Adapted from another PP found on Internet

1. History of Cell
Discovery

2. Daily Question:
Brainstorm: What do you think of when you think of the
word cell?
Use a circle map to brainstorm

3. 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
*Robert Hooke in England

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

5. Leeuwenhoek’s
drawings of
“animalcules” set off a
flurry of amateur and
sometimes ridiculous
claims, such as:
- pondwater
animalcules causing
madness!

6. *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.

7. Pause
Take two minutes to summarize your
notes into your own words.

8. *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.

9. People throughout the
Middle Ages believed
that mice could be
“created”
spontaneously by
putting grain in dark,
quiet place and leaving
it for a few weeks.

10. The discovery of
cells only confused
people more- If
cells are alive,
then where do
they come from?
Can these
almost invisible
things appear
spontaneously
from the air?

11. *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

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

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

14. 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”

15. Pause
Take two minutes to summarize your
notes into your own words.

16. *Lazzaro Spallanzani
*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

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

18. 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.

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

20. 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.

21. The curved neck allows air in but traps
bacteria-carrying dust and dirt particles

22. *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.

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

24. *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.

25. 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...

26. The Cell Theory
The cell theory has three parts:
All living things are composed of one
or more cells
Cells are the basic unit of structure
and organization of all living things
Cells can only come from pre-existing
cells

27. *The cell theory
1. *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.

28. 2. *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

29. *3. 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

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

31. And now…
Use Google images (select
photos) to find photographs
of cells.
Write a description of three
cells that you see on your
paper…

32. Complete the
Study Guide for ch 7.1
If you finish early you may work on
credit Option A