INTRO TO EVOLUTION

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

Miller Urey

Experiment/Recreation

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