"Identifying Macroinvertebrates" Lesson Plan

Keywords: macroinvertebrates, dichotomous key
Prepared by: Kristina Rogers, Loyalsock Township High School
Lesson Plan Grade Level: seventh through ninth grade
Total Time Required for Lesson: 90-minute continuous block
Setting: classroom
Subjects Covered: biology, environment, and ecology
Topics: importance of macroinvertebrates and using dichotomous keys

Goals for the Lesson

• Students will be able to define what macroinvertebrates are.
• Students will be able to use a dichotomous key to identify macroinvertebrates.
• Students will be able to describe the environmental value of specific macroinvertebrates.

Materials Needed

• Critters Fact Sheets: Caddis Flies class set : available from the PA Fish and Boat Commission
• macroinvertebrate handout
• dichotomous key (class set) (available online at: http://wsrv.clas.virginia.edu/~sos-iwla/Stream-Study/Key/MacroKeyIntro.html or can be ordered through Save Our Streams)
• references on aquatic macroinvertebrates (for example: Save our Streams Monitor's Guide to Aquatic Macroinvertebrates, available to order from http://wsrv.clas.virginia.edu/~sos-iwla/Stream-Study/StreamStudyHomePage/Information.html), one per group
  

State Standards Addressed: E & E Standards: Watersheds and Wetlands (4.1.7 C, 4.1.10 C); Biology (3.3.7 A); Earth Science (3.5.10 D)

Teaching Model: Lecture, Cooperative Learning, Presentations

Methods

1. Introduce and define macroinvertebrates.
   
   • Distribute a Caddis Fly fact sheet to each student and discuss basic macroinvertebrate structure and life stages. Discuss basic facts about macroinvertebrates, giving definitions, examples, discuss different roles such as shredders, decomposers, etc.
     
2. Discuss the importance of macroinvertebrates; some or all of the following could be discussed:
   
   • Stream-bottom macroinvertebrates are an important part of the community of life found in and around a stream.
     
   • Stream-bottom macroinvertebrates are a link in the aquatic food chain. In most streams, the energy stored by plants is available to animal life either in the form of leaves that fall in the water or in the form of algae that grows on the stream bottom. The algae and leaves are eaten by macroinvertebrates. The macroinvertebrates are a source of energy for larger animals such as fish, which in turn, are a source of energy for birds, raccoons, watersnakes, and even fishermen.
     
   • Stream-bottom macroinvertebrates differ in their sensitivity to water pollution. Some stream-bottom macroinvertebrates cannot survive in polluted water. Others can survive or even thrive in polluted water. In a healthy stream, the stream-bottom community will include a variety of pollution-sensitive macroinvertebrates. In an unhealthy stream, there may be only a few types of nonsensitve macroinvertebrates present.
   • Stream-bottom macroinvertebrates provide information about the quality of a stream over long periods of time.
   • It may be difficult to identify stream pollution with water analysis, which can only provide information for the time of sampling. Even the presence of fish may not provide information about a pollution problem because fish can move away to avoid polluted water and then return when conditions improve. However, most stream-bottom macroinvertebrates cannot move to avoid pollution. A macroinvertebrate sample may thus provide information about pollution that is not present at the time of sample collection.
   • Stream-bottom macroinvertebrates are relatively easy to collect.
     
   • Useful stream-bottom macroinvertebrate data are easy to collect without expensive equipment. The data obtained by macroinvertebrate sampling can serve to indicate the need for additional data collection, possibly including water analysis and fish sampling.
     
3. Introduce and practice using a dichotomous key.
   • Explain the importance and use of a dichotomous key, show examples of various keys to the class. Construct a classroom dichotomous key together with the class using a few students or a few simple objects. After you have constructed the key work through the key with the class to identify the objects.
4. Group work: Identifying macroinvertebrates and their importance.
   
   • Break class into groups with three or four students per group.
   • Distribute the macroinvertebrate handout, dichotomous keys, and reference materials.
   • Explain to the students that they will use their keys and reference material to identify and describe the importance of each macroinvertebrate. Students should work together in their groups to complete the worksheet. Depending on time limits or class size, groups could be assigned specific macroinvertebrates to research and then present their information to the class.
     

Evaluation

• Students should be able to use a dichotomous key to identify macroinvertebrates.
• Students should be able to identify a few pollution tolerant and intolerant species. These behaviors could be evaluated by doing a sample or actual stream study of aquatic macroinvertebrates allowing students to use a dichotomous key and note sheets.

References

Issac Walton League of America. Save Our Streams.

Kellogg, Loren Larkin (1992). Save Our Streams Monitor's Guide to Aquatic Macroinvertebrates. Izaak Walton League of America. This booklet is the source of most of the information provided by the Stream Study Web site, including the macroinvertebrate identification key and many of the line drawings.

Pennsylvania Fish and Boat Commission Web site

Background information on importance of macroinvertebrates