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NESTED STUCTURE 3
TITLE: Normal vs. Abnormal Cell Division
INTRODUCTION: This lesson is used to get students interested in the next nested structure. This lesson ties together everything that the students have covered thus far in this unit. Students have learned that cancer is abnormal cell growth, students know that cancer cells abnormally divide, and they should understand the process of normal cell division. This lesson intrigues students to hypothesize why cells lose their ability to control cell division. It should create a small scientific community within the classroom in which students feel free to create a hypothesis and discuss their ideas with their peers. For homework, students will start to research to topic of uncontrolled cell division and compare it to their original hypothesis.
OBJECTIVES: • Students will be able to describe the process of normal cell division including the cell structures involved at each stage and the reason they are present. • Students will be able to discuss as a class what happens if the involved organelles fail or part of mitosis is incomplete. • Students will be able to understand that mitosis is a controlled/regulated process. • Students will be able to hypothesize why cells divide abnormally. • Students will be able to criticize other peers hypothesis about abnormal cell division.
STUDENTS PRECONCEPTIONS: Students hold many preconceptions about the topic of cancer and cell division. Many students understand that cancer is a disease. A common preconception (misconception) that students hold is that cancer is a virus. Many students were also unable to relate the process of abnormal cell division to cancer. Lastly, and most relevant to this lesson, nearly all students were unable to describe why cancer cells divided abnormally. Some students gave responses such as “the sun fried the cells thus making them bad cells”. This lesson should hopefully clear up some misunderstanding. It should help students understand that abnormal cell division is loss of control in mitosis.
MATERIALS: 1. chalk board/ white board 2. colored chalk/ colored markers 3. copies of Diagram 1 for the entire class
PREPARATION: The teacher should make enough copies of diagram 1 for each student in the class. The teacher should also review all questions and that will be asked in the group discussion and be prepared if the students go off track. Also, as with the previous lesson, the instructor should review the mitosis cell division cycle and stages so that he or she can accurately correct inaccuracies in the students drawings on the board. There a mitosis information sheet provided in the previous lesson.
TIME: 30 minutes
ACTIVITIES: • The teacher should open the class up by reminding the class what they had learned last class about normal cell division. He/she should break the class up into 7 groups and compare their homework assignments. Each group will be given one of the following categories: o Interphase o Prophase o Prometaphase o Metaphase o Anaphase o Telophase o Cytokinesis • Each group is responsible for drawing their stage on the board. The stages should be discussed as review of the previous class. Once the stages have been covered, the teacjer should open a class discussion. The teacher should use the drawn diagrams to help ask the following questions: o Are these all of these organelles, chromosomes, centrioles, spindle fibers, etc., necessary for cell division? o What happens if the spindle fibers do not form in prophase? o What happens if all chromosomes do not divide and one daughter cell is left with no DNA? o Will the cell still under go cell division? • Remind the class they have already learned that tumors (a source of cancer) are caused by abnormal cell division. Provide each student in the class with a copy of Diagram 1 provided in the back of the lesson plan. Ask the class this next set of questions: o You have already learned that cancer is abnormal cell division. In what ways are the cancer cells abnormal? o Are they larger than normal cells? o What makes them different? o Are they more numerous? The teacher should not need to ask all of these questions. They are just a guideline to be used if the class gets stuck or does not seem to be going in the right direction. • Once the class has discovered that cancer is the uncontrolled growth of cells, the next set of questions is used to get the students interested in the next nested structure. Have the students in pairs set up hypothesis as to what they think are the answers to these questions. Inform the students that everyday scientists come across questions that they do not know and that they form a hypothesis and then try to study and test them considering there is never a right answer in NOS. o Cells are very controlled. They always grow and divide in the precise process of mitosis. How would cells divide abnormally? o What might happen in abnormal cell division? o Why would a cell divide abnormally? • As a class discuss the different hypothesis that the class came up with. Students may mention outside forces altering the time between divisions. There are an unlimited amount of possible answers the students may create. For homework, the teacher should tell the students to ask parents, friends, or the internet what causes abnormal cell division. The paragraph should describe their findings and do a comparison to their original hypothesis. Tell them to write a one paragraph response to be collected the next day in class. • Here are a list of possible websites the students can use: http://cancerquest.org/index.cfm?page=262 http://www.biologyreference.com/Bl-Ce/Cell-Cycle.html http://training.seer.cancer.gov/module_cancer_disease/unit2_whatscancer3_cell_biology.html
ASSESSMENT: The teacher will be able to observe the students in the class discussion and can assess how well they understand the material being presented. The instructor will vary his or her questions according the level of understanding the students achieve after each question. The second assessment will be the homework assignment the students are given at the end of the lesson. It will be collected the following class period. The instructor should assess the students on their individual hypothesis and well as the ability to arrive at an explanation to their hypothesis.