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Characteristics of Life

1. Motility
2. Growth
3. Metabolism- consists of both anabolic and catabolic processes
4. Irritability-ability to respond to a stimulus
5. Reproduction
6. Molecular Complexity
7. Organization
8. Adaptation
9. Differentiation



genetic potential of living organisms to survive to changes in the environment



two biological model systems have been used to help study this process.
a. Process by which B lymphocytes (B cells) differentiate into plasma cells to produce antibodies.
b. Process by which a vegetative bacterial cell differentiates into a spore.


two components to Cell Theory

The first part was established in 1838-1839 by Schleiden
(botanist) and Schwann (zoologist). Even the most complex living organisms are composed of
elementary parts that are repeated over and over again. These parts are called cells


two components to Cell Theory

The second part was added by Rudolf Virchow in 1858. This was the theory of Biogenesis. Biogenesis states that living cells arise from pre-existing living cells. A genetic continuity of life. Biogenesis set aside the notion that
some forms of life could arise spontaneously from nonliving matter. This controversy between spontaneous generation and biogenesis had gone on for hundreds of years.


Major contributors and historical figures

Robert Hooke
Anton van Leeuwenhoek
Francesco Redi
John Needham
Lazzaro Spallanzani
Louis Pasteur


Robert Hooke (1665)

used the word cells to describe the holes in cork.


Anton van Leeuwenhoek (1674)

- father of Microbiology. First to report his
observations. He described “animalcules” from teeth scrapings. The resolution of his primitive
microscope/lens system was approximately 1.45 micrometers.


The battle over the existence of spontaneous generation can be traced back to

to the ancient Greeks and Romans. Virgil (70 – 19 B.C.)


Romans. Virgil (70 – 19 B.C.)

) a Roman epic poet wrote a treatise on the artificial propagation of bees.
He believed that bees came from honey.


Francesco Redi (1668)

He was skeptical about spontaneous generation and set-up an experiment that showed that that worms (larvae) on meat actually came from flies that landed on the meat and laid eggs. The worms did not arise spontaneously from meat.


John Needham (1745)

looked at infusions (soups, broths) through microscopes.
When spoiled, he saw many microorganisms. He heated these spoiled infusions to kill the growth and then placed a cork on these flasks. Since organisms then grew, he claimed that spontaneous generation


Lazzaro Spallanzani

Heated sealed flasks with non porous corks. These flasks did not result in microbial growth. Therefore, he did not believe in spontaneous generation. Needham responded that Spallanzani had not allowed “vital forces” to enter flask, and that is why spontaneous generation did not work.


Louis Pasteur (1861)

using his famous long necked flasks that were bent into S-shaped curves, presented a paper in Paris that completely ended this controversy. Yeast infusions were heated to kill cells. The “vitalists” were satisfied because the flasks were open. Nothing grew. No spontaneous


John Tyndall

developed a process known as tyndallization. By alternately heating and incubating hay infusions both vegetative cells and spores would be destroyed. Pasteur’s apparatus could now be used with hay infusions.


Other scientists attempted to duplicate Pasteur’s work with his S flasks
What did they do?

they used hay infusions rather than yeast infusions. These experiments did not work. There was growth following the heating process. Why? Hay infusions had heat resistant cells known as spores.


Germ Theory of Disease

Girolamo Fracastoro
Agostino Bassi
Louis Pasteur
Joseph Lister
Robert Koch


Girolamo Fracastoro (1546)

described the idea of ‘contagion”, something passed on
from one person to another. This led to quarantines. No one knew what was passed along to
make people sick. Some believed it was miasmata, poisonous gasses from decomposing bodies.


Agostino Bassi (1836)

studied fungal disease in silkworms. He connected the fungi with disease. First association with microorganism and disease.


Louis Pasteur (1865)

Studied Pebrine Disease. Another disease of silkworms. This disease was caused by a protozoan.


Joseph Lister (1867)

- Introduced antiseptic principles in surgery. In 1878 he established a technique for creating pure cultures using serial dilutions. Pure cultures were critical for being able to connect a particular microorganism with a particular disease. Serial dilutions can also be used to reduce the number of cells/ml for purposes of counting concentrated suspensions of bacteria.


Robert Koch (1876)

established a protocol (Koch’s postulates-Ch 14) for directly relating a specific microbe to a specific disease. He determined that Bacillus anthracis was the etiologic
agent of anthrax.


chicken cholera & Pasteur

Pasteur publically demonstrated that Pasteurella multocida caused chicken cholera. An error in the
demo made Pasteur think about immunity. Back in 1798 Edward Jenner used cowpox vaccine to
prevent smallpox. Jenner is credited with using the first vaccine. (Louis Pasteur coined the term vaccine
nearly 100 years later, vacca for cow).