Theories about the evolution of organic molecules

1. Theories about the evolution of organic molecules Year 11:Biology

2. Describe two scientific theories relating to the evolution of the chemicals of life and discuss their significance in understanding the origin of life

3. Spontaneous generation • As far back as the time of Aristotle, humans thought that life spontaneously arises from non-living matter. • They saw maggots appear in rotting meat

4. This concept of spontaneous generation was an accepted ‘fact’ and was not scientifically tested until 1668. • Francesco Redi an Italian physician, demonstrated that maggots in decaying meat came from eggs laid by flies

5. About 100 years later Lazzaro Spallanzani showed that the microorganisms that appeared in broth came from the air • However his experimental technique was not sufficient to exclude spontaneous generation

6. It was almost another 100 years, 1862, before French scientist Louis Pasteur convinced people that the spontaneous generation did not occur • DIAGRAMS

7. Pasteur’s work and work of others such as Virchow established the statement that ‘all life comes from pre-existing life’ • This presumed that first living thing or things had to arise somewhere, sometime, somehow