Cell Growth, Division, and Reproduction Summary

Key Questions

  • Difficulties faced by cells as they increase in size.

  • Comparison of asexual and sexual reproduction.

Vocabulary

  • Cell division

  • Asexual reproduction

  • Sexual reproduction

Cell Growth and Division

  • Growth in living organisms occurs primarily through cell division, not by increasing cell size.

  • Limits to cell size are due to inefficiencies in nutrient and waste exchange as size increases.

  • Increased demand on DNA with growth leads to potential information overload.

Surface Area to Volume Ratio

  • The exchange rate of materials depends on surface area and volume.

  • Larger cells have a reduced surface area to volume ratio, which limits efficiency.

  • Important ratios:

    • 1 cm cube: 6:1

    • 2 cm cube: 3:1

    • 3 cm cube: 2:1

Problems of Overgrowth

  • Comparing a cell's growth to a traffic jam: as it grows, material exchange becomes inefficient.

  • DNA remains constant while the cell grows, causing an information crisis.

Cell Division

  • Cell division reduces cell volume and increases the surface area to volume ratio, enhancing material exchange.

  • DNA replication occurs before cell division, ensuring each daughter cell inherits a complete copy of genetic information.

Reproduction Methods

  • Asexual Reproduction: Involves a single parent, results in genetically identical offspring, quick population increase. Examples include: binary fission in bacteria, budding in hydras, vegetative propagation in plants.

  • Sexual Reproduction: Involves fusion of reproductive cells from two parents, resulting in genetic diversity. Common in most multicellular organisms.

Advantages and Disadvantages

  • Asexual reproduction: Fast and efficient under favorable conditions; lacks genetic diversity, which may be detrimental during environmental changes.

  • Sexual reproduction: Slower but leads to genetic diversity that can enhance survival during changes in environment.