Students will be responsible for answering the following pre-lab questions:
1) Describe an open circulatory system. What organisms have open circulatory systems?
2) Describe a closed circulatory system. What organisms have closed circulatory systems?
3) What is the purpose of the Perch Dissection Activity?
4) Draw and label the external anatomy of the perch.
5) Label the internal anatomy of the perch on the diagram provided.
6) Outline the dissection procedure to examine the internal anatomy of the perch.
Prior to the start of class, the teacher will ensure that there are enough dissection trays with tools and perch. On hand will be latex gloves, two garbage bags, cleaning cloths/paper towels and washing basins/sinks with soap and water, first aid kit. (In terms of safety issues, this lab is quite safe. Students may accidentally cut themselves with the dissection tools so a first aid kit is necessary. No glass apparatus is being used. No chemicals are involved.)
At the beginning of class, the teacher will collect the pre-lab questions. Anyone who has not completed them will be asked to do so at that time.
The teacher will review the dissection procedure and students will be asked to make note of any instructions not explained in the text. For clean-up, the students will be asked to throw all body parts into the garbage bags. The dissection trays and tools must be washed in the basins /sinks and dried and placed where they were first found. The teacher will encourage all students to take a turn at dissecting. Also, depending on the group of students, the teacher may want to remark on acceptable behaviour during the lab to avoid a situation where students start playing catch with perch body parts.
Students will be instructed to work in pairs/small groups. One person from each group will pick up a dissection kit. One person from each group will pick up enough pairs of gloves for their group. When a group is at their lab bench, gloves on, dissection tray and apparatus in front of them, a textbook to follow along in and the sheet with additional instructions, the
teacher will give them a perch.
During the course of the dissection the teacher will supervise and ensure that students are contributing equally to the activity. Students will be required to draw and label a diagram of the internal anatomy of the perch as they see it.
At the end of the period, students will not be dismissed until all the garbage has been thrown out, the apparatus washed, dried and placed where it was found and all the lab benches are clean.
The students will be expected to hand in a lab write-up (excluding a hypothesis), their perch diagram and answers to the discussion questions.
Post-Lab Discussion Questions:
1. What evidence is there of a rich blood supply in the gills? Why is this rich blood supply important?
2. Is the perch’s circulatory system open or closed? Support your answer by describing what you observed.
3. What evidence is there that the perch’s circulatory system is linked to the systems for digestion and gas exchange?
4. What systems did you observe in the perch that help maintain the perch’s internal environment?
5. If a perch had a damaged swim bladder that could hold no air, would the fish sink to the bottom or float? Explain.