Cell Growth, Division, and Reproduction

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Cell Growth, Division, and Reproduction
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Learning Objectives

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

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Limits to Cell Size
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A Visual Analogy
Information overload
Traffic problems
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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
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Surface Area to Volume in Growing Cells
SA
SA
24 cm2
54 cm2
V
V
8 cm3
27 cm3
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Ratio of Surface Area to Volume in Cells
Largest ratio
Smallest ratio
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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

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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.

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Asexual Reproduction

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

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Sexual Reproduction

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

fusion
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Comparing Asexual and Sexual Reproduction

• Asexual
• Produce many offspring in short period
• Dont 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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Student Worksheet Answers