Presentation on theme: "Main Themes in Microbiology Chapter 1 Humans are outnumbered We have ~ 10 trillion cells in our body –We have 100 trillion foreign cells in/on our body!!"— Presentation transcript:
Spontaneous Generation The idea that life can arise from non-living matter –Aka abiogenesis Competing theory—biogenesis –Life can only arise from living things of a similar nature
How can we prove or disprove this hypothesis? Francesco Redi (1668) Hypothesis: Flies produce maggots on meat. Lay small eggs Set up a controlled experiment to test his hypothesis Found that by keeping flies away from meat, no maggots appear
Variables 1.Controlled variable: Jar, meat, location, temperature, time 2.Independent or Manipulative variable: Gauze covering the meat jars 3.Dependant (responding) variable: Whether maggots appear
John Needham – 1745 Hypothesis: spontaneous generation occurs under the right conditions –Boiled chicken broth and then sealed flask (thought heat would kill) –“Animalcules” swarmed after a few days –Therefore, he felt his hypothesis was right.
What was wrong with Needham’s hypothesis? Was it flawed? He assumed all the animalcules would be killed by heat
Louis Jablot Hypothesis: even microscopic organisms must have parents Boiled hay infusions very similar to Needham’s work However, his uncovered WAS contaminated with growth
Lazzaro Spallanzani 1776 Attempted to disprove Needham’s work. Took 4 flasks with broth in them –Left open – went cloudy –Sealed but not boiled – went cloudy –Boiled but left open – went cloudy –Sealed then boiled – stayed clear Microbes were not found in this one but in all the other ones
What would have been Spallanzani’s hypothesis? Microorganisms form not from air but from other microorganisms. When broth was boiled and then sealed, no air could get in for organisms to reproduce.
What was wrong with what Spallanzani assumed? No air
Louis Pasteur - 1859 Tested Spallanzani’s work by using a curved neck flask to prevent microbes from entering flask but would let air in Boiled broth of control and experimental flasks. Result: No growth in curved neck flask. Microbes collecting in bend
Pasteur’s broth in the curved necked flask stayed sterile for years until he tilted it and the airflow carried the microbes into the broth
Conclusion Contamination is due to microbes in the air. Spontaneous generation theory died here!!
John Tyndall Heated hay infusions for various times. Found 2 kinds of bacteria – 1. Those readily killed by heating 2. Heat resistant forms (endospores) **Between 1875 – 1918, most of the disease-causing bacteria were identified.
The Microscope Leeuwenhoek looked at a drop of water and saw moving things Called them “animacules” Bacteria and protozoa
The Pillar of Science: The scientific method Origin in the 1600s…enough of the superstition!!
The Scientific Method 1.Ask a question Do some research 2.Propose a hypothesis 3.Conduct a controlled experiment 4.Collect data and make observations 5.Analyze data 6.Make a conclusion 7.Possibly, write a theory
Scientific method NEEDS a testable hypothesis Use the deductive approach ▫If…then (because) Test, test, and retest that hypothesis!
Do you know where bees come from? Recipe for Bees 1.Kill a bull during the first thaw of winter 2.Build a shed 3.Place the dead bull on branches and herbs inside the shed 4.Wait for summer. The decaying body of the bull produces bees Words from a Roman poet about 2000 years ago
Know the jargon Hypothesis- tentative explanation for what has been observed Theory- very well supported idea Many hypotheses and experiments NOT A “FACT Law- principle of science Super accurate
Germ theory of disease Louis Pasteur ◦ Human diseases could arise from infection Robert Koch ◦ Koch’s Postulates Verified germ theory Showed anthrax caused by bacterium
Taxonomy- formal system for organizing, classifying, and naming organisms Carl von Linnie Aka Carolus Linnaeus Standardized Keeps names short and consistent Binomial system of nomenclature
a two name system for writing scientific names. The genus name is written first (always Capitalized). The species name is written second (never capitalized). Both words are italicized if typed or underlined if hand written. Example: Smith john (print) Smith john (written) Felis concolor or F. concolor Which is the genus? The species? Binomial Nomenclature
The major classification levels, from most general to most specific (several of these have subdivisions) A group at any level is a taxon.
Kingdoms are divided into groups called phyla Phyla are subdivided into classes Classes are subdivided into orders Orders are subdivided into families Families are divided into genera Genera contain closely related species Species is unique Categories within Kingdoms