Lesson 1 consists of one activity that engages students in the study of bones, muscle, and skin. Through a teacher demonstration and class discussion, students share their prior knowledge about living systems and bone, muscle, and skin. Students then develop a list of characteristics of living things and their own understanding of bone, muscle, and skin as living systems.
Bone, muscle, and skin are living systems. Some common characteristics of living systems are that they
After completing this lesson, students will be able to
See the following sections in Information about the Musculoskeletal and Skin Systems:
|1||No||Master 1.1, It’s Alive! Or Is It?, 1 copy per student||1 piece of white chalk
1 rubber band
1 piece of heavy paper, wrapping paper, or a report cover
1 chicken breast bone, “wishbone,” or other animal bone that is dried and easily broken
1 piece of raw meat of any kind, although red meat may be more easily associated with muscle
1 piece of chicken skin
1 pair of scissors
Wash the chicken bone, raw meat, and chicken skin. Keep the meat and skin on ice prior to use. Wear plastic or rubber gloves when handling these items to prevent possible bacterial contamination. Cover an area of a front table or workbench with nonabsorbent material to prevent contamination of the work space. Have necessary materials on hand to dispose of meat and chicken skin in accordance with your school’s regulations. Just before class, pair the materials as follows: chalk with bone; rubber band with muscle; and paper with skin.
Note to teachers: In this lesson, students develop a list of characteristics of living systems. Defining life is not a trivial task. Life has been defined in many ways for many different purposes, and there is no single definition that works for everyone. The characteristics that we focus on in this lesson were derived with the following in mind:
Proceed through the lesson at a steady pace. The idea is to elicit students’ prior knowledge about living systems and help them appreciate that muscle, skin, and especially bone contain living cells.
Allow only two to three minutes to develop this list. Student responses will vary. They may indicate that both skin and paper are flat and flexible. In addition to observable characteristics, try to focus students on functions. Both items can be used as coverings to contain things or as a protective layer for items beneath them.
Note to teachers: Asking this question requires students to call on their prior knowledge and to engage their thinking. At this point, do not critique student responses. Appropriate teacher comments are short and positive, such as “Good” and “What else?” Other appropriate teacher responses include “Why do you believe that?” or “How do you know that?” Questions such as these allow you to assess current student knowledge about the subject and adjust lessons accordingly. They also provide a springboard to “Let’s find out” or “Let’s investigate.” In general, it is time to move forward when you see that thinking has been engaged.
Once again, allow only two to three minutes to develop this list. Student responses again will vary. Although they probably will lack details, they may indicate that paper and skin are made of different things. Try to get students to elaborate on this response. They may also indicate that both came from sources that were alive at one time.
Developing lists of similarities and dissimilarities for these two pairs should proceed quickly. For each pair, try to have students come up with at least one response relating to what each item is composed of. Note that it is possible that students may not know that meat is animal muscle. If necessary, tell them that meat is muscle tissue.
Students will realize that the chalk, rubber band, and paper cannot repair themselves. They also should realize that the bone, meat, and skin cannot repair themselves. Some students, however, may make the leap to bone, muscle, and skin in an intact organism, such as a human, and indicate that these three systems can indeed repair themselves.
All students should lower their hands unless their injury is very recent or they have a condition that prevents normal healing. Some students may indicate that healing occurred, but it took a long time. All student responses are appropriate for discussions later in this lesson and in subsequent lessons.
Note to teachers: Some students may raise the issue of scars forming at the site of a previous skin injury. Rather than allow this topic to change the focus of class discussion, simply indicate that scar formation is an indication that the tissue has healed.
While students may understand that there are basic differences between muscle in their body and meat on the table, for instance, they may have trouble expressing what those differences are and why the two function differently. You may have to guide the discussion by asking additional questions:
Try to guide this brief discussion so that students view the bone, muscle, and skin of their bodies as active, changing, and responsive systems that are connected to other body systems, such as nerves and blood vessels.
Give teams just five minutes for this task. If students need help getting started, suggest that they think about finishing sentences that begin, “Living systems are made of …” or “Living systems are able to ….”
Write the responses on the board. Try to summarize the responses like this: living systems
If students respond that living systems can move, for instance, you might indicate that this characteristic is the result of obtaining and making energy and interacting with the environment.
Note to teachers: The ability to reproduce is a commonly listed characteristic of living systems. In this lesson, that characteristic is not listed separately because bone, although it is a living system, does not reproduce itself. Rather, the cells of bone reproduce and carry out those activities (such as making protein and depositing mineral) that allow bone to grow, repair, and remodel itself. If students mention reproduction as a characteristic of living systems, list this response under “function according to a genetic blueprint (the cells contain DNA).”
Why bone, muscle, and skin have been grouped for this module may not be obvious to students. Answering this question provides an opportunity for students to reflect on prior knowledge, and it sets the stage for the investigations to follow. Over the course of this module, students will develop the understanding that these systems all have structural functions and they protect the body. Also, these systems simultaneously allow flexibility and strength.
|Activity 1: It’s Alive! Or Is It?|
|What the Teacher Does||Procedure Reference|
Focus students’ attention on the three pairs of materials: paper and skin, chalk and bone, and rubber band and muscle.
Ask how each pair differs:
|Steps 2 and 3|
Break the chalk and bone. Cut the rubber band and meat. Cut the paper and chicken skin.
Ask students to raise their hands if they have ever broken a bone, injured a muscle or cut their skin.
|Steps 5 and 6|
Ask students why their bones, muscle, and skin can heal but the samples on the table cannot.
Divide the class into teams of three or four. Instruct teams to
|Steps 8 and 9|
Give each student a copy of Master 1.1, It’s Alive! Or Is It?
|Steps 10 and 11|
Ask students whether they believe that bone, muscle, and skin are living systems.
|Steps 12 and 13|
Ask students to write an answer to the question at the bottom of Master 1.1, It’s Alive! Or Is It?
|Steps 14 and 15|
Explain that they will now investigate bone, muscle, and skin.
|= Involves copying a master.|