cell theory

Cell Theory

• All organisms are composed of 1 or more cells.

• The cell is the smallest functional unit of life.

• All cells are produced from other cells.

Characteristics of Living Things

• Characteristics that define what makes something living are not detailed in the transcript but generally include:

  • Growth

  • Reproduction

  • Response to stimuli

  • Metabolism

  • Homeostasis

  • Cellular organization

  • Adaptation through evolution

Historical Views on Life

• Abiogenesis:

  • Belief that organisms could arise from non-living matter.

  • Example: Maggots in rotting meat attributed to spontaneous generation.

  • Aristotle proposed this theory without experimental evidence.

• Redi’s Experiment:

  • First experimental test against spontaneous generation by Francesco Redi.

  • Hypothesis: Maggots are from flies landing on meat.

  • Experiment: Compared covered and uncovered jars; only uncovered showed maggots.

• Louis Pasteur’s Contribution:

  • Proposed the active principle; microorganisms in air contribute to fermentation.

  • Formulated the theory of Biogenesis: living organisms arise only from other living organisms.

Discovering Cells

• Robert Hooke:

  • Used a microscope (30x magnification) to observe cork; named cells after the tiny rooms.

• Anthony van Leeuwenhoek (AVL):

  • First to describe single-celled organisms; observed “animalcules” from teeth scrapings (270x magnification).

Contributions of Schwann and Schleiden

• Schwann and Schleiden:

  • Studied microscopic structure of plants and animals, leading to the conclusion that all are made of cells.

Rudolf Virchow

• Virchow’s Contribution:

  • Proposed that cells arise from existing cells via division (mitosis) contrary to earlier debates about cell formation.