EVIDENCE OF EVOLUTION
SPONTANEOUS GENERATION
& EARLY LIFE
SPONTANEOUS GENERATION

Definition: hypothesis stating that life
could arise from nonliving matter

Believed that nonliving matter contained a
life-giving property called active
principle that enabled it to produce
living things all the time
FRANCISCO REDI


Noted that maggots
had come from eggs
laid by flies that
had entered the
open jars
Provided evidence
that life only comes
from life—known as
biogenesis
JOHN NEEDHAM



Disputed Redi’s
experiment by
boiling water to
kill bacteria
Broth eventually
became clouded
with bacteria
Problem—broth
not boiled long
enough
LAZZARO SPALLANZINI



Broiled broth
longer to kill all
active bacteria
Sealed flask
remained free of
bacteria
Once open to air—
bacteria grew
LOUIS PASTEUR
WHERE DID THE
1ST CELL COME FROM?

Cell theory states—all cells come from
preexisting cells

The heterotrophic hypothesis was
developed to explain how the 1st primitive
life forms came into existence
IMPORTANT TERMS
Heterotrophs: organisms that must
ingest preformed organic molecules
Autotrophs: organisms that can
manufacture their own food
Aerobic Respiration: respiration
requiring oxygen to produce energy
Anaerobic Respiration: respiration that
does not require oxygen to produce energy
CONDITIONS OF EARLY EARTH

Atmosphere: ammonia (NH3), methane
(CH4), water (H2O), and hydrogen (H2)

Energy: lightning, UV light, x-rays

Primitive Sea: a “hot, thin soup”
composed of amino acids, proteins,
carbohydrates, nucleotides
EARLY ORGANISMS

Organisms required to carry out
anaerobic respiration due to the absence
of O2 in atmosphere

Organisms were heterotrophs because
there was an absence of CO2 in the
atmosphere to make their own food
FORMATION OF
ORGANIC COMPOUNDS

Atmosphere is composed of inorganic
compounds

Energy—UV light, lightning, volcanic
activity—broke the bonds of those gases
creating the “hot, thin soup” of organic
compounds
ARRIVAL OF AUTOTROPHS

Heterotrophs ingested components of the
primitive seas, releasing CO2 into the
atmosphere
Autotrophs evolve as a result of the following:
 Food supply for heterotrophs decreased over
time
 Both CO2 and H2O are available to carry out
photosynthesis
 O2 became available, so aerobic organisms
evolved as well