INSTRUCTIONAL OBJECTIVES

1. INTRODUCTION TO ORIGIN OF LIFE.2.LEARN THE SPONTANEOUS GENERATION SPONTANEOUS GENERATION

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ORIGIN OF LIFEORIGIN OF LIFE

ARISTOTLE (322–384 BC)ARISTOTLE (322–384 BC)

Proposed the theory of Proposed the theory of spontaneous generationspontaneous generation

Also called Also called abiogenesisabiogenesis Idea that Idea that living things can living things can

arise from nonlivingarise from nonliving matter matter Idea lasted almost Idea lasted almost 2000 2000

yearsyears

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SPONTANEOUS SPONTANEOUS GENERATIONGENERATION

For centuriesFor centuries, , people basedpeople based their their beliefsbeliefs onon their interpretations of their interpretations of what they sawwhat they saw going on in the going on in the world around them without testing world around them without testing their ideastheir ideas

They They didn’t use the scientific didn’t use the scientific methodmethod to arrive at answers to to arrive at answers to their questionstheir questions

Their conclusions were based on Their conclusions were based on untested observationsuntested observations

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EXAMPLES OF EXAMPLES OF SPONTANEOUS SPONTANEOUS GENERATIONGENERATION

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EXAMPLE #1EXAMPLE #1

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

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

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EXAMPLE #2EXAMPLE #2

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

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

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EXAMPLE #3EXAMPLE #3

Observation: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. refrigeration. Sewage flowed Sewage flowed down the streets, and down the streets, and chamber pots and left over chamber pots and left over foodfood were thrown out into the were thrown out into the streets each morning. Many streets each morning. Many cities also had major cities also had major rat rat problemsproblems and a disease called and a disease called Bubonic plagueBubonic plague..

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EXAMPLE #3EXAMPLE #3

Conclusion:Conclusion: Obviously, all Obviously, all the the sewage and garbage 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, refrigerators, the mandatory, daily trip to the butcher shop, daily trip to the butcher shop, especially in summer, especially in summer, meant meant battling the flies around the battling the flies around the carcassescarcasses. Typically, carcasses . Typically, carcasses were “hung by their heels,” and were “hung by their heels,” and customers selected which chunk customers selected which chunk the butcher would carve off for the butcher would carve off for them. them.

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EXAMPLE #4EXAMPLE #4

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

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ABIOGENESIS ABIOGENESIS RECIPESRECIPES

Recipe for bees:Recipe for bees:

Kill a young bullKill a young bull, and , and bury itbury it in an upright in an upright position so that its position so that its horns horns protrude from the protrude from the groundground. After a month, a . After a month, a swarm of bees will fly out swarm of bees will fly out of the corpse. of the corpse.

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ABIOGENESIS RECIPESABIOGENESIS RECIPES Recipe for mice:Recipe for mice:

Place a Place a dirty shirtdirty shirt or some rags in or some rags in an an open pot or barrelopen pot or barrel containing a containing a few grains of few grains of wheatwheat or some wheat bran, and or some wheat bran, and in in 21 days21 days, mice will appear. , mice will appear. There will be adult males and There will be adult males and females present, and they will females present, and they will be capable of mating and be capable of mating and reproducing more mice.reproducing more mice.

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INSTRUCTIONAL OBJECTIVES :

1. INTRODUCTION TO ORIGIN OF LIFE.2.LEARN BIOGENESIS

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1.THEY ARE MADE UP OF CELL2.THEY BREATH 3.THEY OBTAIN AND USE ENERGY4.THEY GROW AND DEVELOP5.THEY RESPONDS TO THE STIMULUS6.THEY REPRODUCE7.THEY CARRY THE GENETIC INFORMATIONS8.THEY MAINTAIN A STABLE INTERNAL CONDITION9.THEY CHANGE OVERTIME

METABOLISM AND HOMEOSTASIS

Metabolism:

Total chemical reaction occurring in an organism .

Homeostasis:

Self regulating ,self balancing system in an organism

DISPROVING DISPROVING SPONTANEOUS SPONTANEOUS GENERATIONGENERATION

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FRANCESCO REDI FRANCESCO REDI (1668)(1668)

In 1668, Francesco In 1668, Francesco RediRedi, an , an Italian physician, did an Italian physician, did an experiment with experiment with fliesflies and and wide-mouth jars containing wide-mouth jars containing meatmeat

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REDI’S EXPERIMENTREDI’S EXPERIMENT

Redi used Redi used open & closed open & closed flasksflasks which which contained meatcontained meat..

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

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

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REDI’S FINDINGSREDI’S FINDINGS He found that if a flask was He found that if a flask was closedclosed with a lid so with a lid so adult adult flies could not get in, no flies could not get in, no maggotsmaggots developed on the developed on the rotting meat within.rotting meat within.

In a flask In a flask without a lidwithout a lid, , maggots soon were seenmaggots soon were seen in in the meat because adult flies the meat because adult flies had laid eggs and more had laid eggs and more adult flies soon appeared.adult flies soon appeared.

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REDI’S (1626-1697) EXPERIMENTS

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Evidence against spontaneous Evidence against spontaneous generation:generation:

1. 1. Unsealed Unsealed – maggots on meat– maggots on meat2. 2. SealedSealed – no maggots on meat – no maggots on meat3. 3. GauzeGauze – few maggots on gauze, none on – few maggots on gauze, none on

meatmeat

RESULTS OF REDI’S RESULTS OF REDI’S EXPERIMENTSEXPERIMENTS

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

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FRANCESCO REDIFRANCESCO REDI26

DID REDI USE THE DID REDI USE THE SCIENTIFIC METHOD?SCIENTIFIC METHOD?

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THE SCIENTIFIC METHODTHE SCIENTIFIC METHOD28

ObservationObservation

HypothesisHypothesis

ExperimentExperiment

Accept, Reject, or Modify Accept, Reject, or Modify hypothesishypothesis

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

Rotten meat does Rotten meat does not turn into flies. not turn into flies. Only flies can Only flies can make more flies.make more flies.

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STEP 3 - TESTINGSTEP 3 - TESTING

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

Control groupControl group — These jars of meat — These jars of meat were set out were set out without lidswithout lids so the meat so the meat would be exposed to whatever it might would be exposed to whatever it might be in the butcher shop.be in the 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 absence of Presence or absence of fliesflies and maggots observed and maggots observed in each jar was in each jar was recordedrecorded..

Control groupControl group – flies – flies entered, laid eggs, & entered, laid eggs, & maggots emergedmaggots emerged

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 - STEP 5 - CONCLUSIONCONCLUSION

Only flies can make more fliesOnly flies can make more flies. In the . In the uncovered jarsuncovered jars, flies entered and laid , flies entered and laid eggs on the meat. Maggots hatched eggs on the meat. Maggots hatched from these eggs and grew into more from these eggs and grew into more adult flies. Adult flies laid eggs on the adult flies. Adult flies laid eggs on the gauze on the gauze-covered jars. These gauze on the gauze-covered jars. These eggs or the maggots from them eggs or the maggots from them dropped through the gauze onto the dropped through the gauze onto the meat. In the meat. In the sealed jarssealed jars, no flies, , no flies, maggots, nor eggs could enter, thus maggots, nor eggs could enter, thus none were seen in those jars. Maggots none were seen in those jars. Maggots arose only where flies were able to lay arose only where flies were able to lay eggs. eggs. This experiment disproved the This experiment disproved the idea of spontaneous generation for idea of spontaneous generation for larger organisms.larger organisms.

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DISPROVING DISPROVING SPONTANEOUS SPONTANEOUS

GENERATION OF GENERATION OF MICROBESMICROBES

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ANTON VAN LEEUWENHOEK ANTON VAN LEEUWENHOEK (1674)(1674)

Leeuwenhoek began Leeuwenhoek began makingmaking and and looking through looking through simple microscopessimple microscopes

He often made a new microscope He often made a new microscope for each specimenfor each specimen

He He examined waterexamined water and visualized and visualized tiny animals, fungi, algae, and tiny animals, fungi, algae, and single celled protozoa; 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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ANTON VAN ANTON VAN LEEUWENHOEK 1632-LEEUWENHOEK 1632-

1723172336

LEEUWENHOEK’S LEEUWENHOEK’S MICROSCOPEMICROSCOPE

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JOHN NEEDHAM (1745)JOHN NEEDHAM (1745)

Showed that microorganisms Showed that microorganisms flourished in various soups that flourished in various soups that had been exposed to the airhad been exposed to the air

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

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NEEDHAM’S RESULTSNEEDHAM’S RESULTS

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

People People didn’t realizedidn’t realize bacteria were already bacteria were already present in Needham’s soupspresent in Needham’s soups

Needham Needham didn’t boil long didn’t boil long enoughenough to kill the microbes to kill the microbes

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NEEDHAM’S NEEDHAM’S EXPERIMENTEXPERIMENT

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LAZZARO SPALLANZANI’S LAZZARO SPALLANZANI’S (1765)(1765)

Boiled soups for almost an Boiled soups for almost an hourhour and sealed containers and sealed containers by by melting the slender necks melting the slender necks closedclosed.

The The soups remained clearsoups remained clear..

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

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SPALLANZANI’S SPALLANZANI’S RESULTSRESULTS

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CONCLUSIONCONCLUSION

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

Therefore, Therefore, spontaneous spontaneous generation remainedgeneration remained the the theory of the timetheory of the time

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THE THEORY THE THEORY FINALLY CHANGESFINALLY CHANGES

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HOW DO MICROBES HOW DO MICROBES ARISE?ARISE?

By By 18601860, the debate had become so heated , the debate had become so heated that the that the Paris Academy of SciencesParis Academy of Sciences offered a offered a prizeprize for any experiments that would help for any experiments that would help resolve this conflictresolve this conflict

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

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LOUIS PASTEUR (1822-LOUIS PASTEUR (1822-1895)1895)

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PASTEUR'S PROBLEMPASTEUR'S PROBLEM

Hypothesis:Hypothesis: Microbes Microbes come from cells of come from cells of organisms on dust particles organisms on dust particles in the air; not the air itself.in the air; not the air itself.

Pasteur put broth into Pasteur put broth into several special several special S-shaped S-shaped flasksflasks

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

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PASTEUR'S PASTEUR'S EXPERIMENT - EXPERIMENT - STEP 1STEP 1

S-shaped FlaskS-shaped Flask Filled withFilled with broth broth The special shaped flask was The special shaped flask was

intended to intended to trap any dust trap any dust particles containing bacteriaparticles containing bacteria

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PASTEUR'S PASTEUR'S EXPERIMENT - EXPERIMENT - STEP 2STEP 2 FlasksFlasks boiledboiled

Microbes KilledMicrobes Killed

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PASTEUR'S PASTEUR'S EXPERIMENT - EXPERIMENT - STEP 3STEP 3

Flask left at various Flask left at various locationslocations

Did Did not turn cloudynot turn cloudy Microbes not foundMicrobes not found Notice the Notice the dustdust that that

collected in the neckcollected in the neck of the flask of the flask

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PASTEUR'S PASTEUR'S EXPERIMENTAL EXPERIMENTAL

RESULTSRESULTS51

THE THEORY OF BIOGENESISTHE THEORY OF BIOGENESIS

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

Proved microbes only come from other microbes Proved microbes only come from other microbes

(life from life) - (life from life) - biogenesisbiogenesis

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Figure 1.3

REVIEWREVIEW

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EVIDENCE PRO AND CONEVIDENCE PRO AND CON

1668: 1668: Francisco RediFrancisco Redi filled six filled six jars with decaying meat.jars with decaying meat.

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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?

EVIDENCE PRO AND CONEVIDENCE PRO AND CON 1745: 1745: John NeedhamJohn Needham put put

boiled nutrient broth into boiled nutrient broth into covered flasks.covered flasks.

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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?

EVIDENCE PRO AND CON 1765: 1765: Lazzaro SpallanzaniLazzaro Spallanzani boiled nutrient boiled nutrient

solutions in flasks.solutions in flasks.

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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?

EVIDENCE PRO AND CONEVIDENCE PRO AND CON 1861: 1861: Louis PasteurLouis Pasteur

demonstrated that demonstrated that microorganisms are present in microorganisms are present in the air.the air.

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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?