EVOLUTION
1. Defined as a change in a species over a period
of time
2. Change in the allele frequency of a gene pool
EARLY EARTH
1. Based on radiometric dating of rocks – the
earth is approximately 4.5 billion years old
2. Hypothesized early conditions
Hot, volcanic activity, no free O2 water vapor, CO2,
H2, N2, ammonia and methane (CH4)
EARLY EARTH
3. About 4.4 billion years ago
Great cooling period proposed timeframe in
oceans is approximately 3.9 bya
EARLY EARTH
4. Oparin’s Hypothesis
a) Early rain + lightning created oceans where first
life was formed from simple organic compounds
b) 3.5 mya in the “primordial soup” (oceans), organic
compounds came together to form protocells
(precursor to the first cell) which
would later be known as
prokaryotic cells
EARLY EARTH
5) Organic from inorganic ?
a) Stanley Miller and Harold Urey sought to recreate
Oparin’s hypothesis in a lab
EARLY EARTH
b) Setup
I. Sealed gases (water, methane, ammonia,
hydrogen) inside a closed loop
II. Electrodes – simulate lightning
III. Chambers to heat and cool liquids
c) Results – liquids contained amino acids,
sugars, lipids building blocks
PROGRESSION OF LIFE FORMS
1) Anaerobic (no oxygen), prokaryotic, heterotrophic organisms photosynthetic (ex. Cyanobacteria) prokaryotes eukaryotic multicellular
2) Endosymbiont theory
Large prokaryotic cells took up smaller cells that performed cell respiration and photosynthesis to create eukaryotic cells
Mitochondria has it’s own DNA and is thought to have once been an independent organism
EARLY THEORIES ABOUT LIFE
1) Abiogenesis (spontaneous generation) =
nonliving materials can produce life
2) Biogenesis = only living organisms can
produce life. Proved by 2 scientists
EARLY THEORIES ABOUT LIFE
a) Francesco Redi (1600s)
I. Placed decaying meat in 4 jars
I. 2 covered and 2 uncovered
II. Over time – maggots and flies filled only the
uncovered jars
III. Conclusion – meat does NOT produce life
EARLY THEORIES ABOUT LIFE
b) Louis Pasteur (1800s)
I. Filled flasks with broth that was boiled (killing all
existing microorganisms )
II. Flasks had S-shaped necks to allow air in but
prevented microorgs from entering, stuck in the
neck with dust
EARLY THEORIES ABOUT LIFE
III. Nothing grew in the flask
IV. Pasteur tilted the flask so that microorgs
could not come into contact with the broth –
microorgs soon began to grow
V. Conclusion: Microorgs come from other
microorgs and not the broth