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Comparative Anatomy Written Lab Bones
- 1. Chapter 33 Comparing Chordates Observing Vertebrate Skeletons Introduction The body plans of all vertebrates are similar in some ways. One characteristic shared by all vertebrates is the presence of a skeleton. The skeleton of a vertebrate is an endoskeleton, or internal skeleton. It is made up, in part, of living cells and thus is able to grow. It is not shed as are many exoskeletons. The endoskeleton provides support, protects the internal organs, and is a site for the attachment of muscles. Skeletal similarities are evidence that these different animals have evolved from a common ancestor. Structures such as bones that have a common origin but different function are called homologous structures. In this investigation, you will compare the skeletons of several different vertebrates and look for evidence of homologous structures. You will also classify unknown bone specimens. Problem What are the similarities and differences among vertebrate skeletons? What homologous structures can be identified on these skeletons? Pre-Lab Discussion Read the entire investigation. Then, work with a partner to answer the following questions. 1. What will you be comparing in this investigation? The skeletons of a human, a frog, a crocodile, a pigeon, a cat, and an unknown animal. 2. What do the animals you will be studying in this investigation all have in common? They are all vertebrates. 3. What evidence will you be looking for to demonstrate that vertebrates share a common ancestor? The presence of homologous structures 4. Based on the investigation title and the other animals you will be studying in this investigation, from what group of animals will the mystery bones come? The mystery bones are part of a vertebrate. 5. How will you determine which parts of the skeleton the mystery bones come from? By comparing them to the bones in the skeletons that are illustrated Biology Laboratory Manual B/Chapter 33 215 Name______________________________ Class__________________ Date ______________ ©Prentice-Hall,Inc. You may want to refer students to Section 33–3 in the textbook before performing this investigation. Time required: 45 minutes If actual skeletons or models are available, they should be used in conjunction with this investigation. Vertebrate skeletons can be obtained from a biological supply house.
- 2. Materials (per group) set of “mystery” bones Procedure 1. Carefully examine the labeled human skeleton in Figure 1. The human skeleton contains more than 200 bones. Become familiar with the names and structures of the bones in Figure 1. Human Skeleton 216 Biology Laboratory Manual B/Chapter 33 ©Prentice-Hall,Inc. Ribs Sternum Humerus Radius Ulna Carpals Metacarpals Phalanges Femur Patella Fibula Tibia Tarsals Metatarsals Phalanges Scapula Vertebrae PELVIC GIRDLE Ilium Cranium SKULL Maxilla Mandible Clavicle PECTORAL GIRDLE HAND FOOT Pubis Ischium Figure 1 The “mystery” bones can be made by boiling a chicken and removing the meat from the bones. For a more challenging problem, you can obtain pig, lamb, or cattle bones from a butcher or grocery store; cook the bones to destroy pathogens. Each group should be given several bones from the same type of animal to identify.
- 3. 2. Look at the frog skeleton in Figure 2. As you examine the skeleton, compare it to the human skeleton in Figure 1. Label the bones of the frog skeleton using the names from Figure 1. 3. Repeat step 2 with the skeletons of the crocodile, pigeon, and cat in Figures 3, 4, and 5. 4. Obtain a set of “mystery” bones from your teacher. Identify the bones by comparing them to the bones of each skeleton observed in this investigation. Wash your hands with soap and warm water before leaving the lab. Biology Laboratory Manual B/Chapter 33 217 Name______________________________ Class__________________ Date ______________ ©Prentice-Hall,Inc. Frog Skeleton Figure 2 Crocodile Skeleton Figure 3
- 4. 218 Biology Laboratory Manual B/Chapter 33 ©Prentice-Hall,Inc. Pigeon Skeleton Figure 4 Cat Skeleton Figure 5
- 5. Analysis and Conclusions 1.Comparing and Contrasting What are three characteristics that all of the skeletons share? Answers may include a bony skeleton, four limbs, a skull, presence of vertebrae in the backbone, jaws, and an internal skeleton. 2.Comparing and Contrasting What are three differences that exist among the skeletons? Answers may include number of bones, presence of a tail, shape of bones, overall size, and type of teeth. 3.Drawing Conclusions How do the functions of the forelimbs differ among the five vertebrates you have examined? The forelimbs of humans are used for grasping objects, the forelimbs of frogs are used in landing after a jump, the forelimbs of pigeons are used for flying, and the forelimbs of crocodiles and cats are used for walking. 4.Analyzing Data What type of evidence would indicate that the human hand, pigeon wing, and cat paw are homologous structures? These structures contain bones of similar shape, number, and arrangement. 5.Classifying Which of the skeletons is most closely related to the human skeleton? What evidence supports your answer? With the exception of the tail, the backbones of humans and cats are most alike in the number and arrangement of vertebrae. 6.Classifying To what type of animal do you think your “mystery” bones belong? On what evidence do you base your conclusion? Answers will depend on the unknown skeleton bones provided. If chicken bones are used, students may recognize the flat sternum and the fused metacarpals. 7.Drawing Conclusions Are bones that are similar in structure always similar in function? Give an example to defend your answer. No. While the forearms of cats and humans are similar in structure, the cat generally uses its forearms for walking, and the human uses its forearms for grasping objects. 8.Drawing Conclusions What evidence have you obtained in this investigation to support the theory that vertebrates evolved from a common ancestor? All of the vertebrates examined in this investigation had homologous structures within their skeletons. Biology Laboratory Manual B/Chapter 33 219 Name______________________________ Class__________________ Date ______________ ©Prentice-Hall,Inc.
- 6. 9.Comparing and Contrasting How do the bones in the limbs of the frog differ from those in the other four skeletons? The frog has only one bone in the forearm (radio-ulna) and one bone in the lower leg (tibia-fibula). 10.Observing Describe the “mystery” bones in your collection. Answers will depend on the bones provided. 11.Drawing Conclusions To what parts of the skeleton do your “mystery” bones belong? Answers will depend on the bones provided. Going Further Using reference materials, find examples of other vertebrate skeletons. How are these skeletons similar to and different from those you have studied in this investigation? How are the skeletons of these other vertebrates adapted to the environments in which they live? 220 Biology Laboratory Manual B/Chapter 33 ©Prentice-Hall,Inc.