On the Cutting Edge: Rat Dissection External Exam

If you are considering doing (or currently do) a rat dissection with your students, don’t forget to include a comparative anatomy element to the lab. The rat’s body structure and organ systems are relatively similar to those of a human. This similarity provides an interesting look into mammalian anatomy and allows students to make comparisons between humans, rats, and other mammals. Before your students start cutting, have them study the external anatomy to garner clues about the organism’s habitat and behavior, and how humans compare.

Content standards

National Science Education Standards
This activity is appropriate for middle and high school students and addresses the following content standards:

• Grades 5–8: Life Science: Structure and Function in Living Systems; Regulation and Behavior; Diversity and Adaptations of Organisms
• Grades 9–12: Science as Inquiry: Abilities Necessary to Do Scientific Inquiry
• Grades 9–12: Life Science: Matter, Energy, and Organization in Living Systems; Behavior of Organisms

AP® Biology course topics

• Organisms and Populations: Diversity of Organisms; Structure and Function of Plants and Animals

Before you start

Students are often eager to start cutting and forget about observing the external features of the organisms they are dissecting. Take time to help them explore the external anatomy. There are many clues to an organism’s habitat that students can find by studying the external features. Preceding your rat dissection activity, generate class discussion by using some of the questions listed below. Answers will vary depending on students’ prior knowledge of rodent characteristics and anatomy.

Pre-dissection questions

1. Where do rats live?
2. What do rats eat?
3. Do rats bear live young?
4. List at least 3 ways in which rats are similar to humans.
5. Describe a rat’s foot structure and for what it might be useful.

Materials

• Carolina Rat Dissection BioKit®
• Dissection Tray
• Pair of Disposable Gloves
• Safety Glasses
• Dissecting Instruments (Intermediate Dissecting Set 1)

Figure 1. Rat external anatomy.

Procedure

1. Review Figure 1 and position it where you can refer to it during the activity.
2. Place the specimen on a dissecting tray and observe the external anatomy of the rat. Note: Double-injected specimen may exhibit blue and/or red pigment in the 2 areas where skin was cut away. This coloring is from latex injected into the vascular system to allow simplified identification of the specimen’s veins and arteries.
3. Examine the rat, observing it from all angles.
4. Manipulate your specimen’s limbs and note the organism’s articulation.
5. Open the mouth and observe the rat’s dentition.
6. Try to locate the following structures:
1. Head
1. Nares¹
2. Ear (pinna)
3. Whiskers (vibrissae)
4. Eyes, each with remnant of nictitating membrane (plica semilunaris)
2. Female structures and openings
1. Urethral orifice¹
2. Vagina¹
3. Anus¹
3. Male structures and openings
1. Urogenital opening¹
2. Anus¹
3. Scrotum¹
4. Feet
1. Claws
2. Foot Pads

Extend

Use the students’ findings from this external examination to support or reject the answers to the questions above. Allow the students to justify their answers in an open class discussion. This activity is an excellent way to help enhance observational and reasoning skills.

Now your students are ready to learn about the rat’s internal anatomy—and Carolina’s Rat Dissection BioKit® is a great resource to teach the anatomy of this specimen. The complete kit includes 15 double-injected Carolina's Perfect Solution® white rats, plus a detailed teacher’s manual with dissection instructions, extension activities, reproducible student sheets, background information, glossary of terms, and dissection questions for discussion.

1. Item labeled on Figure 1.

AP® Biology is a registered trademark of the College Board®, which was not involved in the production of, and does not endorse, these products.