Transcript Oceanography Chapter 1

Oceanography
Chapter 1
Scientific Method
• Quiz Friday on science
• Link on scientific method
• http://teacher.nsrl.rochester.edu/phy_labs/Ap
pendixE/AppendixE.html
• Link on Nature of Science
• http://www.project2061.org/publications/sfaa
/online/chap1.htm?txtRef=&txtURIOld=/tools
/sfaaol/chap1.htm
Scientific Method
• Quiz Thursday
• Link on scientific method
•
Link to Big Bang Video
Nebular Hypothesis
• Earth and the rest of the
solar system formed
from a cloud of space
dust called a nebula.
• Most of the matter
condensed to form the
sun, small eddies
condensed to form
protoplanets
Animation
Nebular Hypothesis Link
http://atropos.as.arizona.edu/aiz/teachi
ng/nats102/mario/solar_system.html
Sun
• Eventually material
concentrated so much that a
process called fusion was
triggered.
• Fusion: Hydrogen atoms
combine to release
tremendous amounts of
energy
Formation of Earth
• Link to
formation of
Earth
http://atropos.as.arizona.edu/aiz/teaching/nats102
/mario/solar_system.html
• Link to video
• Link to video
• Link to video
Sources of Heat on Earth
1. from the remnants of heat from impacts
(meteors, asteroids, comets)
2. a remnant of an early Earth event known as
the Iron Catastrophe – migration of materials
cause friction.
3. from compression due to gravity.
4. from the decay of radioactive elements
Density Stratification
•As Earth condensed its internal heat became so
intense that it became molten.
•Denser elements migrated towards the core, lighter
towards the surface causing density stratificationmaking layers of the Earth’s internal structure
according the density. Density = Mass/Volume
•These layers can be characterized by either their
chemical or physical composition.
•Interior of Earth Lab.
Chemical Composition
• Chemically the Earth can be divided into 3
layers.
1.Crust – a thin 20 mi. layer composed of lowdensity rocks made of silica minerals-two
types: oceanic and continental crust
2.Mantle -1800 mi. thick made of high density
iron and magnesium silicate rock
3.Core- 1800 mi. made of higher density metal (
Ni and Fe)
Crust
Mantle
Most volume
cMc
Core
Physical Properties-5 layers
1. Lithosphere – cool, brittle outermost layer 62 mi.
Plates of the lithosphere move on the Earth.
2. Asthenosphere- 62-430 mi forming the upper
mantle. It is hot enough to melt portions of rock
making them plastic (flowing with gradual force) –
with high viscosity (resistant to flow).
3. Mesosphere- to 1800 mi., making the middle to
lower mantle. It is rigid.
4. Outer core- liquid and capable of flowing
5. Inner core- rigid and does not flow
LAMOI
Lithosphere
Asthenosphere
Mesosphere
Outer Core
Inner Core
Structure of Earth Link
http://atropos.as.arizona.edu/aiz/teaching/nats10
2/mario/solar_system.html
Lithosphere includes the
crust plus the upper
mantle and acts as a single
unit
Oceanic Crust under the
oceans is composed of
high density basalt is
about 5 mi thick
Continental Crust is
composed of low density,
lighter colored granite. Ave
22 mi thick.
What would happen if this guy
stepped off the boat?
Mr. Wizard Video
A glacier or mountain would be
analogous to the containers, the
lithosphere or crust would be
analogous to the ship,
the mantle or aesthenosphere
would be analogous to the water
First Atmosphere
Composition - Probably H2, He
• These gases are relatively rare on Earth compared to other
places in the universe and were probably lost to space early in
Earth's history because
– Earth's gravity is not strong enough to hold lighter gases
– Earth still did not have a differentiated core (solid
inner/liquid outer core) which creates Earth's magnetic
field (magnetosphere = Van Allen Belt) which deflects solar
winds.
• Once the core differentiated the heavier gases could be
retained
Second Atmosphere
• Produced by volcanic out gassing. Gases produced were
probably similar to those created by modern volcanoes (H2O,
CO2, SO2, CO, S2, Cl2, N2, H2) and NH3 (ammonia) and CH4
(methane)
• No free O2 at this time (not found in volcanic gases).
• Ocean Formation - As the Earth cooled, H2O produced by out
gassing could exist as liquid in the Early Archean, allowing
oceans to form.
– Evidence - pillow basalts, deep marine sediments in
greenstone belts.
– Link to Goldilocks principle activity
Oparin and Haldane
• Proposed that from the
simple inorganic molecules
on Earth’s early
atmosphere life could form.
• The first step would be to
form organic molecules to
build the first cell.
Figure
Miller-Urey
Experiment
Miller and Urey tests
out17-8
Oparin
and Haldane’s
hypothesis
Section 17-2
Mixture of gases
simulating
atmospheres of
early Earth
Spark simulating
lightning storms
Condensation
chamber
Water
vapor
Cold water
cools
chamber,
causing
droplets to
form
Liquid containing
amino acids and
other organic
compounds
Methane
Miller and Urey simulated Earth’s
early atmosphere
electricity simulated lightning
Why did they use uV light?
Ammonia
Hydrogen
Experiments have
produce all 20 amino
acids, sugars, lipids,
purines, pyrimidines
What is the importance of amino
acids?
What is the importance of nucleic
acids?
Polymerization led to proteins and nucleic acids such as RNA
Lightning and uV light provided energy for polymerization
Chemical Evolution
Abiogenesis
Proposed by Oparin and Haldane
The abiotic synthesis of monomers
Polymerization of monomers
Aggregation of molecules into protobionts
Origin of heredity
6. Natural section could refine protobionts containing
hereditary information
Once primitive RNA genes and their
polypeptide products were packaged
within a membrane, the protobionts
could have evolved as units.
Molecular cooperation could be refined
because favorable components
were concentrated
together, rather than
spread throughout the surroundings.
Fig. 26.13
Liposomes behave dynamically, growing by engulfing smaller
liposomes or “giving birth” to smaller liposomes.
Fig. 26.12a
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Protobiont Examples
Coacervate (Oparin) made of polypeptides
nucleic acids and polysaccharides
Proteinoid Micorspheres (Fox)
Liposomes (from previous slide)
All protobionts:
Selectively Permeable membrane
Have simple means of storing and releasing
energy
Split like they’re reproducing
Why Pre-cells with a membrane
have an evolutionary advantage
• Membranes help to separate the internal and
external environments
• There can be some control over what gets in and out
• They help to concentrate substances in an area
• Can form spontaneously when polypeptides and
phospholipids are heated together
Selective advantage for those that
could metabolize
• As cells or pre-cells multiplied there would
eventually be a shortage of material
• Those that could metabolize their own
molecules had an advantage.
RNA probably the first
genetic molecule
RNA could not only replicate
itself, but it could also act as a
catalyst
eg. Making proteins
RNA with the best autocatalytic
activity would predominate
Characteristic of First Cell
• All had DNA
• All use the same genetic code.
• Most similar organisms to first cell is
eubacteria.
• First cells were heterotrophic
First photosynthesis probably used hydrogen sulphide and hydrogen gas for electrons
instead of water 3.6 bya
Cyanobacteria= Blue Green Algae 3 bya
produced oxygen for respiration and ozone layer
How we got an Oxidizing
Atmosphere
• Today, the atmosphere is ~21% free oxygen. How did oxygen reach these levels in
the atmosphere? Revisit the oxygen cycle: Oxygen Production
– Photochemical dissociation - breakup of water molecules by ultraviolet light
• Produced O2 levels approx. 1-2% current levels
• At these levels O3 (Ozone) can form to shield Earth surface from UV
– Photosynthesis - CO2 + H2O + sunlight = organic compounds + O2 - produced
by cyanobacteria, and eventually higher plants - supplied the rest of O2 to
atmosphere. Thus plant populations produced O2.
• Oxygen Consumers (reduces oxygen)
– Chemical Weathering - through oxidation of surface materials
– Animal Respiration (much later)
– Burning of Fossil Fuels (much, much later)
Concept Map
Section 17-2
Evolution of Life
Early Earth was hot; atmosphere contained poisonous gases.
Earth cooled and oceans condensed.
Simple organic molecules may have formed in the oceans..
Small sequences of RNA may have formed and replicated.
First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.
Later prokaryotes were photosynthetic and produced oxygen.
An oxygenated atmosphere capped by the ozone layer protected Earth.
First eukaryotes may have been communities of prokaryotes.
Multicellular eukaryotes evolved.
Sexual reproduction increased genetic variability, hastening evolution.
How Old is the Earth?
• The generally accepted age for the Earth and the rest of the solar system is
about 4.55 billion years (plus or minus about 1%). This value is derived
from several different lines of evidence.
• Unfortunately, the age cannot be computed directly from material that is
solely from the Earth. There is evidence that energy from the Earth's
accumulation caused the surface to be molten. Further, the processes of
erosion and crustal recycling have apparently destroyed all of the earliest
surface.
• The oldest rocks which have been found so far (on the Earth) date to
about 3.8 to 3.9 billion years ago (by several radiometric dating methods).
Some of these rocks are sedimentary, and include minerals which are
themselves as old as 4.1 to 4.2 billion years. Rocks of this age are relatively
rare, however rocks that are at least 3.5 billion years in age have been
found on North America, Greenland, Australia, Africa, and Asia.
Radiometric dating measures the decay of
radioactive isotopes in terms of half-life
Half-life is the amount of time it takes for
½ the amount of a radioactive isotope to
decay
The half-life of Carbon 14 is 5,600 years
If you had 1 gram of carbon 14, how much
would be left after 6 half lives? 0.015 g
How many years would that take? 33,600 yrs
Why would be measuring a million year old
fossil using C14 not be possible?
How do you date a million year old fossil?
Meteor video