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![Confession Bear | THE LATE 17TH CENTURY WAS A PERIOD OF GREAT SCIENTIFIC
DISCOVERY. WHILE MANY PEOPLE OFFERED THEORIES WITHOUT
EXPERIMENTATION OR EVIDENCE, ENGLISH SCIENTIST ROBERT
HOOKE BELIEVED THAT GOOD SCIENCE RESULTED FROM MAKING
OBSERVATIONS ON WHAT YOU COULD SEE. IN HIS TWENTIES, HE
WROTE A BOOK OF HIS OBSERVATIONS AND DRAWINGS OF THE NAT-
URAL WORLD CALLED MICROGRAPHIA, MEANING “TINY DRAWINGS.”
IT WAS FIRST PUBLISHED IN 1665. IN THIS ONE BOOK, HOOKE
PRESENTED HIS IDEAS ABOUT THE LIFE CYCLE OF MOSQUITOES, THE
ORIGIN OF CRATERS ON THE MOON, AND FOSSILS. BUT HOOKE IS
MOST REMEMBERED FOR INCLUDING DRAWINGS OF WHAT HE SAW
THROUGH A MICROSCOPE.
HOOKE DEVELOPED HIS OWN VERSION OF THE COMPOUND MICROSCOPE, AND
IT WAS ONE OF THE BEST AVAILABLE AT THE TIME. TODAY, HIS MOST FAMOUS
DRAWING FROM MICROGRAPHIA IS A DRAWING OF CORK—THE SAME KIND OF
CORK THAT IS USED IN CORKBOARDS AND BOTTLE STOPPERS. SINCE CORK IS MADE
FROM THE BARK OF THE CORK OAK TREE, IT IS ESSENTIALLY DEAD PLANT TISSUE.
USING HIS MICROSCOPE, HOOKE LOOKED AT VERY THIN SLICES OF CORK. HE
NOTICED WHAT LOOKED LIKE LITTLE ROOMS (BELOW RIGHT). BECAUSE OF THIS,
HE CALLED THESE SHAPES CELLS, ANOTHER WORD FOR ROOMS. WITH THIS SIMPLE
OBSERVATION, HOOKE INTRODUCED AN IDEA THAT WOULD BECOME THE BASIS OF
NEW FIELDS IN BIOLOGY—BUT NOT FOR ALMOST 200 YEARS!52 53
52 NGCCCO1
53 NGSPCC1
HOOKE’S MICROSCOPE
CORK TREE CORK CELLS
THE HISTORY OF CELL THEORY ACTIVITY 4
CELLS 17
ANTON VAN LEEUWENHOEK (1632–1723)
ANTON VAN LEEUWENHOEK (LAY-VUN-HOOK) WAS A CLOTH SALESMAN IN
HOLLAND AND AN AMATEUR SCIENTIST. HE KNEW HOW TO MAKE VERY SIMPLE
MICROSCOPES. (TODAY THEY WOULD BE CONSIDERED MAGNIFYING GLASSES.)
BUT HE DID NOT BECOME INTERESTED IN STUDYING THE MICROSCOPIC WORLD
UNTIL HE READ HOOKE’S MICROGRAPHIA, WHICH WAS A VERY POPULAR BOOK
AT THE TIME.
LEEUWENHOEK’S SKILL AT BUILDING MICROSCOPES (LIKE THE ONE SHOWN
AT RIGHT) ENABLED HIM TO MAGNIFY OBJECTS OVER 200 TIMES.IN 1673,
LEEUWENHOEK DESCRIBED WHAT HE SAW IN A DROP OF WATER: “. . . WRETCHED
BEASTIES. THEY STOP, THEY STAND STILL . . . AND THEN TURN THEMSELVES
ROUND . . . THEY [ARE] NO BIGGER THAN A FINE GRAIN OF SAND.” BY EXAM-
INING SCRAPINGS FROM HIS TEETH, HE FOUND ADDITIONAL EVIDENCE OF
THESE “MANY VERY LITTLE LIVING ANIMALCULES, VERY PRETTILY A-MOVING.”
LEEUWENHOEK WAS ONE OF THE FIRST PEOPLE TO OBSERVE AND RECORD
MICROSCOPIC LIVING THINGS. HE CONTINUED HIS OBSERVATIONS UNTIL THE
END OF HIS LIFE.54 55 56 57
MATTHIAS JAKOB SCHLEIDEN (1804–1881)
THEODOR SCHWANN (1810–1882)
KARL THEODOR ERNST VON SIEBOLD (1804–1885)
OVER THE NEXT 150 YEARS, SCIENTISTS CONTINUED TO USE THE MICROSCOPE
TO STUDY LIVING ORGANISMS SUCH AS PLANTS, INSECTS, AND MICROBES. BUT
BY THE EARLY 1800S, MOST BOTANISTS—SCIENTISTS WHO STUDY PLANTS—
WERE NOT USING MICROSCOPES. THEY WERE BUSY NAMING AND DESCRIBING
ENTIRE PLANTS. GERMAN BIOLOGIST MATTHIAS SCHLEIDEN (SHLY-DUN) WAS
AN EXCEPTION. ALTHOUGH HE WAS TRAINED AS A LAWYER, HE LEFT THE LAW TO
BECOME A PROFESSOR OF BOTANY. SCHLEIDEN PREFERRED TO USE A MICRO-
SCOPE TO STUDY PLANTS. (LOOK AT THE PLANT CELLS ON THE NEXT PAGE TO
SEE WHAT SCHLEIDEN MAY HAVE SEEN.) BASED ON HIS STUDY, HE SUGGESTED
IN 1838 THAT ALL PLANTS ARE MADE OF CELLS. THIS WAS A COMPLETELY NEW
IDEA: JUST AS A HOUSE COULD BE MADE UP ENTIRELY OF BRICKS, PLANTS WERE
MADE UP ENTIRELY OF CELLS!
SCHLEIDEN KNEW ANOTHER GERMAN BIOLOGY PROFESSOR, THEODOR
SCHWANN, WHO SPENT HIS TIME STUDYING ANIMALS. SCHWANN WAS PAR-
TICULARLY INTERESTED IN THE DIGESTIVE SYSTEM. IN 1839, ONE YEAR AFTER
SCHLEIDEN PROPOSED HIS THEORY, SCHWANN SUGGESTED THAT ANIMALS,
54 NGSPCC1
55 NGCCCO1
56 NGSPCC1
57 NGLS1A1
LEEUWENHOEK’S MICROSCOPE
WAS ONLY ABOUT 7 CM
(3 INCHES) LONG. THE SMALL
HOLE IN THE BOARD CONTAINED
THE MAGNIFYING LENS. THE
MATERIAL TO BE OBSERVED
WAS PLACED ON THE POINT IN
FRONT OF THE LENS.
ACTIVITY 4 THE HISTORY OF CELL THEORY
18 CELLS
AND NOT JUST PLANTS, WERE MADE UP OF CELLS. YOU CAN SEE ANIMAL CELLS IN
THE PHOTO BELOW. BECAUSE OF THEIR IDEAS, SCHLEIDEN AND SCHWANN ARE
CREDITED WITH DEVELOPING THE CELL THEORY: THE THEORY THAT ALL LIVING
ORGANISMS ARE MADE UP OF CELLS.58 59
OTHER SCIENTISTS BEGAN TO BUILD ON SCHLEIDEN’S AND SCHWANN’S IDEAS.
IN 1845, KARL THEODOR ERNST VON SIEBOLD (SEE-BOLD) SUGGESTED THAT
MICROBES WERE ALSO MADE UP OF CELLS—OR MORE SPECIFICALLY, ONE CELL
(SEE THE MICROBIAL CELL IN THE PHOTO BELOW). SIEBOLD BELIEVED THAT
ORGANISMS MADE UP OF MANY CELLS, LIKE ANIMALS, WERE BUILT OUT OF
SINGLE-CELLED MICROBES! WHILE SIEBOLD WAS WRONG ABOUT THIS IDEA, HE
WAS RIGHT IN STATING THAT MICROBES WERE LIVING CREATURES MADE UP OF THE
SAME MATERIAL AS ANIMALS AND PLANTS. 60
RUDOLF CARL VIRCHOW (1821–1902)
WHY IS SCHLEIDEN AND SCHWANN’S CELL THEORY IMPORTANT FOR UNDERSTAND-
ING INFECTIOUS DISEASES? THEIR WORK INFLUENCED RUDOLF CARL VIRCHOW
(VIR-KOH), A POLISH DOCTOR. HE HAD BEEN TREATING AND STUDYING ILL
PATIENTS FOR MANY YEARS. HE IS FAMOUS FOR SAYING IN THE 1850S, “ALL
CELLS ARISE FROM CELLS,” MEANING THAT CELLS REPRODUCE TO CREATE NEW CELLS.
HE WAS RIGHT. WHEN YOU SEE A NEW PLANT OR A BABY ANIMAL, YOU SEE A
MULTICELLULAR (MANY-CELLED) CREATURE. ALL LIVING ORGANISMS BEGIN AS A
SINGLE CELL. MOST MICROBES ARE MADE UP OF ONLY A SINGLE CELL, AS SIEBOLD
BELIEVED.
SINGLE-CELLED ORGANISMS, SUCH AS AMOEBA, ARE KNOWN AS UNICELLULAR.
THE CELLS OF MULTICELLULAR ORGANISMS, LIKE PEOPLE, CONTINUE TO DIVIDE AND
GROW. AN ADULT HUMAN BEING IS MADE UP OF ABOUT 10 TRILLION CELLS!61
58 NGLS1A1
59 NGPEL11
60 NGCCNS4
61 NGLS1A1
PLANTS ARE MADE UP OF CELLS,
LIKE THE PLANT CELLS SHOWN IN
THE PHOTO ABOVE.
ANIMALS ARE MADE UP OF CELLS,
LIKE THE SKIN CELLS IN THE PHOTO
ABOVE.
MANY MICROBES ARE MADE UP OF JUST ONE
CELL, LIKE THE MICROBE SHOWN IN THE PHOTO
ABOVE.
THE HISTORY OF CELL THEORY ACTIVITY 4
CELLS 19
VIRCHOW APPLIED HIS IDEAS TO DISEASE. HE KNEW THAT ALL CELLS GREW
FROM OTHER CELLS. HE THOUGHT THAT ALL DISEASES WERE CAUSED BY CELLS
THAT DID NOT WORK PROPERLY. HE BELIEVED THAT DISEASED CELLS CAME
FROM OTHER USUALLY HEALTHY CELLS OF THE SICK PERSON. VIRCHOW’S IDEAS
ABOUT DISEASE WERE NOT COMPLETELY CORRECT, ALTHOUGH THEY ARE CORRECT
FOR SOME DISEASES. HIS IDEAS WERE BASED ON HIS WORK WITH LEUKEMIA
(LOO-KEE-MEE-UH), WHICH IS A CANCER OF THE BLOOD. CANCER AND
CERTAIN OTHER DISEASES ARE CAUSED BY CELLS THAT NO LONGER FUNCTION AS
THEY SHOULD. IN THE CASE OF CANCER, THE CELLS TEND TO GROW WITHOUT
CONTROL. INFECTIOUS DISEASES ARE DIFFERENT, AS SCIENTISTS AFTER VIRCHOW
DISCOVERED.
LOUIS PASTEUR (1822–1895)
LOUIS PASTEUR (PASS-TUR), A FRENCH CHEMIST, BEGAN STUDYING
MICROBES IN 1864. HE WAS WORKING ON AN IMPORTANT BUSINESS IN
FRANCE: THE FERMENTATION OF WINE AND VINEGAR. HE NOTICED THAT CERTAIN
MICROBES COULD CAUSE FOOD AND DRINK TO SPOIL. PASTEUR DISCOVERED THAT
DIFFERENT MICROBES CAUSE DIFFERENT KINDS OF SPOILING, BUT HEAT CAN KILL
MANY OF THESE MICROBES. TODAY, BECAUSE OF HIS WORK, MILK IS HEATED TO
71°C FOR 15 SECONDS TO KILL THE MICROBE THAT CAUSES TUBERCULOSIS. USING
HEAT TO KILL MICROBES IS NOW KNOWN AS PASTEURIZATION, IN PASTEUR’S
HONOR. LOOK AT THE MILK CARTON SHOWN AT RIGHT. THE WORD PASTEURIZED
ON MILK SOLD IN STORES TELLS YOU THAT THE MILK IS SAFE TO DRINK.
EACH OF THESE MULTICELLULAR
ORGANISMS IS MADE UP OF
MILLIONS OF CELLS.
PASTEURIZATION KILLS
MICROBES THAT MAY BE
PRESENT IN MILK.
ACTIVITY 4 THE HISTORY OF CELL THEORY
20 CELLS
IN 1865, PASTEUR WAS ASKED TO HELP THE SILK INDUSTRY OF FRANCE, WHICH
WAS HAVING PROBLEMS WITH SILK PRODUCTION. SILK IS PRODUCED FROM
THREADS SPUN BY A WORM KNOWN AS THE SILKWORM. PASTEUR OBSERVED
A MICROBE THAT WAS INFECTING THE SILKWORMS AND THE LEAVES THEY ATE.
WHEN HE RECOMMENDED THAT THE INFECTED WORMS AND THEIR FOOD BE
DESTROYED, THE SILK INDUSTRY WAS SAVED.
PASTEUR KNEW THAT SOME DISEASES WERE INFECTIOUS. HE SUGGESTED THAT
MICROBES, WHICH HE REFERRED TO AS GERMS, COULD CAUSE INFECTIOUS DIS-
EASES AND WERE EASILY SPREAD BY PEOPLE. THIS IDEA IS THE BASIS OF THE
GERM THEORY OF DISEASE.
ROBERT KOCH (1843–1910)
SLOWLY, THE ROLE OF MICROBES IN CAUSING INFECTIOUS DISEASES BEGAN TO
BE ACCEPTED. BUT THERE WAS STILL MORE WORK TO DO. WHICH MICROBES
CAUSED WHICH DISEASES? IN 1876, ROBERT KOCH (KOKE), A GERMAN
DOCTOR, IDENTIFIED THE MICROBE THAT CAUSED ANTHRAX (AN-THRAKS), AN
INFECTIOUS DISEASE THAT WAS KILLING CATTLE. HE LATER WENT ON TO IDENTIFY
THE MICROBES THAT CAUSED TUBERCULOSIS AND CHOLERA (CAW-LE-RA).
AMAZINGLY, HE DID ALL OF HIS WORK IN THE FOUR-ROOM APARTMENT THAT HE
SHARED WITH HIS WIFE.
KOCH DEVELOPED A WAY TO PROVE THAT A SPECIFIC MICROBE CAUSED A
PARTICULAR DISEASE. IN THE CASE OF ANTHRAX, HE INJECTED HEALTHY MICE
WITH BLOOD TAKEN FROM FARM ANIMALS THAT HAD DIED OF ANTHRAX. HE
KOCH’S EXPERIMENT
INJECT WITH BLOOD FROM COW WITH
ANTHRAX
MICE DIE: ANTHRAX MICROBES CAN BE
ISOLATED FROM BLOOD OF INFECTED MICE
HEALTHY MICE
INJECT WITH HEALTHY COW BLOOD
MICE LIVE: NO ANTHRAX MICROBES IN
BLOOD OF HEALTHY MICE
HEALTHY MICE
THE HISTORY OF CELL THEORY ACTIVITY 4
CELLS 21
INJECTED ANOTHER GROUP OF HEALTHY MICE WITH
BLOOD TAKEN FROM HEALTHY FARM ANIMALS. ALL
OF THE MICE INJECTED WITH THE BLOOD FROM THE
INFECTED ANIMALS DIED OF ANTHRAX. NONE OF
THE OTHER GROUP OF MICE DEVELOPED ANTHRAX.
HE THEN SHOWED THAT HE COULD ISOLATE ANTHRAX
MICROBES ONLY FROM THE MICE THAT WERE
INJECTED WITH BLOOD FROM INFECTED ANIMALS.
HE DID NOT FIND ANTHRAX MICROBES IN THE
HEALTHY MICE. IN THIS WAY, KOCH WAS ABLE TO
PROVIDE SCIENTIFIC EVIDENCE THAT A SPECIFIC
ANTHRAX MICROBE CAUSED ANTHRAX.62
KOCH ALSO CREATED NEW WAYS TO GROW CULTURES
OF UNCONTAMINATED MICROBES. IN PARTICULAR,
HE DEVELOPED AGAR (AH-GUR), A GELATIN-LIKE
SUBSTANCE USED TO GROW MICROBE CULTURES ON A
SOLID SURFACE. AGAR IS STILL USED TODAY.
J. ROBIN WARREN (1937–)
BARRY MARSHALL (1951–)
BY THE 1970S, SCIENTISTS KNEW THAT MANY DISEASES WERE CAUSED BY
MICROBES. THEY KNEW THAT OTHER DISEASES, LIKE HEART DISEASE, WERE
CAUSED BY UNHEALTHY EATING, STRESS, NOT ENOUGH EXERCISE, AND GENETIC
FACTORS. FOR A LONG TIME, SCIENTISTS THOUGHT THAT ULCERS WERE CAUSED
BY CERTAIN FOODS AND STRESS. THEY DID NOT THINK THAT MICROBES COULD
CAUSE ULCERS BECAUSE THEY THOUGHT THE STOMACH WAS
TOO ACIDIC A PLACE FOR MICROBES TO LIVE. IN 1982, J.
ROBIN WARREN OF AUSTRALIA MADE AN IMPORTANT DISCOV-
ERY. WARREN WAS A PATHOLOGIST, A DOCTOR WHO LOOKS AT
TISSUES UNDER A MICROSCOPE TO DIAGNOSE DISEASE. WHEN
LOOKING AT SAMPLES OF PEOPLES’ STOMACHS, HE SAW
SMALL, CURVED BACTERIA IN MANY PATIENTS WITH ULCERS.
THIS BACTERIUM IS NOW CALLED HELICOBACTER PYLORI (H.
PYLORI). HE ALSO SAW THAT THE LINING OF THE STOMACH IN
ULCER PATIENTS WAS ALWAYS SWOLLEN IN THE AREA NEAR THE
BACTERIA.
BARRY MARSHALL WAS A DOCTOR AT THE SAME HOSPITAL AS
WARREN. THE TWO MEN DECIDED TO WORK TOGETHER TO
LEARN MORE ABOUT ULCERS. OVER THE NEXT FEW YEARS,
62 NGSPCE1
THE SUBSTANCE INSIDE THIS DISH IS KNOWN AS AGAR. MANY KINDS
OF MICROBES CAN GROW ON AGAR THAT HAS ADDED NUTRIENTS,
WHICH SERVES AS FOOD FOR THE MICROBES.
H. PYLORI BACTERIA IN THE DIGESTIVE SYSTEM
ACTIVITY 4 THE HISTORY OF CELL THEORY
22 CELLS
MARSHALL TRIED TO SHOW THAT H.
PYLORI COULD CAUSE ULCERS IN HEALTHY
ANIMALS. HE USED YOUNG PIGS FOR
HIS EXPERIMENTS, BUT THE PIGS DID
NOT DEVELOP ULCERS. PEOPLE DID NOT
BELIEVE HIS HYPOTHESIS THAT BACTERIA
CAUSED ULCERS BECAUSE HE COULD NOT
SHOW IT IN ANIMALS. AFTER YEARS OF NO
ONE BELIEVING HIM, MARSHALL DECIDED
TO GATHER EVIDENCE BY EXPERIMENTING
ON HIMSELF. HE USED AN ENDOSCOPE, A
LONG THIN TUBE WITH A CAMERA ON THE
END, TO TAKE PICTURES OF THE INSIDE
OF HIS STOMACH. HE THEN DRANK A WHOLE DISH OF H. PYLORI. AFTER A FEW
DAYS, MARSHALL STARTED VOMITING. HE WAS VERY TIRED, AND HIS WIFE AND
COLLEAGUES NOTICED THAT HIS BREATH SMELLED REALLY BAD. AFTER 10 DAYS,
HE HAD ANOTHER PICTURE TAKEN OF HIS STOMACH AND SAW THE SAME BAC-
TERIA THAT PEOPLE WITH ULCERS GET. THIS PROVIDED CONVINCING EVIDENCE
THAT H. PYLORI WAS THE CAUSE OF HIS SICKNESS.
OVER THE NEXT FEW YEARS, MARSHALL AND WARREN SHOWED THAT THE NEWLY
DISCOVERED BACTERIA GREW IN THE STOMACHS OF ALMOST ALL PEOPLE WITH
ULCERS. THEY ALSO SHOWED THAT ANTIBIOTICS CURED THESE PEOPLE. AS A
RESULT OF THEIR WORK, ULCERS BECAME A CURABLE DISEASE. MARSHALL AND
WARREN WERE AWARDED THE NOBEL PRIZE IN MEDICINE IN 2005.
EXTENSION
ROBERT HOOKE WAS AN AMAZING SCIENTIST. HIS SCIENTIFIC IDEAS IN THE
AREAS OF PHYSICS, PALEONTOLOGY, BIOLOGY, AND CHEMISTRY ARE STILL RELEVANT
TODAY. WHY DON’T WE KNOW MORE ABOUT HOOKE TODAY? SOME PEOPLE
BELIEVE IT COULD BE BECAUSE SIR ISAAC NEWTON WAS HIS ENEMY.
FIND OUT MORE ABOUT ROBERT HOOKE AND THE OTHER SCIENTISTS YOU READ
ABOUT IN THIS ACTIVITY. YOU CAN ALSO LEARN MORE ABOUT THE MILESTONES
IN THE DEVELOPMENT OF THE CELL THEORY AND THE MORE RECENT WORK OF
OTHER SCIENTISTS. BEGIN BY VISITING THE SEPUP THIRD EDITION FROM CELLS
TO ORGANISMS PAGE OF THE SEPUP WEBSITE AT WWW.SEPUPLHS.ORG/
MIDDLE/THIRD-EDITION.
BARRY MARSHALL AND J. ROBIN
WARREN ACCEPTING THE NOBEL
PRIZE IN MEDICINE
THE HISTORY OF CELL THEORY ACTIVITY 4
CELLS 23
MAGGOTS ARE NOW KNOWN TO BE A
JUVENILE STAGE OF FLIES.
THE THEORY OF SPONTANEOUS GENERATION
PASTEUR’S EXPERIMENT
VIRCHOW STATED THAT CELLS REPRODUCE TO CREATE
NEW CELLS. HOWEVER, MANY SCIENTISTS DID NOT
ACCEPT VIRCHOW’S IDEAS. THEY
BELIEVED IN SPONTANEOUS GENERA-
TION—THE IDEA THAT LIVING THINGS
GROW FROM NONLIVING THINGS.
FOR EXAMPLE, SOMEONE WHO
BELIEVED IN SPONTANEOUS GEN-
ERATION MIGHT THINK THAT PLANTS
GROW FROM SOIL. IF YOU WANTED TO
GROW A PLANT, YOU WOULD NEED
ONLY SOIL (NO SEEDS OR PLANT CUT-
TINGS). AFTER SOME TIME, A PLANT
WOULD SPONTANEOUSLY GROW OUT
OF THE SOIL. IT TOOK THE EXPERI-
MENTS OF MANY PEOPLE TO DISPROVE THE IDEA OF
SPONTANEOUS GENERATION.
IN 1668, AN ITALIAN DOCTOR NAMED FRANCESCO REDI
SET OUT TO SHOW THAT MAGGOTS GREW FROM EGGS LAID
BY FLIES. BECAUSE MAGGOTS WERE OFTEN FOUND IN
ROTTING MEAT, MANY PEOPLE BELIEVED THAT THEY JUST
APPEARED SPONTANEOUSLY. TO TEST HIS HYPOTHESIS,
HE SET UP SEVERAL FLASKS CONTAINING MEAT. SOME OF
THE FLASKS WERE OPEN TO THE AIR, SOME WERE SEALED
COMPLETELY, AND SOME WERE COVERED WITH GAUZE.
AS HE EXPECTED, MAGGOTS APPEARED ONLY IN THE
OPEN FLASKS IN WHICH THE FLIES COULD REACH THE
MEAT AND LAY THEIR EGGS.
IN 1767, ITALIAN PRIEST LAZZARO SPALLANZANI CON-
DUCTED EXPERIMENTS TO DISPROVE SPONTANEOUS
GENERATION. HE TIGHTLY SEALED SOME BOTTLES
THAT CONTAINED LIQUID AND THEN BOILED THEM
FOR MORE THAN 30 MINUTES. NOTHING GREW IN
THE BOTTLES. BUT BECAUSE HE HAD REMOVED THE
AIR FROM THE BOTTLES USING A VACUUM, MANY SCI-
ENTISTS BELIEVED THAT SPALLANZANI PROVED ONLY
THAT SPONTANEOUS GENERATION DID NOT OCCUR
WITHOUT AIR.
IT WAS NOT UNTIL NEARLY 100 YEARS LATER, IN 1859,
THAT FRENCH CHEMIST LOUIS PASTEUR CONDUCTED A
NOW-FAMOUS EXPERIMENT THAT
CONVINCED MOST PEOPLE. THE
FRENCH ACADEMY OF SCIENCES
HAD SPONSORED A CONTEST FOR
THE BEST EXPERIMENT TO EITHER
PROVE OR DISPROVE SPONTA-
NEOUS GENERATION. PASTEUR’S
WINNING EXPERIMENT WAS A
VARIATION OF THE METHOD USED BY
SPALLANZANI. HE PUT A MIXTURE
OF YEAST, SUGAR, AND WATER IN
SEVERAL GLASS FLASKS. HE THEN
HEATED THE NECKS OF THE FLASKS
TO BEND THEM INTO THE SHAPE OF AN “S” (SEE
THE FIGURE BELOW). AIR COULD ENTER THE FLASKS,
BUT AIRBORNE MICROBES COULD NOT. BECAUSE OF
GRAVITY, THEY WOULD LAND SOMEWHERE ALONG THE
NECK OF THE FLASKS. FINALLY, PASTEUR BOILED THE
FLASKS TO KILL ANY MICROBES THAT MIGHT ALREADY
EXIST IN THE MIXTURES. AS PASTEUR HAD EXPECTED,
NO MICROBES GREW IN THE FLASKS. WHEN PASTEUR
BROKE THE NECK OF A FLASK AND EXPOSED IT DIRECTLY
TO AIR, MICROBES GREW. PASTEUR PROVIDED CON-
VINCING EVIDENCE AGAINST THE IDEA THAT LIVING
ORGANISMS COME FROM NONLIVING THINGS.1 2
1 NGLS1A1
2 NGSPCE1
ACTIVITY 4 THE HISTORY OF CELL THEORY
24 CELLS
ANALYSIS
1. HOW DID THE CELL THEORY AND THE EVIDENCE THAT LED TO THE CELL
THEORY LEAD TO THE MODERN UNDERSTANDING OF THE ROLE OF GERMS IN
DISEASE? 63 64 65 66 67 68
2. EXPLAIN HOW SCIENTISTS USED EVIDENCE TO DISPROVE THE IDEA THAT
LIVING THINGS GROW FROM NONLIVING THINGS. 69 70 71 72
3. WHAT WAS THE ROLE OF TECHNOLOGY IN DISCOVERING THE CELL THEORY,
AND WHY WAS TECHNOLOGY IMPORTANT? 73 74 75 76
4. CREATE A LARGER VERSION OF THE VENN DIAGRAM SHOWN BELOW. RECORD
THE CHARACTERISTICS OF UNICELLULAR AND MULTICELLULAR ORGANISMS IN
THE CIRCLES WITH THOSE LABELS. IN THE SPACES THAT OVERLAP, RECORD
COMMON FEATURES.77 78
5. REVISIT THE ISSUE: TODAY WE KNOW THE CAUSES OF MANY INFECTIOUS
DISEASES, INCLUDING RELATIVELY NEW ONES SUCH AS EBOLA VIRUS AND
COVID-19 (NOVEL CORONAVIRUS). BUT THIS DOES NOT MEAN THAT
PEOPLE CAN ALWAYS STOP THE SPREAD OF THESE INFECTIOUS DISEASES,
AND NEW OUTBREAKS CONTINUE TO OCCUR. HOW COULD TECHNOLOGY HELP
SOLVE THIS PROBLEM? BRAINSTORM NEW TECHNOLOGY SOLUTIONS THAT
COULD HELP ADDRESS THIS ISSUE, AND DESCRIBE YOUR DESIGN(S). 79
6. REFLECTION: IMAGINE THAT EACH SCIENTIST IN THIS ACTIVITY WANTED TO
HIRE AN ASSISTANT. WHICH SCIENTIFIC TOPIC OR TOPICS WOULD YOU MOST
LIKE TO INVESTIGATE? WHY? 63 ELRS689
64 NGLS1A1 65 NGSPCE1
66 NGSPCC1
67 NGCCNS4
68 ELWH689
69 ELWH689
70 NGCCNS4
71 ELRS689
72 ELWH689
73 NGPEL11
74 NGCCCO1
75 NGCCNS5
76 NGSPCC1
77 NGSPCE1
78 NGCCSF1 | image tagged in memes,confession bear | made w/ Imgflip meme maker](http://i.imgflip.com/7zse7u.jpg)
