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The origin of cells and cell division 1.5 + 1.6

Planning sheet for the origin of cells and cell division

Desired Results

Understanding(s)

  • Cells can only be formed by division of pre-existing cells. (link to cell theory)
  • The first cells must have arisen from non-living material.
  • The origin of eukaryotic cells can be explained by the endosymbiotic theory.

    Endosymbiosis - Nature of Science

  • Mitosis is division of the nucleus into two genetically identical daughter nuclei.
  • Chromosomes condense by supercoiling during mitosis.
  • Cytokinesis occurs after mitosis and is different in plant and animal cells.

    Mitosis and the Cell Cycle

  • Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.(including G1, S, G2)
  • Cyclins are involved in the control of the cell cycle.
  • Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

    Control of cell cycle & cancer

Essential Question(s)

  • What is the role of cell division in the origin of life?
  • Where did the first cells come from
  • As well as dividing can cells join together?
  • What would happen if one cell engulfed another without killing it?
  • What are the stages in cell division by mitosis?
  • How do cells control the cell cycle?
  • What causes cell division to go wrong and become cancer?

ToK / NoS / IM

  • How can the principal that cells come from pre-existing cells be verified.
  • Reductionist approach - investigation of the component parts of living things
  • Systems approach - examination of whole organisms / systems.
  • How to decide between the different approaches?
  • Serendipity - discovering by accident, e.g. cyclins. Is this really luck, or intuition?
  • International nature of scientific research is exemplified by the worldwide effort to find causes and treatments for cancer in Oncology.

Skills students will have

  • Application: Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth.
  • Application: The correlation between smoking and incidence of cancers.
  • Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph.(prophase, metaphase, anaphase and telophase).
  • Skill: Determination of a mitotic index from a micrograph.

    Mitotic index & cancer

Assessment Evidence

Assessment Evidence including Performance Tasks, Self-Assessment and Reflection

Summary in Goal.Role.Audience.Situation.Performance.Success criteria.

Facets of understanding - Explain, Interpret, Apply, Perspective, Empathy, Self understanding.

Learning Activities

Mitosis and the Cell Cycle

Time: 1h Mitosis is a miraculous process. In the making of the three trillion cells of our bodies it manages to faithfully share the chromosomes equally between the daughter cells. This lesson focuses on the key details which help students achieve high marks in exams and the activities help students to make sense of these details in the context of the whole process of mitosis.

Endosymbiosis - Nature of Science

Time: 1h The idea that mitochondria once existed as free living bacteria and that a simple cell engulfed one of these bacterial cells and promptly became a eukaryote cell is a difficult idea to ‘prove’ but is a great illustration of the nature of science. This story of a biologist’s tenacity and ingenuity in her research over sixteen years illustrates some important ideas about the nature of science. Students read the webpages and answer the questions to gain an insight into endosymbiosis and the scientific method

Mitotic index & cancer

Time: 1h  In this activity students are first guided through the identification of cells in the different stages of mitosis. Following this, the next task is to count and record the number of cells undergoing mitosis and those which aren't in samples from human breast tissue biopsies. The calculation of the mitotic index is carried out and the results used as a prognostic tool to decide the nature of cells in the samples.

Control of cell cycle & cancer

Time: 1h The control of the cell cycle is essential for the normal functioning of the body. Cyclins have a key role in this control. Oncogenes have the opposite effect and effectively remove the control of the cell cycle and the cells divides to form a tumour. This activity introduces students to these concepts without getting too complicated.

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