Redi’s Experiments
When decaying meat was kept
isolated from flies, maggots
never developed
* Meat exposed to flies was soon
infested
* More complex animals
developed through biogenesis
Needham’s Experiments
- Scientists did not believe larger animals could arise spontaneously,
but did believe microbes could - Needham’s experiments with beef gravy and infusions of plant
material reinforced this idea - Boiled beef gravy and infusions of plant material in vials and then
sealed them with corks - Vials were cloudy and contained “microscopical animals of most dimensions”
- Must be a “life force” that causes inanimate matter to spontaneously
come to life - Boiling killed microorganisms
- Microorganisms could develop in the infusions
Spallanzani’s Experiments
- Boiled infusions and then sealed the vials
- Infusions remained clear unless he broke the seal and exposed the
infusions to air - Concluded that
- Needham had either failed to heat vials sufficiently to kill all microbes or had
not sealed vials tightly enough - Microorganisms exist in air and can contaminate experiments
- Spontaneous generation of microorganisms does not occur
- Critics said sealed vials did not allow enough air for organisms to
survive and that prolonged heating destroyed “life force”
Pasteur’s Experiments
- “Never will spontaneous
generation recover from
the mortal blow of this
simple experiment” - Microbes in the liquid
were the progeny of
microbes that had been
on the dust particles in
the air
What Causes Fermentation?
- Pasteur discovered that anaerobic bacteria fermented grape juice
into acids that then spoiled the wine - Pasteurization – gently heating grape juice to kill the bacteria without
altering its qualities; then inoculated with yeast - Yeast fermented the grape juice into alcohol
- Began the field in industrial microbiology (microbes used in
manufacturing products)
Viruses
not prokaryotic or eukaryotic
much smaller and simpiler
What Causes Disease?
- Pasteur’s discovery that bacteria were responsible for spoiling wine
led him to hypothesize that microorganisms were responsible for
causing disease - Germ Theory of Disease
- Now only applies to infectious diseases
photosynthetic microbes do —- of all photosyntheis on earth
> 50%
great oxygen event
cynanobacteria began photosynthesizing
Bacteria and archaea
PROKARYOTIC
lack membrabne bound organelles
have cell walls that contain peptidoglycan
reproduce asexually
are much smaller than eukaryotes
ARCHAEA are found in extreme environments
only a FEW bacteria are kn own to cause disease in humans
Fungi
EUKARYOTIC
have cell walls but no peptidoglycan
there are molds (multicellular, hypahe, sexual/aesexual) and yeasts (unicellular, aesexually budding, some sexual spores)
PROTOZOA
EUKARYOTIC
single celled
most aesexual
some have complex life cycles that include more than one host
most are capable of locomotion (pseudopodia, cilia, flagella)
algae
EUKARYOTIC
multi or uni
photosynthetic!!!! (make own food from C02 and water using energy from sunlight)
very important for global ecology
