Download How Did Life Begin?

How Did Life Begin?
Chapter 12, Section 1
Biology
Mrs. James
The Age of Earth
 Earth began 4.5
billion years ago
 Was fiery ball of
molten rock
 Water vapor
condensed into
oceans
 Scientists believe life
began in the oceans
Measuring Earth’s Age
 Radiometric dating –
estimating age by
measuring radioactive
isotopes
 Radioisotopes –
unstable isotopes that
give off energy
 These breakdown and
end in decay and
stable isotopes
Measuring Earth’s Age
 Half-life – the time it
takes for a given
amount of
radioisotopes to
decay
 Scientists can
measure half-lifes
which can tell them
how old rocks &
fossils are
Formation of the Basic Chemicals
of Life
 Scientists believe that
the chemicals of life
were formed when
non-living particles
reacted chemically
 They were energized
by the sun and
volcanic heat
 Simple molecules
then formed more
complex molecules
The “Primordial Soup” Model
 Thought up by A. I.
Oparin from Russia
 & J.B.S. Haldane
from Britain
 They thought the
ocean was full of lots
of different organic
molecules
 Like a soup full of
meat and veggies
The “Primordial Soup” Model
 The molecules
formed spontaneously
by:
 Solar radiation
 Volcanic eruptions
 Lightning
They also believed that
early earth lacked
oxygen
Instead it had nitrogen
gases
The “Primordial Soup” Model
 This model was
tested in 1953
 They set up their
“theory” in a lab
 They found chemicals
such as:
 Amino acids
 Fatty acids
 Hydrocarbon
molecules
The Bubble Model
 Louis Lerman thought
that organic
chemicals were
formed in bubbles on
the ocean’s surface
 This is called “The
Bubble Model”
The Bubble Model
 Step 1
 Ammonia, methane &
other gases result
from eruptions
 They become trapped
in bubbles
The Bubble Model
 Step 2
 The chemicals trapped
in bubbles were
protected from
ultraviolet radiation
 Chemical reactions
take place much faster
in bubbles
 Because they are
concentrated
The Bubble Model
 Step 3
 Bubbles rose to the
surface and burst
 This released simple
organic molecules into
the air
The Bubble Model
 Step 4
 They were carried up
by winds
 Exposed to ultraviolet
radiation and lightning
 This provided energy
for further reactions
The Bubble Model
 Step 5
 More complex organic
molecules fell into the
ocean with rain
 This started the cycle
all over again
Precursors of the First Cells
 Most scientists agree
that basic molecules
formed spontaneously
 In labs scientists are
not able to form DNA
or RNA
 Small strands can be
formed in water
Microspheres and Coacervates
 Lipids, which make up
amino acids, tend to
gather in water
 Think about when you
mix oil and water
together
 Microspheres – short
chains of amino acids
that gather in tiny
droplets
Microspheres and Coacervates
 Coacervates are like
microspheres but
formed of amino acids
and sugars
 Microspheres led to
cellular organization
Origin of Heredity
 DNA evolved from
RNA
 Scientists are still
unsure of how RNA
and DNA originally
formed
 How life formed is still
a theory, not a proof
Any Questions?