Observing Vertebrate Skeletons

Transcription

1 Name Class Date Chapter 33 Comparing Chordates Observing Vertebrate Skeletons Introduction One characteristic common to all vertebrates is the presence of a skeleton. The endoskeleton provides support, protects the internal organs, and is a site for the attachment of muscles. In jawless fishes lampreys and hagfishes and in sharks and rays, the endoskeleton is made of cartilage. Other vertebrates have endoskeletons of bone with small amounts of cartilage present. Similar skeletal features reveal important evolutionary links among vertebrates. 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 based on their similarities to and differences from known vertebrates. Problem What homologous structures can be identified in vertebrate 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. You may want to refer students to Section 33 3 in the textbook before performing this investigation. Time required: 45 minutes 2. Which labels on the human skeleton show specific groups of bones? Skull, pectoral girdle, pelvic girdle, hand, and foot are all groups of bones. 3. How will you label the bones in Figure 3? By finding a corresponding bone on the human skeleton and noting the name. 4. How will you begin to identify your mystery bones? Note the general size and shape, then compare it to the different skeletons. 5. Are you certain that your mystery bones will be from an animal whose skeleton is pictured in this lab? No, the bones may be from a completely different animal. Biology Laboratory Manual A/Chapter

2 Materials (per group) set of mystery bones If actual skeletons or models are available, they should be used in conjunction with this investigation. 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 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. any pathogens. Each group should be given several bones from the same type of animal to identify. Cranium Vertebrae Maxilla Mandible Clavicle Scapula Sternum Ribs SKULL PECTORAL GIRDLE Humerus Radius PELVIC GIRDLE Ilium Pubis Ischium Ulna Carpals Metacarpals Phalanges HAND Femur Patella Fibula Tibia Tarsals Metatarsals Phalanges FOOT Human Skeleton Figure Biology Laboratory Manual A/Chapter 33

3 Name Class Date 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 Repeat step 2 with the skeletons of the crocodile, pigeon, and cat in Figures 3, 4, and 5. Figure 2 Frog Skeleton Figure 3 Crocodile Skeleton PHBIO LMA C33 F03 Biology Laboratory Manual A/Chapter

4 Pigeon Skeleton Figure 4 Cat Skeleton Figure Biology Laboratory Manual A/Chapter 33

5 Name Class Date 4. Obtain a set of mystery bones from your teacher. Try to identify the bones by comparing them to the bones of each skeleton observed in this investigation. 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. Comparing and Contrasting How are the vertebral columns of the skeletons similar? How are they different? All of the skeletons have vertebral columns that consist of a series of individual vertebrae in a chain. The vertebral columns have different numbers and sizes of vertebrae. 4. Comparing and Contrasting How are the hindlimbs similar? How are they different? Each of the skeletons has one bone (femur) in the upper portion of the leg. Each of the skeletons has a different number of bones in the lower portion of the leg, the ankle, and the foot. 5. Comparing and Contrasting How do the foot bones of the frog, the crocodile, and the cat differ from one another? The frog has long feet for swimming; the cat has elongated metatarsals and claws; the crocodile has a relatively small foot. 6. Observing Describe the mystery bones in your collection. Answers should mention the sizes and shapes of the bones. 7. Classifying To what parts of the skeleton do your mystery bones belong? Answers will depend on the materials provided. Biology Laboratory Manual A/Chapter

6 8. Inferring 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. 9. Analyzing Data What type of evidence indicates that the human hand, pigeon wing, and cat paw are homologous structures? These structures contain bones of similar shape, number, and arrangement. 10. Drawing Conclusions To what type of animal do you think your mystery bones belong? On what evidence do you base your conclusion? Answers will vary according to the set of bones examined by the students. 11. 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. 12. 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. 13. Drawing Conclusions Which of the skeletons is most closely related to humans? What evidence supports your answer? The cat is most closely related to humans. Both are mammals, both have similar vertebral columns, both have similar forearms and hindlimbs, and the human hand is similar to the cat s paw. 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? 242 Biology Laboratory Manual A/Chapter 33