; PA Environment & Ecology Standards: 4.1.7C, 4.6.7A)

The student will evaluate the usefulness of indicator species as a tool for water quality measurement.

(PA Science & Technology Standards: 3.2.7C, 3.7.10B, 3.8.7C; PA Environment & Ecology Standards: 4.3.7C)

Process Skills:

Observing, Inferring, Predicting, Measuring, Interpreting Data, Formulating Hypotheses, Experimenting, Solving Problems


Materials: (For each student)

Collection bottles


Yardstick or metal tape measure

Identification Guide (shared)

Natural stream (accessible to class groups)

Predicting Organisms activity sheet

Stream Survey Data chart

Indicator Species activity sheet

Time Requirement:

135 minutes (or three class sessions)


Pre-planning: Prior to this stream survey activity, ask students to complete the Predicting Organisms activity sheet. They will predict the kinds of organisms and the relative numbers of each they would expect to find in a "clean" stream. They will make the same predictions for a stream in unhealthy condition.

1. Ask the students to develop an hypothesis that identifies the most important limiting factor for stream organisms. (Teacher Note: Limiting factors are environmental conditions that limit how much a population can grow. Limiting factors of animals include temperature, weather, water, food supply, and shelter.)

2. Over a two-day period, take students to a nearby natural stream. Using the Stream Survey Data activity sheet, direct them to record general stream conditions (weather, stream temperature, stream flow rate, turbidity, and cover) on the date they place their collection bottles and on the date they retrieve their collection bottles.

3. Direct students to place collection bottles at one or more different sites. (Teacher Note: The number of collection bottles can be adjusted based on number of students, supply of collection bottles, size of collection bottles, etc. If necessary, students can work in pairs or groups sharing a set of collection bottles, as long as each student has an opportunity to collect and analyze data.) They should measure and record the stream depth at each of ten sample sites and calculate the average stream depth. Students should also measure the average width of the stream at each of ten sample sites and calculate the average stream width.

4. When the collection bottles are retrieved, direct students to identify and count the living organisms that are present in all of their collection bottles and record their findings in the spaces provided on the Predicting Organisms activity sheet. Students will need to have access to Identification Guides in order to correctly identify unfamiliar organisms.

5. Ask students to determine the relative health of the stream using a teacher-prepared key as a reference.

6. Ask students to evaluate whether their data support or refute their prediction of the most important limiting factor.


Accuracy of Stream Survey Data chart

Response to journal prompts

Lesson Extension:

Have students conduct chemical tests on water samples taken from the same natural stream. Ask them to evaluate the strengths and weaknesses of chemical tests of water quality.

Ask students to compare chemical testing with use of indicator species as a measure of clean water. Have them work in teams debating the superiority of one method over the other. Alternatively, they could write a persuasive essay in support of the type of test (chemical or indicator species) that would be best suited to test the drinking water coming to their homes.

link to PREDICTING ORGANISMS Activity Sheet

link to STREAM SURVEY DATA Activity Sheet

link to INDICATOR SPECIES Activity Sheet

Branching Out

Student Resources


Teacher Resources


Related Pennsylvania Resources