Summary of Chapter 20: The Nature of Living Things

  • Five Characteristics of Living Things:

    1. Metabolism:
    • Ability for chemical reactions to sustain life (e.g., humans metabolizing food, plants absorbing water and sunlight).
    1. Generation:
    • Living things can reproduce and create copies (not necessarily clones).
    1. Responses:
    • Interaction with the environment and stimuli (e.g., flinching from pain).
    1. Control:
    • Maintaining homeostasis (balance within internal and external environments).
    1. Structural Components:
    • All living things have identifiable structures that sustain life.

  • Biological Organization:

    • Ranges from atomic to universal levels, focusing on cells for this chapter.

  • Discovery of the Cell:

    • Robert Hooke coined the term "cell" in 1665 while observing cork under a microscope.
    • Historical context: 1665, England, a time dominated by religious beliefs over scientific inquiry.

  • Cell Theory:

    • Developed by Schwann, Schleiden, and Virchow:
    1. All living things are composed of cells.
    2. New cells arise from existing cells.
    3. Cells are the fundamental unit of life.

  • Types of Cells:

    • Prokaryotic (simpler, e.g., bacteria) vs. Eukaryotic (complex, e.g., human body cells).

  • Cell Functionality:

    • Major components of eukaryotic cells include:
      • Cell Membrane:
      • Semipermeable, allowing selective movement of substances in and out.
      • Mitochondria:
      • Energy production center of the cell.
      • Nucleus:
      • Contains DNA and regulates cell activity.
      • Endoplasmic Reticulum:
      • Important for protein synthesis.

  • Cell Division:

    • Mitosis:
      • Asexual reproduction; one division creates two identical cells.
    • Meiosis:
      • Sexual reproduction; two divisions create four genetically diverse cells.
      • Ensures genetic diversity by halving genetic material from parents.

  • Conclusion:

    • Cells are fundamental components of all living beings. Understanding cells is crucial to understanding life itself.