Part One: Spontaneous Generation and Biogenesis: A Brief History Part Two: Microscopy

1. Part One:Spontaneous Generation and Biogenesis: A Brief HistoryPart Two:Microscopy

2. The First Observations • In 1665, ________ ________ reported that living things were composed of little boxes or cells. • 1673-1723, _______ ____ _______________– first to describe live microorganisms that he observed in teeth scrapings and pond water

3. The Debate Over Spontaneous Generation • The hypothesis that living organisms arise from nonliving matter is called _______________ _________________. According to spontaneous generation, a “_________ _______” forms life. • The alternative hypothesis, that the living organisms arise from preexisting life, is called ______________. • In 1858, Rudolf ____________ said that cells arise from preexisting cells. • Cell Theory: All living things are composed of _________ and come from preexisting ___________.

4. Experimental Design • Beginning in 1668, experiments were conducted to either prove or disprove spon gen. • But before we get into that, let’s talk about experimental design. Some terms: • Control – something that is used as a constant and unchanging standard of _______________ in an experiment • Variable – factor, trait, condition, etc that ___________in an experiment • Manipulated/Independent variable – variable that is changed (manipulated) by the scientist; only one of these in an experiment • Responding/Dependent variable – variable that responds to and depends upon the ___________________ variable • Experimental group - group in an experiment that receives the _____________________ variable • Control group – group in an experiment that does NOT receive the _____________________ variable

5. Experimental Design Example • Chemists working for LiveLonger Pharmaceuticals believe that they have developed a drug that will lengthen human life. This potential drug needs to be tested before LiveLonger can apply for a patent from the Food and Drug Administration for production of their life-lengthening drug. • Research scientists from LiveLonger test the drug as follows: • 5,000 individuals involved; 2500 60-year-old non-smoking men and 2500 60-year-old non-smoking women • 50% are given a pill containing the drug; 50% are given a placebo • Study conducted over a five-year period • Controls? • Manipulated variable? • Responding variable? • Experimental group? • Control group? Experimental design (2:39)

6. Experiment #1 • 1668: Francesco Redi (biogenesis) placed decaying meat in nine jars then made these observations:

7. Redi’s Experiment

8. Experiment #2 • 1745: John Needham (spon gen) put boiled nutrient broth into flasks.

9. Experiment #3 • 1767: Lazzaro Spallanzani (biogenesis) boiled nutrient solutions in sealed flasks.

10. Needham’s and Spallanzani’s Experiments (sort of)

11. Experiment #4 • 1861: Louis Pasteur (biogenesis) demonstrated that microorganisms are present in the air.

12. Pasteur Settles the Debate: Experiment #5 • 1864-1865: Pasteur boiled broth in open swan-necked flasks and let the flasks sit for a __________. No __________ grew in the broth. He then broke off the necks and within a few hours the flasks were teeming with _________________.

13. Part Two: Microscopy History of the Microscope (4:40)

14. Microscopy: The Instruments • A ________ __________ has only one lens. • ____ _______________ was obsessed with lens grinding. He ground single lenses that could magnify _____x; they were by far the ________ in the world at that time. Leeuwenhoek Video (2:00)

15. Microscopy: The Instruments • 1595: First ____________ microscope; made by Hans and Zaccharias Janssen • _____ lenses: one at the top and one at the bottom • Poor __________ and low __________, but it paved the way

16. Microscopy: The Instruments • In a ______________ microscope the image from the objective lens is ______________ again by the ocular lens. • Total magnification =_____ lens  _____ lens

17. Microscopy: Resolution • _______________ is the ability of the lenses to distinguish two points. • A microscope with a resolving power of 4nm can distinguish between two points ≥ 4nm. If less than 4nm apart, then the two points appear as one. • The better the ___________, the finer the detail. • Visible light, because of its long _____________, limits light microscopes to _____x.

18. Electron Microscopy • Uses _________ instead of ________. • The shorter ____________ of electrons gives far greater ____________ than visible or UV light and can therefore show the smallest objects known.

19. Transmission Electron Microscopy (TEM) • Ultrathin sections of specimens must be used. • Electrons pass through specimen, then an ____________________ lens to a screen or film. • Internal chamber is a ___________. How a TEM works (1:48)

20. Transmission Electron Microscopy (TEM) • 10,000-100,000 (5,000,000x max) • Resolution 2.5 nm • Great for examining viruses and internal cellular structures

21. Scanning Electron Microscopy (SEM) • An electron gun produces a beam of ___________ that _________ the surface of a whole specimen.

22. Scanning Electron Microscopy (SEM) • 100-10,000x (300,000x max) • Resolution 20 nm • Great for examining surface features

23. Scanned-Probe Microscopy Individual silicon atoms • Scanning tunneling microscope uses a metal __________ to __________ the surface of a specimen. • Produces an image that reveals the ridges and depressions of individual _________ • Resolution: 1/100 of an atom!! • Most _____________ microscope on earth! “Molecular Man” Image made from scanning 28 CO molecules on platinum

24. Scanning Tunneling Microscope From the simple…. (couple of thousand $$) to the complex! (hundreds of thousands)