Introduction

This activity allows students who have gained experience in Berlese funnel extraction of microarthropods ("Microarthropod Collection and Examination") and microarthropod identifications ("Microarthropod Variation and Taxonomy") the opportunity to take part in the steps that actual scientists go through in their own work. Students begin with online reading and an online literature search to better understand the use of population indices in biological investigations. They follow with writing a brief proposal for their own investigation, melding their skills in microarthropod extraction and classification with an independent investigation involving quantitative arthropod ecology study.

Grade Level of Participants

This set of activities is quite suitable for high school students. Teachers of introductory courses may select components of this activity, while teachers of juniors and seniors may want to incorporate all of the components, essentially taking students through a modified version of all of the steps scientists typically follow in their professional work.

Duration Of Activity

The full range of activities presented will take the equivalent of five to six full class periods to complete. Internet component activities (search plus write-up) will take about two class periods, the proposal writing component will take a minimum of a full class period, with a half class period required for the rewrite. Collection of samples will likely occur at home or after school. Berlese set-up will take another half class period, with classification and data analysis taking an additional class period. Most likely the teacher will assign the final write-up as homework. This project is well-suited to class presentations, which will require additional class time, but are often well worth the time investment.

Curriculum Connection

This activity works integrates well into class coverage of topics including ecology, organismal diversity and field methodology. It is an excellent activity in making clear the steps involved in the scientific investigation process and culminates in a quantitative study, something which often doesn't occur in traditional biology classroom investigations. I highly recommend that teachers incorporating this activity into their classroom read through the last of the online resources presented at the end of this page, as well as its accompanying linked pages, to supplement their own background. Reading of one or more of those pages may be useful to high school students prior to development of their own experimental protocols.

Linkage to National Science Standards - AAAS Benchmarks

The following AAAS Benchmarks are addressed through "Microarthropod Collection and Examination". Each knowledge or skill benchmark below pertains to students in grades 9-12. Each knowledge or skill benchmark is presented by topic chapter number and section, section title and section benchmark. The entire text of the AAAS document can be accessed at Benchmarks On-Line.

12B. Computation

By the end of the 12th grade, students should be able to

• Use ratios and proportions, including constant rates, in appropriate problems.
• Find answers to problems by substituting numerical values in simple algebraic formulas and judge whether the answer is reasonable by reviewing the process and checking against typical values.
• Make up and write out simple algorithms for solving problems that take several steps.
• Use computer spreadsheet, graphing, and database programs to assist in quantitative analysis.
• Compare data for two groups by representing their averages and spreads graphically.
• Express and compare very small and very large numbers using powers-of-ten notation. Trace the source of any large disparity between an estimate and the calculated answer.
• Consider the possible effects of measurement errors on calculations.

12C. Manipulation and Observation

By the end of the 12th grade, students should be able to

• Learn quickly the proper use of new instruments by following instructions in manuals or by taking instructions from an experienced user.
• Use computers for producing tables and graphs and for making spreadsheet calculations.
• Troubleshoot common mechanical and electrical systems, checking for possible causes of malfunction, and decide on that basis whether to make a change or get advice from an expert before proceeding.

12D. Communication Skills

By the end of the 12th grade, students should be able to

• Make and interpret scale drawings.
• Write clear, step-by-step instructions for conducting investigations, operating something, or following a procedure.
• Choose appropriate summary statistics to describe group differences, always indicating the spread of the data as well as the data's central tendencies.
• Use and correctly interpret relational terms such as if . . . then. . . , and, or, sufficient, necessary, some, every, not, correlates with, and causes.
• Participate in group discussions on scientific topics by restating or summarizing accurately what others have said, asking for clarification or elaboration, and expressing alternative positions.
• Use tables, charts, and graphs in making arguments and claims in oral and written presentations.

12E. Critical-Response Skills

By the end of the 12th grade, students should be able to:

• Notice and criticize arguments based on the faulty, incomplete, or misleading use of numbers, such as in instances when (1) average results are reported, but not the amount of variation around the average, (2) a percentage or fraction is given, but not the total sample size (as in "9 out of 10 dentists recommend..."), (3) absolute and proportional quantities are mixed (as in "3,400 more robberies in our city last year, whereas other cities had an increase of less than 1%"), or (4) results are reported with overstated precision (as in representing 13 out of 19 students as 68.42%).
• Check graphs to see that they do not misrepresent results by using inappropriate scales or by failing to specify the axes clearly.
• Wonder how likely it is that some event of interest might have occurred just by chance.
• Insist that the critical assumptions behind any line of reasoning be made explicit so that the validity of the position being taken-whether one's own or that of others-can be judged.
• Be aware, when considering claims, that when people try to prove a point, they may select only the data that support it and ignore any that would contradict it.
• Suggest alternative ways of explaining data and criticize arguments in which data, explanations, or conclusions are represented as the only ones worth consideration, with no mention of other possibilities. Similarly, suggest alternative trade-offs in decisions and designs and criticize those in which major trade-offs are not acknowledged.

Materials Needed

Computers with Internet connections

Plastic Garbage Bags

Meter Sticks or Measuring Tapes for Measurement of Sampling Areas

Berlese funnels (either commercially purchased or homemade)

40 Watt Light Bulb (MAXIMUM wattage, 1 per funnel)

Beakers (400 ml minimum, 1 per pair of students)

95% ethanol (minimum of 200 mls. per pair of students)

Binocular Microscopes (1 per pair of students)

Binocular Microscope Light Source (gooseneck desk lamps recommended if the binocular microscopes lack internal light sources)

Plastic Petri Dishes (1 per pair of students)

Colored Construction Paper (1 package for all of your classes)

Special Requirements

As in past investigations involving Berlese funnels, teachers should be certain to use light bulbs with a maximum wattage value of 40 watts. Be certain to check each Berlese apparatus prior to the end of each class to determine that the light source is positioned in a stable manner and is a minimum of six inches from the top of the sample being extracted. These practices will eliminate fire potential.

Commentary on Subject Matter

Berlese extraction is an excellent ways for students to begin to understand the full range of organismal diversity around them. Since the samples are collected by the students, the activity is much more personal than the extraction of teacher-supplied samples. In addition to worms of various types, students will likely obtain large numbers of mites, springtails (collembola), centipedes, millipedes and beetles. Mites and collembola are typically the most abundant organisms extracted in soils and leaf litter throughout the world. An excellent source for additional information regarding Berlese extraction and the different types of arthropods encountered is Howard Evans' Life on Little Known Planet: A Biologist's View of Insects and Their World.

The quantitative analysis component serves as an excellent catalyst for discussion regarding faulty, incomplete, or misleading use of numbers, alternative ways of explaining data and criticizing arguments in which data, explanations, or conclusions are represented as the only ones worth consideration, with no mention of other possibilities. This activity meshes well with state and national standards for science, math and critical reasoning.

Commentary on Instructional Approach(es)

All of the components of this activity lend well to collaborative group work. The Internet and Proposal Writing components should be relatively straightforward. Components are set up such that the activity can be terminated at the end of either component A, B or C. However, the components are sequential and don't make sense unless the previous components are completed. Each of the components lends well to teacher modification.

Assessment

The Internet research component is probably best assessed by examining content and structure of student write-up of their findings and degree to which their write-up conforms to teacher-specified format. Guidelines for the write-up are presented in the student instructions. The same standards should be used for evaluating the proposal writing component of the activity. Again, guidelines for the write-up are presented in the student instructions. The final write-up of student-performed experiments should be evaluated based on final write-up information and format. Additionally, teachers may want to consider adding a culminating oral presentation to this set of activities.

Pertinent Online Resources

Compendium of Hexapod Classes and Orders (http://www.cals.ncsu.edu:8050/course/ent425/compendium/index.html)

Alphabetical and phylogenetic listing of commonly found arthropods (primarily insects). Teachers may want to review general information for many of these organisms prior to the activity.

Entomology for Educators (http://www.cals.ncsu.edu/course/ent591k/)

Online resources for a class, this resource contains numerous links to web pages dealing with different aspects of arthropod biology and impact of arthropods on people.

Sampling Design: Structured Inventory (http://www.eman-rese.ca/eman/ecotools/protocols/terrestrial/arthropods/sampling.html)

An excellent overview article dealing with the many factors that need to be kept in mind when designing a meaningful experiment (collecting techniques, replication, methodology, etc). Followup pages at this site deal with abiotic protocols, Berlese-Tullgren arthropod extraction from soil and litter, pitfall traps, and pan traps. Very highly recommended!!!