Unit 1: Chapter 1
Matter and Energy For Life
Development of the Cell Theory
 For
hundreds of years
a debate raged
amongst scientists,
about the origin of
living things.
Onion skin cells
 The
debate centered
around two theories:
1. Abiogenesis
2. Biogenesis
Paramecium
What is abiogenesis?

Abiogenesis is the idea that living
organisms can arise from non-living matter.

It is also called Spontaneous Generation
 Thomas Huxley first used
the term abiogenesis

Examples of abiogenesis:
◦ Appearances of mushrooms on logs
◦ Maggots forming on rotting meat
◦ Frogs and salamanders suddenly appearing on
or in mud
What scientists supported abiogenesis?

Aristotle (384-322 B.C.E.) classifies all
organisms into 2 kingdoms: plants and
animals.

He believed all living organisms can only
arise from non-living matter.
John Needham (1713-1781)
 He believed microorganisms appeared in a
sterilized flask of meat broth

He placed broth into a bottle, heated the
bottle to kill anything inside, then sealed it.

Days later, he reported the presence of life in
the broth and announced that life had been
created from nonlife.
◦ What actually happened?
 He did not heat the broth long enough to kill all the
microbes. Therefore, after a few days, microbes (ex: mold)
appeared in the bottle.
What is biogenesis?

Biogenesis is the idea that living
organisms can only come from other
living things.
What scientists supported biogenesis?
Francesco Redi (1629-1697)
 He made the first serious attack on
abiogenesis. During this time, people
believed maggots just appeared on rotting
meat.
 Redi believed that maggots actually came
from fly eggs, which are not visible to the
eye. He performed an experiment to show
that maggots will not appear on rotting meat
if flies are kept away.
Francesco Redi’s Experiment
◦ See page 8 in textbook
http://www.sumanasinc.com/webcontent/an
imations/content/scientificmethod.html
Spallanzani (1729-1799)

He was skeptical of Needham’s
experiment, so he did his own

He boiled the broth for a longer period of
time and he kept one of the bottles sealed.

No life appeared in the sealed bottle
Louis Pasteur (1822-1895)
 He ended the debate on abiogenesis

He designed an experiment to prove
microbes do not just appear in sterilized
meat broth.

Instead, these microbes actually come from
the air.
http://bcs.whfreeman.com/thelifewire/conte
nt/chp03/0302003.html
http://www.sumanasinc.com/webcontent/animations/
content/scientificmethod.html
Paradigm Shift

As a result of the debate over abiogenesis
and biogenesis there was a change in the
way that science viewed the “origins of
life”.
The cell theory was developed
Cell Theory Video
http://www.youtube.com/watch?v=dscY_2
QQbKU

Other Scientists that contributed to
the development of the cell theory:

Robert Hooke (1665) using a primitive set
of lenses to form a simple microscope,
observes “empty room like apartments” in
samples of once living tree bark. Hooke
names these compartments cells.

Anton van Leeuwenhoek (1667)
designs his own microscopes that are far
more powerful than any of the primitive
forms at the time. Over the next number
of years Leeuwenhoek writes extensively
about his observations of tiny living
organisms.

Robert Brown (1831) observes a darker
region in all cells near the centre and
named it the nucleus.

Mathias Jacob Schleiden (1838) writes,
“All plants are made of cells”.

Theodor Schwann (1839) writes “All
animals are made up of cells” and further
goes on to state that “Cells are organisms
and entire animals and plants are
collectives of these organisms”.

Alexander Carl Henrich Braun (1845)
wrote “the cell is the basic unit of life”.

Rudolph Virchow (1858) formulates the
points of the cell theory.
The wacky history of cell theory – by
Lauren Royal-Woods
http://ed.ted.com/lessons/the-wackyhistory-of-cell-theory
(*Important: please write!)
Cell Theory
1.
2.
3.
4.
All living organisms are composed of one
or more cells
Cells are the basic units of structure and
function in all organisms
All cells are derived (come from) preexisting cells (biogenesis)
In a multicellular organism, the activity of
the entire organism depends on the total
activity of its independent cells.
The cell theory song
 http://www.youtube.com/watch?v=KuJqqi
ATlqw
Work:
Review worksheet/handout on Scientists
 In class assignment on Scientists
