How do you think evolution shapes our understanding of biology? Activator How do you think evolution shapes our understanding of biology?

New Section Title: History of Life Essential Question: How do new understandings of Earth’s history influence our understanding of biology? Discuss with your neighbor: What do you know about the history of life?

Aristotle's Thoughts Proposed the theory of spontaneous generation a.k.a. abiogenesis Living things can arise from nonliving things Lasted nearly 2000 years

Spontaneous Generation For centuries, people based their beliefs on their interpretations of what they saw. They didn’t use the scientific method

Spontaneous Generation Muddy soil yielded frogs, and moldy grain yielded mice.

Spontaneous Generation Rats and flies grew from garbage.

What Happened to this Thought? In 1668, an Italian physician did an experiment with flies and wide-mouth jars containing meat In 1668, Francesco Redi, an Italian physician, did an experiment with flies and wide-mouth jars containing meat

What Were the Results? The results of this experiment disproved the idea of spontaneous generation for larger organisms, but people still thought microscopic organisms like algae or bacteria could arise that way.

What Else Happened? Boiled soups for almost an hour and sealed containers by melting the slender necks closed. Lazzaro Spallanzani’s experiment (1765) Boiled soups for almost an hour and sealed containers by melting the slender necks closed. The soups remained clear. Later, he broke the seals & the soups became cloudy with microbes.

What Were the Results? Critics said sealed vials did not allow enough air for organisms to survive and that prolonged heating destroyed “life force” Therefore, spontaneous generation remained the theory of the time The theory finally changed… Critics said sealed vials did not allow enough air for organisms to survive and that prolonged heating destroyed “life force” Therefore, spontaneous generation remained the theory of the time

The prize was claimed in 1864 by Louis Pasteur How Do Microbes Arise? By 1860, the debate had become so heated that the Paris Academy of Sciences offered a prize for any experiments that would help resolve this conflict The prize was claimed in 1864 by Louis Pasteur The prize was claimed in 1864 by Louis Pasteur, as he published the results of an experiment he did to disproved spontaneous generation in microscopic organisms

Pasteur's Problem Hypothesis: Microbes come from cells of organisms on dust particles in the air; not the air itself. Pasteur put broth into several special S-shaped flasks Each flask was boiled and placed at various locations Boiled the broth and killed the microbes.

Pasteur's Experiment Flask left at various locations Did not turn cloudy Microbes not found Notice the dust that collected in the neck of the flask

Pasteur’s Theory of Biogenesis Proved microbes only come from other microbes (life from life)! Theory that all living things come from other living things. Disproved spontaneous generation

Endosymbiosis Hypothesis that states that large prokaryotic, unicellular organisms were invaded by smaller prokaryotic unicellular organisms. Scientists believe these smaller organisms gave rise to Chloroplast and Mitochondria (which is why they have their own DNA) thus becoming the organelles of eukaryotes.

Endosymbiosis copyright cmassengale