This activity introduces toxicology through a simple concept map. It immediately immerses students into the science of toxicology through an authentic toxicology investigation. The lab examines the effects of ethanol on California Blackworms
Estimated Time of Activity
Two hours or 2 to 3 class periods
Students will be able do the following as a result of the activity:
- Begin to develop concept mapping, team work, safe animal handling, data recording, and critical thinking skills.
- Understand the concept of dose-response and the definition of toxicology as well as its connections to other sciences, the real world, and their own lives.
- Learn how to conduct a toxicological assay
Students should have a general understanding of chemistry and biology prior to beginning this unit. The unit is suitable for a chemistry, biology, or environmental science class.
- Introduce concept mapping by writing the term “toxicology” on the board and encouraging students to state or write words, phrases, or terms that come to mind when they hear the word toxicology.
- Develop the concept map with the class by recording student responses on the board (or designate a student recorder). Encourage students to make connections to themselves, their environment, and what they know about toxins and environments from other classes.
- Form the students into groups of 3 to 5 depending on class size and collect the materials needed for the Blackworm lab.
- Students should examine the blackworms and first distinguish the anterior end from the posterior end. The anterior is blunter and more darkly pigmented than the posterior. The anterior is also the end that will move first. If several worms are in the chamber, they will clump together in a ball, as they like to “cling” to things. This is a normal behavior that the students will want to note. Students can separate the group by gently probing the worms or pipetting with water.
- Once the anterior and posterior ends are established, students should begin observing the worms’ swimming behavior. Touch the probe to the posterior end. The worm will swim forward in a corkscrew fashion, alternating clockwise and counterclockwise. When the worm is probed on the anterior end, it will coil and reverse its position. Both these movements are quite rapid, and it may take some time for students to note the differences.
- Next, direct students to observe crawling behavior. The worm can be placed in a Petri dish or weighing dish on moistened filter paper (with all excess water removed). Again they should probe both the posterior and anterior ends of the worm. In each case the worm will move by peristaltic crawling (successive waves of muscle contractions) in the opposite direction.
- Have students record their observations in the data sheet provided in the Blackworm lab packet.
- Introduce the activity on pages 10-11 of the Blackworm packet and continue the lab as time permits.
Observe student participation with the group and class discussion. Review student Data sheets and their responses to questions 1-15 (pages 12-13) in the Blackworm lab packet.
The students should complete the observation data sheet in class as a group. Complete the lab and associated questions (1-15) over the next 2 classes. Discuss and answer the questions in groups. Remaining unanswered questions can be assigned for homework.
- Blackworm lab packet
- California Blackworms (available at aquarium/ pet stores where live fish food is sold)
- Ethanol (vodka)
- Graduated cylinders
- Four Petri dishes (top and bottom) per group
- Filter paper
- Probes (rubber bands, electrical tape, stir sticks)
- Beral pipettes
- Spring water
- Black permanent markers
- The concept mapping instructions were written for a classroom that is equipped with a standard chalkboard or white board. If your classroom is equipped with a smart board, you will have more sophisticated resources to develop the concept map and should use them accordingly.
- You will need to purchase California blackworms prior to class. These can usually be found at aquarium stores. Be sure to have adequate copies of the lab instructions from the Blackworm lab packet for the class (pages 10-11), and prepare the ethanol concentrations according to the lab instructor notes provided in the Blackworm lab packet (pages 2-3). It will save time if the teacher assembles the probes as well (page 4).