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