For thousands of years, humans believed that living things were born from nonliving things. For example, they believed maggots were born from raw meat and eels formed from river mud. How does cell theory disprove this idea of spontaneous generation?

Answer 1

Cell theory fundamentally changed our understanding of living organisms and their origins by establishing principles that countered the long-held belief in spontaneous generation—the idea that life could arise from nonliving matter. Here are the key ways cell theory disproves spontaneous generation:

1. All Living Things are Composed of Cells: One of the main tenets of cell theory is that all living organisms are made up of cells. This asserts that cells are the basic structural and functional units of life. As such, living organisms arise from existing cells, not spontaneously from nonliving materials.

2. Cells Come from Preexisting Cells: Cell theory also states that all cells come from preexisting cells through the process of cell division. This means that living organisms cannot arise from inanimate substances, as every cell originates from the division of another cell. This directly contradicts the notion of spontaneous generation, where it was thought that life could emerge from nonliving matter.

3. Microscopic Observations: Advances in microscopy allowed scientists to observe cells and their behavior. Experiments by scientists like Louis Pasteur demonstrated that microorganisms in the air contaminate sterilized liquids and that no new life forms would appear unless those cells were introduced. This further supported the idea that life comes from existing life rather than spontaneously arising from nonliving materials.

4. Experimental Evidence: Controlled experiments, such as Pasteur's swan-neck flasks experiment, showed that when flasks with sterilized broth were exposed to air through a curved neck (which allowed air but blocked microorganisms), no growth occurred. However, when the neck was removed, microorganisms from the air contaminated the broth, leading to growth. This reinforced the concept that life cannot arise spontaneously; it requires the presence of existing living organisms.

Overall, cell theory emphasizes that life is continuous and complex, originating from preexisting cells rather than arising from nonliving matter, thus thoroughly discrediting the idea of spontaneous generation.