Cells: How their discovery led to the cell theory

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Cells: How their discovery led to the cell theory

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1. Cells: How their discovery led to the cell theory http://www.usoe.k12.ut.us/CURR/Science/sciber00/7th/cells/sciber/intro.htm check out this website for activiteshttp://www.usoe.k12.ut.us/CURR/Science/sciber00/7th/cells/sciber/intro.htm check out this website for activites

2. History Cells were unknown until the discovery of microscopes in the 1650’s two scientists working independently built the first microscopes Anton von Leeuwenhoek in Holland 1676 Robert Hooke in England 1665

3. Hooke Studied cork - a kind of tree bark named the structures he saw “cells” because they reminded him of the small rooms monks slept in.

4. Leeuwenhoek Studied pondwater, and sour milk, named moving organisms “animalcules” scared people and caused a sensation

9. The Cell Theory The cell theory has three parts: All living things contain at least one cell Cells are the smallest living units of matter Cells can only come from pre-existing cells

10. The cell theory-a closer look All living things contain at least one cell Many scientists working after Hooke and Leeuwenhoek observed different plants and animals Each of them noted that no matter what they observed, if it was alive it had cells.

11. Cells are the smallest living units of matter scientists quickly realized that when cells were dissected or broken open they died This meant that whatever “life” is, it is something that happens inside cells

12. Cells can only come from pre-existing cells does not answer the question of where the first cell came from or how it came to be. has not been disproved yet- no scientist has ever built a living cell from nonliving organic molecules

13. Spontaneous Generation From pre-historic times to about 1850, most people believed that under the right conditions, living things could spontaneously appear from non-living material.

16. Francesco Redi Born 1626 in Italy First to challenge the idea of spontaneous generation Did not accept the common belief that flies magically appeared from rotting meat

17. Redi’s Experiment IV=cover DV=presence of flies Hypothesis: If a jar containing rotting meat is covered, then it will produce no flies

18. Redi’s Conclusions Flies lay eggs, which grow into maggots, which metamorphose into flies If flies can’t lay eggs, then no new flies can grow

19. Objections to Redi Many people rejected Redi’s claim that flies do not spontaneously generate Their reasoning: “sealing the jar closed prevented a magical essence from entering the rotting meat and brining it to life” “Scientists seek only to challenge belief systems and stir things up”

20. 1729. Italian Believed microbes that spoil food come from the air and can be killed by boiling IV= air, DV=food spoilage Hypothesis: If air is allowed to reach food, then microbes will get in and cause it to spoil Lazzaro Spallanzani

21. Spallanzani’s Experiment Flask 1: boiled broth, open Flask 2: boiled broth, sealed shut Results Flask 1 spoiled Flask 2 did not spoil

22. Objections to Spallanzani Sealing the flask shut blocked the entrance of a magical life force in the air from getting to the broth. Since few people had seen these microbes, few people believed him.

23. Louis Pasteur 1822. France Supported that spontaneous generation is a myth Invented pasteurization (sterilization by heat)

24. Pasteur’s Experiment An improvement on Spallanzani’s work Used special “swan-neck flasks” that allowed air in but kept bacteria out IV= bacteria, DV=spoiling broth Hypothesis; If boiled broth is kept free of bacteria, then it will not spoil even if air can reach it.

26. Spontaneous generation is dead! Redi didn’t believe in it, and did an experiment using flies Spallanzani didn’t believe in it, and experimented with broth Pasteur disproved it conclusively with his open-air yet spoilage free flasks.

27. Life from dead stuff= 0 Biogenesis = 3 Experimental method wins out over superstition the cell theory takes hold among ordinary people

28. Pasteur is the father of modern microbiology supported the last part of the cell theory: cells only come from pre-existing cells identified yeasts as the microbes that change grape juice into wine showed that heat can be used to sterilize foods and preserve them in sealed glass containers, and later cans.

29. Finally... in the late 1870’s, doctors start to wash their hands and instruments before operating...some even start wearing gloves! Joseph Lister’s wacky idea that antiseptics kill germs catches on...

30. The cell theory is one of the most important theories in biology. All living things contain at least one cell Cells are the smallest living units of matter Cells can only come from pre-existing cells

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