History of Life

Chapter 14

Biogenesis• Biogenesis is the idea that all living things come

from other living things.• Before the 17th century it was believed that

living things could also arise from non-living things in a process from spontaneous generation…

this explains: why maggots appeared on rotting meat.

Francesco Redi experiment

• Francesco Redi was able to disprove the theory that maggots could be spontaneously generated from meat using a controlled experiment.

• demonstrating that maggots come from eggs of flies

Disproving spontaneous generation

Spallanzani’s experiment Pasteur’s experiemnt

The formation of Earth

Earth’s History

First organic compounds on Earth• In 1953, Stanley L. Miller and Harold C. Urey,

working at the University of Chicago, conducted an experiment which would change the approach of scientific investigation into the origin of life.

• Miller took molecules which were believed to represent the major components of the early Earth's atmosphere and put them into a closed system

• The gases they used were methane (CH4), ammonia (NH3), hydrogen (H2), and water (H2O). Next, he ran a continuous electric current through the system, to simulate lightning storms believed to be common on the early earth. At the end of one week, Miller observed that as much as 10-15% of the carbon was now in the form of organic compounds. Two percent of the carbon had formed some of the amino acids which are used to make proteins. Perhaps most importantly, Miller's experiment showed that organic compounds such as amino acids, which are essential to cellular life. https://www.youtube.com/watch?v=mF9U5x6

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The first life forms on Earth

• The first cells on earth were probably anaerobic prokaryotes.

• Archaea• Oxygen began

accumulating in the atmosphere about 2.7 billion years ago.

•   Cyanobacteria are photosynthetic prokaryotes that are still present today à produced oxygen.

The first Eukaryotic cells

• Endosymbiosis theory

https://www.youtube.com/watch?v=-FQmAnmLZtE