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Origin of Origin of LifeLife

Created by Coach BlockerSchley County Middle School

Ellaville, Georgia

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Aristotle (384 –322 BC)Aristotle (384 –322 BC)

Proposed the theory Proposed the theory of of spontaneous spontaneous generationgenerationIdea that living Idea that living things can arise from things can arise from nonliving matternonliving matter Idea lasted almost Idea lasted almost 2000 years2000 years

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Spontaneous GenerationSpontaneous GenerationFor centuries, people based For centuries, people based their beliefs on their their beliefs on their interpretations of what they saw interpretations of what they saw going on in the world around going on in the world around them without testing their ideasthem without testing their ideas They didn’t use the scientific They didn’t use the scientific method to arrive at answers to method to arrive at answers to their questionstheir questionsTheir conclusions were based Their conclusions were based on untested observationson untested observations

Spontaneous Generation

Abiogenesis- living organisms can arise spontaneously from non-living matter.

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Examples of Examples of SpontaneouSpontaneous Generations Generation

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Example #1Example #1

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

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

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Example #2Example #2

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

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Example #2Example #2

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

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Example #3Example #3Observation:Observation: In the cities In the cities

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

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Example #3Example #3

Conclusion:Conclusion: Obviously, all Obviously, all the sewage and garbage the sewage and garbage turned into the ratsturned into the rats.

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Example #4Example #4

Observation:Observation: Since there were no Since there were no refrigerators, the mandatory, daily refrigerators, the mandatory, daily trip to the butcher shop, trip to the butcher shop, especially in summer, meant especially in summer, meant battling the flies around the battling the flies around the carcasses (dead animals). carcasses (dead animals). Typically, carcasses were “hung Typically, carcasses were “hung by their heels,” and customers by their heels,” and customers selected which chunk the butcher selected which chunk the butcher would carve off for them. would carve off for them.

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Example #4Example #4

Conclusion: Obviously, the rotting Obviously, the rotting meat that had been hanging in the meat that had been hanging in the sun all day was the source of the sun all day was the source of the flies. flies.

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Disproving Disproving SpontaneouSpontaneou

s s GenerationGeneration

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Francesco Redi (1668)Francesco Redi (1668)

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

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Redi’s ExperimentRedi’s Experiment

Redi used open & closed Redi used open & closed flasks which contained flasks which contained meat.meat.

His His hypothesishypothesis was that was that rotten meat does not turn rotten meat does not turn into flies.into flies.

He observed these flasks He observed these flasks to see in which one(s) to see in which one(s) maggots would develop.maggots would develop.

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Redi’s (1626-1697) Experiments

Evidence against spontaneous Evidence against spontaneous generation:generation:

1. Unsealed – maggots on meat1. Unsealed – maggots on meat2. Sealed – no maggots on meat2. Sealed – no maggots on meat3. Gauze – few maggots on gauze, none on 3. Gauze – few maggots on gauze, none on

meatmeat

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Results of Redi’s ExperimentsResults of Redi’s Experiments

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

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Did Redi Use Did Redi Use the Scientific the Scientific

Method?Method?

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The Scientific MethodThe Scientific MethodAsk A Question, Hypothesis, Experiment, Ask A Question, Hypothesis, Experiment, Analyze, Conclusion, Accept, Reject, or Analyze, Conclusion, Accept, Reject, or

Modify the hypothesisModify the hypothesis

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Step 1 - ObservationStep 1 - Observation

There were flies around There were flies around meat carcasses at the meat carcasses at the Butcher shop.Butcher shop.

Where do the flies come Where do the flies come from?from?

Does rotting meat turn Does rotting meat turn into or produce rotting into or produce rotting flies?flies?

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Step 2 - HypothesisStep 2 - Hypothesis

If rotting meat If rotting meat is exposed to is exposed to flies, then the flies, then the adult flies will adult flies will lay eggs in the lay eggs in the rotting meat, rotting meat, because the because the maggots will maggots will use the rotting use the rotting meat for food.meat for food.

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Step 3 - ExperimentationStep 3 - Experimentation

Wide-mouth jarsWide-mouth jars each containing a piece each containing a piece of meat were subjected to several of meat were subjected to several variations of variations of “openness”“openness” while all while all other other variables were kept the same.variables were kept the same.

Control groupControl group — These jars of meat were — These jars of meat were set out set out without lidswithout lids so the meat would be so the meat would be exposed to whatever it might be in the exposed to whatever it might be in the butcher shop.butcher shop.

Experimental group(s)Experimental group(s) — One group of — One group of jars were jars were sealedsealed with lids, and another with lids, and another group of jars had gauze placed over group of jars had gauze placed over them.them.

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Step 4 - DataStep 4 - Data

Presence or absencePresence or absence of flies of flies and maggots observed in and maggots observed in each jar was recorded.each jar was recorded.

Control groupControl group – flies entered, – flies entered, laid eggs, & maggots laid eggs, & maggots emergedemerged

Gauze coveredGauze covered – flies on – flies on gauze, but not in jargauze, but not in jar

Sealed jarsSealed jars – No maggots or – No maggots or flies on the meatflies on the meat

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Step 5 - ConclusionStep 5 - ConclusionOnly flies can make more fliesOnly flies can make more flies. In the . In the

uncovered jarsuncovered jars, flies entered and laid eggs on , flies entered and laid eggs on the meat. Maggots hatched from these eggs the meat. Maggots hatched from these eggs

and grew into more adult flies. Adult flies laid and grew into more adult flies. Adult flies laid eggs on the gauze on the gauze-covered jars. eggs on the gauze on the gauze-covered jars.

These eggs or the maggots from them These eggs or the maggots from them dropped through the gauze onto the meat. In dropped through the gauze onto the meat. In the the sealed jarssealed jars, no flies, maggots, nor eggs , no flies, maggots, nor eggs could enter, thus none were seen in those could enter, thus none were seen in those jars. Maggots arose only where flies were jars. Maggots arose only where flies were

able to lay eggs. able to lay eggs. This experiment disproved This experiment disproved the idea of spontaneous generation for larger the idea of spontaneous generation for larger

organisms.organisms.

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Disproving Disproving Spontaneous Spontaneous Generation of Generation of

MicrobesMicrobes

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Anton van Leeuwenhoek 1632-Anton van Leeuwenhoek 1632-17231723

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Anton van Leeuwenhoek Anton van Leeuwenhoek (1674)(1674)

Leeuwenhoek began making and Leeuwenhoek began making and looking through looking through simple simple microscopesmicroscopes

He examined pond water and He examined pond water and observed tiny animals, fungi, observed tiny animals, fungi, algae, and single celled protozoa; algae, and single celled protozoa; “animalcules”“animalcules”

By end of 19By end of 19thth century, these century, these organisms were called organisms were called microbesmicrobes

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Leeuwenhoek’s MicroscopeLeeuwenhoek’s Microscope

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John Needham (1745)John Needham (1745)

He showed that He showed that microorganisms flourished in microorganisms flourished in various soups that had been various soups that had been exposed to the airexposed to the air

He claimed that there was a He claimed that there was a “life force” “life force” present in the present in the molecules of all inorganic molecules of all inorganic matter, including air and the matter, including air and the oxygen in it, that could cause oxygen in it, that could cause spontaneous generationspontaneous generation to to occur.occur.

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Needham’s ResultsNeedham’s Results

Needham’s experiments Needham’s experiments seemed to supportseemed to support the idea the idea of of spontaneous generation.spontaneous generation.

People didn’t realize bacteria People didn’t realize bacteria were were alreadyalready present in present in Needham’s soups.Needham’s soups.

Needham Needham didn’t boildidn’t boil long long enough to kill the microbes.enough to kill the microbes.

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Needham’s ExperimentNeedham’s Experiment

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Lazzaro Spallanzani’s (1765)Lazzaro Spallanzani’s (1765)Boiled soups for almost Boiled soups for almost

an hour and sealed an hour and sealed containers by melting the containers by melting the slender necks closedslender necks closed.

The soups remained The soups remained clear.clear.

Later, he broke the seals Later, he broke the seals & the soups became & the soups became cloudy with microbes. cloudy with microbes.

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Spallanzani’s ResultsSpallanzani’s Results

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ConclusionConclusion

Critics said sealed vials Critics said sealed vials did not allow enough air did not allow enough air for organisms to survive for organisms to survive and that prolonged and that prolonged heating destroyed heating destroyed “life “life force”force”..

Therefore, spontaneous Therefore, spontaneous generation remained the generation remained the theory of the time.theory of the time.

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The Theory The Theory Finally Finally

ChangesChanges

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How Do Microbes Arise?How Do Microbes Arise?

By 1860, the debate had become By 1860, the debate had become so heated that the Paris Academy so heated that the Paris Academy of Sciences offered a prize for of Sciences offered a prize for any experiments that would help any experiments that would help resolve this conflict.resolve this conflict.

The prize was claimed in 1864 by The prize was claimed in 1864 by Louis PasteurLouis Pasteur, as he published , as he published the results of an experiment he the results of an experiment he did to disproved spontaneous did to disproved spontaneous generation in microscopic generation in microscopic organisms.organisms.

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Louis Pasteur (1822-1895)Louis Pasteur (1822-1895)

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Pasteur's ProblemPasteur's Problem HypothesisHypothesis:: If the dust in the air If the dust in the air

is not allowed into broth, then is not allowed into broth, then microbes will not exist in broth, microbes will not exist in broth, because microbes live and feed because microbes live and feed on dust particles in theon dust particles in the

Pasteur put broth into several Pasteur put broth into several special S-shaped flasks to trap special S-shaped flasks to trap dust particles.dust particles.

Each flask was boiled and Each flask was boiled and placed at various locations.placed at various locations.

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Pasteur's Experiment - Pasteur's Experiment - Step Step 11

Create S-shaped Create S-shaped Flask - Flask - The special The special shape was intended shape was intended to trap any dust to trap any dust particles containing particles containing bacteria.bacteria.

Fill with broth Fill with broth

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Pasteur's Experiment - Pasteur's Experiment - Step Step 22

Flasks boiledFlasks boiled

Microbes KilledMicrobes Killed

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Pasteur's Experiment - Pasteur's Experiment - Step Step 33

Flask left at Flask left at various locationsvarious locations

Did not turn Did not turn cloudycloudy

Microbes not Microbes not foundfound

Notice the dust Notice the dust that collected in that collected in the neck of the the neck of the flask flask

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Pasteur's Experimental Pasteur's Experimental ResultsResults

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Pasteur’s S-shaped flask kept Pasteur’s S-shaped flask kept microbes out but let air in.microbes out but let air in.

Proved microbes only come from Proved microbes only come from other microbes (life from life) - other microbes (life from life) -

biogenesisbiogenesis

The Theory of BiogenesisThe Theory of Biogenesis

Review

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1668: 1668: Francisco RediFrancisco Redi

Conditions:Conditions: Results:Results:3 jars covered with 3 jars covered with fine netfine net

No maggotsNo maggots

3 open jars3 open jars Maggots appearedMaggots appeared

From where did the maggots come?From where did the maggots come?

What was the purpose of the sealed jars?What was the purpose of the sealed jars?

SSpontaneous generation or biogenesis?pontaneous generation or biogenesis?

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1745: 1745: John NeedhamJohn Needham

Conditions:Conditions: Results:Results:Nutrient broth Nutrient broth heated, then heated, then placed in sealed placed in sealed flaskflask

Microbial growthMicrobial growth

From where did the microbes come?From where did the microbes come?

SSpontaneous generation or pontaneous generation or biogenesis?biogenesis?

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1765: 1765: Lazzaro SpallanzaniLazzaro Spallanzani

Conditions:Conditions: Results:Results:

Nutrient broth Nutrient broth placed in flask, placed in flask, heated, then heated, then sealedsealed

No microbial No microbial growthgrowth

SSpontaneous generation or pontaneous generation or biogenesis?biogenesis?

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1861: 1861: Louis PasteurLouis Pasteur

Conditions:Conditions: Results:Results:Nutrient broth Nutrient broth placed in flask, placed in flask, heated, not sealedheated, not sealed

Microbial growthMicrobial growth

Nutrient broth Nutrient broth placed in flask, placed in flask, heated, then sealedheated, then sealed

No microbial No microbial growthgrowth

SSpontaneous generation or biogenesis?pontaneous generation or biogenesis?

Twenty years after Pasteur’s experiment, disproving spontaneous generation, Thomas Henry Huxley first used the term biogenesis.

The concept of biogenesis is one of the most completely demonstrated principles in biology.

For life to come into being, scientists agree that four developments MUST have occurred. These include the following:1. The formation of simple organic compounds

important to life. (Amino Acids)2. The formation of complex organic compounds.

(Proteins)3. The concentration and enclosure of these organic

compounds. (Cell Membrane)4. The linking of chemical reactions involved in

growth. (Photosynthesis and Cellular Respiration)

The Heterotroph Hypothesis:

In the 1930’s, the Russian scientist, A. I. Oparin, presented a hypothesis to explain how the first living thing might have developed. This theory was called the Heterotroph Hypothesis.

He proposed that: Energy from ultraviolet light, lightning and volcanic

heat caused chemical reactions to occur in the atmosphere.

These reactions created small organic molecules that dissolved in oceans.

Eventually, a large quantity of organic chemicals accumulated. (Amino Acids)

According to Oparin, the first life must have evolved from these organic compounds.

In the 1950’s Stanley Miller tried to recreate conditions on Earth under which life may have formed. He used:

-water to represent the oceans

-Methane, Ammonia, Hydrogen and Water Vapor as the earth’s early atmosphere

-electrical sparks as lightning.

After his experiment, he found numerous organic compounds including amino acids. Although amino acids are the building blocks of protein, Miller had NOT created life.

He had shown that conditions like those on early Earth could produce some of the chemicals present in living things.