Introduction
This activity allows students to gain experience in extracting microarthropods from leaf litter using a Berlese Funnel and allows them opportunity to examine the specimens collected in this manner. Students will use Internet search engines to learn how Berlese funnels work, perform extractions using either homemade or commercial funnels, and classify several of their specimens using classroom resources. An optional activity allows students to develop their own Berlese funnels, which can be used in future years.
Grade Level of Participants
This activity works well with students in grades 6-12. Older students may be able to construct more complex funnels and will likely be able to use more complex resources such as dichotomous keys, often available in biology classrooms.
Duration Of Activity
2-3 days. This activity can be performed in two days if you opt not to have students build their own Berlese funnels.
Curriculum Connection
This activity integrates well into class coverage of topics including ecology, organismal diversity and field methodology. The extraction serves as an excellent activity prior to initial use of binocular microscopes and study of microscopy.
Linkage to National Science Standards - AAAS Benchmarks
The following AAAS Benchmarks are addressed through "Microarthropod Collection and Examination". Each of the knowledge or skill benchmarks below pertain 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.
By the end of the 12th grade, students should be able to
By the end of the 12th grade, students should be able to
Materials Needed
Special Requirements
Commercial Berlese funnels and required supplies can be purchased through commercial biological suppliers such as Carolina Biological Supply. Be certain to use light bulbs with a maximum wattage value of 40 watts, as well as 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.
Commentary on Instructional Approach(es)
The directions for this activity are straightforward and students enjoy the variety of different ways in which they work during this activity.
The first day's activities center around Internet search for information regarding different types of Berlese funnels. Berlese operation is relatively easy to understand, and students typically find the variations in funnel type to be fascinating. I suggest having each student sketch the variation of the Berlese funnel they find most interesting and then briefly discuss the role of each component of the funnel, as opposed to a fairly general statement of funnel function. This assignment can be turned in after completion or kept and handed in as part of a packet of assignments which is due upon completion of assigned arthropod activities.
Construction of funnels is fun and relatively simple. You may want to have students bring in gallon plastic milk jugs and have on hand the rest of the required supplies (hardware cloth, tin snips, gooseneck lamps, beakers and ethanol). Students with some knowledge of basic shop skills may bring supplies from home to make funnels similar to those available commercially. This activity will take most of the class period.
Extraction set-up takes about ten minutes once the funnels are ready. Students begin by pouring about 200 mls. of ethanol into the beaker, layer the material to be extracted on the hardware cloth, position the bulb a minimum of 6" above the leaf litter or soil, and turn on the lamp. Extraction is typically complete in about 24 hours.
Follow directions presented in the student handout. Encourage students to use texts and other resources to assist in identification. Consider having dichotomous keys available for student use. You may want to have students focus on this activity exclusively using classroom materials or may want to move directly to the next activity, Microarthropod Variation and Taxonomy, a classification activity which uses online classification resources.
Assessment
Assessment of the components comprising "Microarthropod Collection and Examination" can take a number of forms.
Degree of participation in and understanding of the first day's activities can be assessed by examining each student's Berlese funnel sketch and written presentation of the role of each of the components making up the funnel. As stated above, that assignment can be turned in immediately after sketch completion or handed in as part of a packet of assignments due upon completion of the assigned arthropod activities.
Teachers opting to have students make their own funnels (Day 2) may choose to assess student understanding by evaluating each student's funnel relative to their sketches from the previous day. Alternately, teachers may have students briefly show the rest of the class their funnel and discuss why they opted to construct it in the manner they chose.
Day 3 activities consist largely of microscopic examination
of specimens extracted from each sample as well as sketching and
labeling key characteristics used in the classification of each
organism. Day 3 activity assessment should center around sketch
detail and accuracy, labeling of diagnostic characteristics and
rationale for each student's classifications.
Pertinent Online Resources
Berlese Extraction (http://www.cals.ncsu.edu/course/ent591k/berlese0.html)
Berlese Funnel Technique (http://www.albany.edu/natweb/berlese.html)
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/)
Sifting, Separating and Extracting (http://www.inhs.uiuc.edu/cwe/wwwtest/collect/HTML/d16.html)
Make a Berelese Funnel (http://www.archbold-station.org/discoveringflscrub/unit3/unit3b1part2.html)