Evolutionary Scientists

Francesco Redi 1668 First to disprove spontaneous generation First to be recognized for having a control group in an experiment

John Needham 1745 Attempted to prove spontaneous generation with microscopic organisms Heated chicken broth in a flask to kill all living microscopic organisms Let broth cool and sit. Broth became cloudy with microorganisms This gave Needham proof that microorganisms came from the broth

Lazzaro Spallanzani Repeated Needham’s experiment He removed the air from the flask by creating a vacuum after the broth was heated No microorganisms grew disproving spontaneous generation of microorganisms Some believed that all Spallanzani proved was that spontaneous generation could not occur without air

Louis Pasteur 1850s Designed an experiment to disprove spontaneous generation once and for all Performed a variation of Needham’s and Spallanzani’s experiments by using a special flask that allowed air but trapped contaminants so it could not get to the flask Pasteur showed that microorganisms lived in the air but was not formed from the air

Pasteur’s other accomplishments First to determine that yeast is responsible for fermentation Developed the germ theory Created vaccines for rabies and anthrax Created pasteurization Experiment led to the law of Biogenesis: living things come from other living things

Jean-Baptiste de Lamarck Believed that as the environment changed, organisms changed their behavior to survive As an organism used a body part to adapt, that body part would improve over time or shrink if not used. ‘First Law’ Organisms passed on characteristics to their offspring. ‘Second Law’ He believed organisms changed over time from simple to more complex

Example: How did Lamarck believe giraffes acquired longer necks? By stretching their necks to eat leaves from tall trees, giraffes could grow their necks and pass on the longer necks to their offspring.

Charles Darwin 1809-1882 Considered the father of evolution Went on a 5 year journey on the H.M.S. Beagle to study specimens

Galapagos Islands Studied the birds on these islands If the birds migrated from the mainland, then they would be the same on the island. If the birds were created differently then they would be different from the mainland birds. Darwin found the birds were not exactly the same nor different so he thought the birds evolved over time in order to adapt to the island.

On the Origin of Species: Darwin’s book of theories All populations show the ability to change from one generation to the next Competition and variation lead to natural selection (organisms that survive an environment are more adapted. The strongest survive) survival of the fittest Descent of modification: natural selection leads to new species or organs formed by a steady accumulation of modifications

On the Origin of Species cont… 4. All living organisms have a common ancestor that evolved over time that have either become extinct or exist today.

Both Lamarck and Darwin believed in species changed over time but neither had knowledge of genetics

Thomas Malthus 1766-1834 Believed that plants and animals reproduced more offspring than could survive (the struggle for existence) For example, the rate of reproduction in humans would one day be greater than the resources (food supply) to sustain them. Darwin used Malthus’ idea to support his ideas of natural selection and survival of the fittest

Charles Lyell 1797-1875 Geologist and paleontologist Ideas were known as uniformitarianism (geologic forces transformed the surface of Earth over a long period of time) Darwin used Lyell’s ideas to support natural selection of living organisms over a long period of time

Alfred Russel Wallace Had a paper to be published on the same ideas as Darwin. Together, they published a paper on natural selection. A year later, Darwin published On the Origin of Species. Darwin received the recognition.

Remember… Natural selection choose the most advantageous trait for an organism so those traits are passed on to future generations. The only way scientists have observed changes in genes is by mutations. Random mutations with natural selection are thought to be the driving force behind evolution