Assignment Due Friday

What is... LIFE??

Living Non-Living?

Organize the following into your table.. Toenail Sun Hair Nerve Cell Leaf Fire Tree bark Water Algae Bacteria

What makes something alive? Describe ways in which the “Baby” looked “alive” What characteristics of living things are not shown by the “Baby”?

10 Characteristics of Life Organization Reproduction Growth & Development Nutrition (feeding) Respiration 6. Excretion 7. Responsiveness 8. Movement 9. Homeostasis 10. Evolution

Organize the following into your table.. Toenail Sun Hair Nerve Cell Leaf Fire Tree bark Water Algae Bacteria

Origin of Life

Aristotle (384 –322 BC) Proposed the theory of spontaneous generation Also called abiogenesis Idea that living things can arise from nonliving matter Idea lasted almost 2000 years

Spontaneous Generation For centuries, people based their beliefs on their interpretations of what they saw going on in the world around them without testing their ideas They didn’t use the scientific method to arrive at answers to their questions Their conclusions were based on untested observations copyright cmassengale

Examples of Spontaneous Generation

Example #1 Observation: Every year in the spring, the Nile River flooded areas of Egypt along the river, leaving behind nutrient-rich mud that enabled the people to grow that year’s crop of food. However, along with the muddy soil, large numbers of frogs appeared that weren’t around in drier times

Example #1 Conclusion: It was perfectly obvious to people back then that muddy soil gave rise to the frogs

Example #2 Observation: In many parts of Europe, medieval farmers stored grain in barns with thatched roofs (like Shakespeare’s house). As a roof aged, it was not uncommon for it to start leaking. This could lead to spoiled or moldy grain, and of course there were lots of mice around.

Example #2 Conclusion: It was obvious to them that the mice came from the moldy grain.

Example #3 Observation: In the cities centuries ago, there were no sewers, no garbage trucks, no electricity, and no refrigeration. Sewage flowed down the streets, and chamber pots and left over food were thrown out into the streets each morning. Many cities also had major rat problems and a disease called Bubonic plague.

Example #3 Conclusion: Obviously, all the sewage and garbage turned into the rats.

Up to this point, science was based on observation and analysis…now, experiments were needed to test the hypothesis. https://www.youtube.com/watch?v=WNByRghR6sw

Disproving Spontaneous Generation

Francesco Redi copyright cmassengale

Francesco Redi (1668) In 1668, Francesco Redi, an Italian physician, did an experiment with flies and wide-mouth jars containing meat

Redi’s Experiment Redi used open & closed flasks which contained meat. His hypothesis was that rotten meat does not turn into flies. He observed these flasks to see in which one(s) maggots would develop.

Redi’s Findings He found that if a flask was closed with a lid so adult flies could not get in, no maggots developed on the rotting meat within. In a flask without a lid, maggots soon were seen in the meat because adult flies had laid eggs and more adult flies soon appeared.

Redi’s (1626-1697) Experiments Evidence against spontaneous generation: 1. Unsealed – maggots on meat 2. Sealed – no maggots on meat 3. Gauze – few maggots on gauze, none on meat copyright cmassengale

Results of Redi’s Experiments 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.

Disproving Spontaneous Generation of Microbes

Anton van Leeuwenhoek (1674) Leeuwenhoek began making and looking through simple microscopes He often made a new microscope for each specimen He examined water and visualized tiny animals, fungi, algae, and single celled protozoa; “animalcules” By end of 19th century, these organisms were called microbes

Anton van Leeuwenhoek 1632-1723 copyright cmassengale

Leeuwenhoek’s Microscope

John Needham (1745) Showed that microorganisms flourished in various soups that had been exposed to the air Claimed that there was a “life force” present in the molecules of all inorganic matter, including air and the oxygen in it, that could cause spontaneous generation to occur

Needham’s Results Needham’s experiments seemed to support the idea of spontaneous generation People didn’t realize bacteria were already present in Needham’s soups Needham didn’t boil long enough to kill the microbes

Needham’s Experiment copyright cmassengale

Lazzaro Spallanzani’s (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.

Spallanzani’s Results

Conclusion 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 Changes copyright cmassengale

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, as he published the results of an experiment he did to disproved spontaneous generation in microscopic organisms

Louis Pasteur (1822-1895) copyright cmassengale

Pasteur's Experiment - Step 1 S-shaped Flask Filled with broth The special shaped was intended to trap any dust particles containing bacteria

Pasteur's Experiment - Step 2 Flasks boiled Microbes Killed

Pasteur's Experiment - Step 3 Flask left at various locations Did not turn cloudy Microbes not found Notice the dust that collected in the neck of the flask

And so, 2000 years after it started the debate of abiogenesis vs And so, 2000 years after it started the debate of abiogenesis vs. biogenesis is settled: Biogenesis: Life comes from life, not from spontaneous generation of non-living things!!! https://www.youtube.com/watch?v=dYphAH2tKYE