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Cell Growth, Division, and Reproduction

Cell Growth, Division, and Reproduction. Learning Objectives. Explain the problems that growth causes for cells. Compare asexual and sexual reproduction. Warm up 12/9. Define these words Cell division Asexual reproduction Sexual reproduction. Limits to Cell Size.

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Cell Growth, Division, and Reproduction

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  1. Cell Growth, Division, and Reproduction

  2. Learning Objectives • Explain the problems that growth causes for cells. • Compare asexual and sexual reproduction.

  3. Warm up 12/9 • Define these words • Cell division • Asexual reproduction • Sexual reproduction

  4. Limits to Cell Size Why do cells divide rather than grow? The larger a cell becomes, the more demanding the cell places on its DNA. A larger cell is less efficient in moving nutrients and waste materials across the cell membrane

  5. A Visual Analogy Information overload Traffic problems

  6. Surface-Area-to-Volume Ratio Surface area = the amount of “covering” of the object Volume = the amount of space inside the object; the amount of space the object takes up SAcube = l × w × 6 1 cm × 1 cm × 6 = 6 cm2 Vcube = l × w × h 1 cm × 1 cm × 1 cm = 1 cm3

  7. Surface Area to Volume in Growing Cells SA SA 24 cm2 54 cm2 V V 27 cm3 8 cm3

  8. Ratio of Surface Area to Volume in Cells Largest ratio Smallest ratio

  9. Cell Growth Limitations Information crisis: too many demands placed on DNA Traffic problems: volume grows too fast relative to surface area, material exchange is insufficient

  10. Cell Division Produces two daughter cells Cell must replicate DNA before cell division. Dividing to make more, smaller cells keeps SA to V ratio high.

  11. Asexual Reproduction A single parent produces genetically identical offspring. New individuals form from the separation of cells.

  12. Sexual Reproduction Sexual reproduction involves the of two separate parent cells. Offspring inherit some genetic information from each parent. fusion

  13. Comparing Asexual and Sexual Reproduction Asexual Produce many offspring in short period Don’t need to find a mate In stable environments, genetically identical offspring thrive. If conditions change, offspring not well adapted. • Sexual • Relatively fewer offspring; growth takes more time • Need to find a mate • In changing environments, genetic diversity can be beneficial. • Offspring may be less well adapted to current conditions.

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