Transcript Formation of Earth

Origin of Life on Earth
Formation of Earth
Our knowledge of earth’s history
•Hypotheses about Earth’s early history are based on a
relatively small amount of evidence.
•Gaps and uncertainties make it likely that scientific ideas
about the origin of life will change.
Formation of our Planet
• Evidence shows that Earth was not “born” in a
single event.
• Pieces of cosmic debris were probably attracted
to one another over the course of 100 million
years.
• While Earth was young, it was struck by one or
more objects, producing enough heat to melt
the entire globe.
Formation of Earth
• Once Earth melted, its elements rearranged
themselves according to density.
• The most dense elements formed the planet’s core.
• Moderately dense elements floated to the surface,
cooled, and formed a solid crust.
• The least dense elements formed the first atmosphere.
Elements/ molecules/ compounds of early Earth
– Earth's early atmosphere probably contained
hydrogen cyanide, carbon dioxide, carbon monoxide,
nitrogen, hydrogen sulfide, and water.
– Notice the early atmosphere had NO oxygen.
– Had frequent storms with lightning
– High ultra-violet light (no ozone layer)
Big Events on Planet Earth
• Scientists infer that about four billion years ago, Earth
cooled and solid rocks formed on its surface.
• Millions of years later, volcanic activity shook Earth’s
crust.
• About 3.8 billion years ago, Earth’s surface cooled
enough for water to remain a liquid, and oceans
covered much of the surface.
IB LEARNING OBJECTIVE
• Describe four processes needed for the spontaneous
origin of life on Earth.
Requirements for Life as we know it.
• The following steps would have to occur for life as we know it to
evolve:
– The non-living synthesis of simple organic molecules
– The assembly of these molecules into polymers
– The development of self-replication molecules, such as
nucleic acids (DNA, RNA)
– The packaging of these molecules within membrane sacs,
so that an internal chemistry can develop, different from
the surrounding environment.
IB Learning Objectives
• Outline the experiments of Miller and Urey into the
origin of organic compounds.
The First Organic Molecules
• The First Organic Molecules
• Could organic molecules have evolved under
conditions on early Earth?
• In the 1950s, Stanley Miller and Harold Urey
tried to answer that question by simulating
conditions on the early Earth in a laboratory
setting.
The First Organic Molecules
• Miller and Urey’s Experiment
Mixture of gases
simulating
atmosphere of
early Earth
Water
vapor
Spark simulating
lightning storms
Condensation
chamber
Cold water cools
chamber, causing
droplets to form.
Liquid containing amino
acids and other organic
compounds
The First Organic Molecules
– Miller and Urey's experiments suggested how
mixtures of the organic compounds necessary for
life could have arisen from simpler compounds
present on a primitive Earth.
– Although their simulations of early Earth were not
accurate, experiments with current knowledge
yielded similar results.
Miller & Urey’s Experiment
• In order to discover how organic molecules evolved on
earth, they recreated the conditions of early Earth.
– In their apparatus they mixed the gases:
• Ammonia
• Methane
• Hydrogen
– To form a reducing atmosphere.
Miller Urey’s Experiment
• The ran electric charges and the boiling and
condensing of water simulated lightening and rainfall .
Miller & Urey’s Experiment
• What they discovered:
– They ran the experiment for one week.
– After one week the water turned murky brown.
– Inside the water they found 15 amino acids.
• What they concluded:
– Organic compounds ( the building blocks of life)
could have spontaneously formed in early earth
before there were any living organisms
Miller & Urey Experiment Animations
• http://bcs.whfreeman.com/thelifewire/content/chp03
/0301s.swf
• http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapter26/
animation_-_miller-urey_experiment.html
• http://bcs.whfreeman.com/thelifewire/content/chp03
/0302001.html
IB Learning Objectives
• Discuss possible locations where conditions would
have allowed the synthesis of organic compounds
About 3.5 billion years ago life evolved
Ideas of the origin of organic molecule
•Three ideas about where the first organism molecules
came from
– Miller & Urey’s Experiment suggest they could
have originated on Earth spontaneously.
– Hydrothermal Vents
– Extraterrestrial origin (comets, meteorites)
Submerged Volcanoes
• Instead of forming in the atmosphere, the first organic
compounds may have been synthesized near
submerged volcanoes and deep-sea vents
Video: Hydrothermal Vent
Video: Tubeworms
http://exploringorigins.org/fattyacids.html
Video on Organic Molecules forming in
Hydrothermal vents.
Extraterrestrial Sources of Organic Compounds
• Some organic compounds from which the first life on
Earth arose may have come from space
• Carbon compounds have been found in some
meteorites that landed on Earth
• This idea is called panspermia