Processes of cell division both maintain continuity and allow for diversity. Essential questions that drive this unit include:
a. What is the difference between growing and reproducing?
b. How can a mother produce egg cells (or a father produce sperm cells) which differ from each other when the parent's cells all have the same genetic makeup?
c. How can humans be so much alike and yet so different?
Reside at the heart of the discipline
The concepts of continuity and change in species are central to biological science. In order to understand this concept, students need to understand the role of the distribution of chromosomes in both mitosis (maintaining genetic continuity within an organism) and meiosis (providing recombination opportunities and diversity in offspring). Once students understand the role of each process in a species' life cycle, they have the understandings necessary to proceed into genetics concepts.
Represents a big idea having enduring value beyond the classroom: With the foundational understanding of the role of meiosis in genetic diversity, students can build an understanding of basic human genetics and its role in their lives.
Require uncoverage (the identification and clarification of misconceptions): Meiosis is a very abstract concept for students and requires uncoverage to eliminate misconceptions. Only until the abstract process of meiosis is made more concrete, will students understand the cellular level of genetics.
Offer potential for engaging students: Because this process and the previously covered process of mitosis relate to the human reproductive cycle, they relate to the students' lives. The connection to current technologies and increasing knowledge in genetics makes it even more engaging.
a. Informal checks on understanding throughout the unit (exit cards, question box, concept mapping, oral questioning and follow-up probes)
b. End of unit performance assessment that demonstrates understanding of the mitotic process (choice of physical role-play modeling, written analogy, cell stories, or computer based products)
c. Computer driven self-quiz on meiosis and its contrast to mitosis
d. Work with a partner to develop a product that communicates the major differences between mitosis and meiosis and their roles in the reproductive cycle (choice of means of communication - graphic, musical, etc).
e. Self-assessment and peer-assessment of understanding (using computer software and quizzes at internet web sites
a. Crack the Code: Rather than a teacher-directed assignment of vocabulary, this introductory lesson is a student-centered exploration of the terms encountered in this unit and the following genetics units. This small-group, problem-solving activity models the way in which scientists are making discoveries about the Human Genome. This activity will introduce some of the language of cell division and genetics, as well as model the concepts of coding, pairing, combining, and expressing. The vocabulary will be a resource, with posters hung around the room for student reference. It ends with student reflection to determine what students want to know about genetics.
b. Meiosis Role-play: Students are not expected to learn the phases of meiosis in this activity, but instead to understand the underlying concepts and how the process provides diversity (meiosis). Students will also be introduced to the role of the process in the human reproductive cycle, with a discussion of the varying roles of mitosis (connecting to students' past understandings) and meiosis. This full class role-play allows for successful command of information by spatial and bodily/kinesthetic learners, rather than depending upon lecture/note-taking, which limits knowledge access to linguistic learners.
c. Understandings of Meiosis: A More Detailed Picture: Once students have an understanding of the basic purpose of meiosis, an overview of the process, and the importance of independent assortment, they move on to this activity which steps them concretely through the stages of meiosis. A variety of options for concrete experiences are provided including computer simulations, pop bead or pipe cleaner modeling, and NIH imaging to understand the connection to meiotic divisions to genetic diversity. Extension components (optional) are included which explore the stages in more detail and provide an exploration of associated vocabulary.
d. Meiosis Misconception Cartoons: This lesson has pairs of students develop cartoons or other graphic representations that portray the differences between major terms which are often confused: allele and gene; chromatid and chromatin; tetrad and two pairs of chromatids; chromatid and chromosome; centriole and centromere; replicating, duplicating and splitting (as the terms apply to chromosomes); synapsis and the pairing off of chromosomes. Some of these are essential pairs; others are given as extension activities.
e. Concept connections: This lesson encourages students to make connections between these unit and previous learning (cell growth and division). It has students develop concept maps which compare and contrast their current understandings of mitosis and meiosis. Connections to the reproductive cycle will be included.
f. Cell Division Extension: Students may opt to test their understandings of mitosis and meiosis at an interactive web site:
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