Gordon Reese
Product Manager, Preserved Materials and Prepared Slides

Comparative anatomy is an excellent approach to study the diversity of animal adaptations. Members of Kingdom Animalia have a variety of physical traits that enable them to survive in a wide range of environments, from the dark depths of the Pacific Ocean to the hot sands of the Sahara Desert. Students can examine the special adaptations that enable animals to survive in a particular environment by performing an inquiry-based dissection activity, such as the one presented in this article. This activity is appropriate for middle school and high school students. You can easily modify the procedure and the selection of species of study to meet your classroom needs.

In this activity, students study the hydra, sea star, earthworm, perch, and frog. Data tables include space to record information about the pig, mentioned in the "Extension activities" section below. Each of these species represents a member of Kingdom Animalia with various adaptations. Students first observe the external anatomy of the organisms and answer questions about their observations, then complete dissections of the organisms and compare the body systems.

Safety

Have students wear safety glasses or goggles, gloves, and lab aprons when dissecting.

Suggested materials

• Hydra Microscope Slides
• Preserved Starfish
• Preserved Earthworms
• Preserved Perch
• Preserved Frogs
• Preserved Pigs
• Adjustable Safety Glasses
• Laboratory Aprons
• Nitrile Disposable Gloves
• Aluminum Pans with Vinyl Dissecting Pad
• Student Dissecting Sets
• Copies of the Explore Animal Diversity with Inquiry-Based Dissection Student Guide
• Microscopes

Student procedures

1. Observe
   Before you dissect the organisms, observe the external features of each of the specimens. Ask yourself the following questions, and fill in the Data Table of Animal External Anatomy with your observations.

1. Examine the outer tissue of the animal. Is the animal exposed to the environment, or is the tissue modified to provide a covering?

1. Run your hand over the surface of the animal and describe the characteristics of the tissue. Is it hard or soft? How would you describe the texture? How would this type of tissue help the animal in its environment?
2. If the animal’s tissue is covered, how would you describe the covering? What purposes might the covering serve?

2. What is the predominant color of the organism? Is the animal more than 1 color? If so, describe the location of the different colors. Brainstorm various reasons that an organism might have these colorations.
3. Examine the teeth. Describe the shape/s of the teeth (dentition). Based on the dentition, is the animal an herbivore, carnivore, or omnivore?
4. Does the animal have structures that could be used to capture prey or defend itself? Describe these structures and their function.
5. Does the animal have eyes? If so, where are they placed on the head? List 2 different placements of the eyes and describe situations in which each placement would be advantageous. Why would organisms not have eyes?
6. Examine the body organization. Does the animal have radial or bilateral symmetry, or is it asymmetrical? Are there differentiated body parts (for example, head and tail)? If so, attempt to name each body part.
7. Does your organism have appendages? If so, how many appendages? What is the organism’s primary mode of locomotion?

Sample Data Table of Animal External Anatomy

External Characteristics	Hydra	Starfish	Earthworm	Perch	Frog	Pig
Modifications of outer tissue	No covering, jelly-like tissue	Spiny, hard shell	Segmented, smooth tissue; specialized enlarged area for reproduction without segmentation	Scales and bony fins	Smooth	Body covered in short hair, whiskers
Color/s and markings	Colorless/white	Dorsal side is darker than ventral side	Dark pink/red/brown	Yellow striped, dorsal side is darker than ventral side	Spotted, dorsal side is darker than ventral side	Pink
Dentition	None	None	None	Many sharp teeth	Small teeth in upper and lower jaws	Teeth not well developed
Defense	Stinging nematocysts	None	None	Spines on dorsal fin	Mucus glands in skin	None
Eyes	None	Spines	None	1 on either side of head	1 on either side of head	1 on either side of head
Symmetry	Radial	Radial	Bilateral	Bilateral	Bilateral	Bilateral
Appendages	None	5	None	Paired pelvic and pectoral fins, caudal fin, dorsal fins, anal fin, caudal fin	4: 2 forelimbs and 2 longer and larger hind limbs; webbed feet	4: 2 forelimbs and 2 larger hind limbs; hoofed feet
Mode of locomotion	Sessile	Water-vascular system (tube feet) to crawl across surfaces on ocean floor	Contraction and relaxation of setae to propel through soil	Muscle contractions of body and movement of fins to propel and direct through water	Use legs to jump, swim, climb, walk, and burrow	Use legs to walk, run, dig, and climb

2. Dissect
   Now carefully dissect each specimen. As you dissect each organism, answer the following questions and fill out the Data Table of Animal External Anatomy.
1. How does the animal exchange oxygen and carbon dioxide with the environment? Does the animal have respiratory structures (for example, lungs/gills)? How do the respiratory structures differ with the environment the animal lives in?
2. How are nutrients and gases transported through the animal to various tissues? Is the circulatory system closed and blood contained in veins/arteries, or open? Does the animal have a heart? If so, how many chambers are in the heart?
3. How does the organism break down foodstuffs into usable nutrients? Does the organism have a stomach, intestine, glands?
4. Does the organism have bones? If so, does the organism have vertebrae (backbone)?
5. Does the organism have a central nervous system (brain)?

Sample Data Table of Animal Internal Anatomy

Internal Anatomy	Hydra	Starfish	Earthworm	Perch	Frog	Pig
Respiratory system	Diffusion of gases	Diffusion of gases aided by tube feet	Diffusion of gases	Gills, covered with operculum	Lungs	Lungs with alveoli, diaphragm
Circulatory system	Nutrients diffuse throughout body	Network of fluid-filled canals that aid in nutrient transport; no heart	Closed, aortic arches, dorsal and ventral blood vessels; no heart	Closed, 2-chambered heart (atrium and ventricle), system of arteries and veins, 4 pairs aortic arches	Closed, 3-chambered heart (2 atria, 1 ventricle), arteries and veins	Closed, 4-chambered heart (2 atria, 2 ventricles), arteries and veins
Digestive system	Mouth and gastrovascular cavity	Mouth, stomach, intestine, anus	Mouth, pharynx, esophagus, crop, intestine, gizzard, anus	Mouth, esophagus, stomach, pyloric caeca, pancreas, spleen, gall bladder, liver, small intestine, anus	Mouth, esophagus, stomach, pancreas, liver, gall bladder, small intestine, large intestine, cloaca	Mouth, esophagus, stomach, liver, gall bladder, pancreas, small intestine, large intestine, cecum, anus
Skeletal system	None	None, calcified exoskeleton	None	Vertebrae, calcified bones and bony fins	Vertebrae and ribs, bony skeletons	Vertebrate, bony skeletons
Nervous system	Nerve net	Nerve net, nerve ring, and radial nerve	Ventral nerve cord	Brain (forebrain, midbrain, hindbrain), spinal cord, nerves	Brain with 10 pairs of cranial nerves	Brain with 12 pairs of cranial nerves

Extension activities

• If you do not have the animals above available, you can use other species. Consider adding the dogfish (a cartilaginous fish), grasshopper or crayfish (arthropod), or cat (mammal) to the study.
• Have students research the unique structures they discover during the dissections. For example, have students research and examine the features of the sea star’s water-vascular system, the earthworm’s circulatory system, the perch’s respiratory system, the frog’s excretory system (kidneys), and the pig’s reproductive system.
• Have students research the dentition of mammals to learn how different teeth are adapted to different food types. Have students present on the differences of heterodont and homodont, as well as the names for each type of tooth and the feeding type that corresponds to each.
• Have students pick a species and write a life cycle report on it.
• Have students compare human systems to those that they studied. Compare symmetry, respiratory system, circulatory system, and locomotion.

Related resources

Carolina has many kits that will aid you and your students in a study of animal diversity through dissection. The Comparative Animal Dissection Kit examines 9 animals from different groups. In addition to the animals described in this study (with the exception of the pig), the kit includes sycon sponges, mussels, crayfish, and grasshoppers with enough materials for a class of 24 students working in pairs.

For an advanced look at animal diversity and evolutionary relationships, the Animal Diversity Set for AP* Biology contains 13 representative organisms from the animal kingdom, along with instructions to perform dissections.

The Studying Classification with Cladograms Kit provides students with practice in classifying animals according to their morphological traits and making cladograms to visualize these relationships.

 

*AP is a registered trademark of the College Board, which was not involved in the production of, and does not endorse, this product.