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►The Universe, Solar System, and Earth
►The Origins of Life
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We Are Not Alone

Where did Earth, the solar system, and the stars come from?
Where did life come from?
When we ask these questions, we are really asking where did we
come from.
Origin of the Universe
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Our universe began as a concentrated single point, containing all known matter and energy.
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Chapter 3 Pages 3-1 to 3-5
The Universe, Solar System, and Earth
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Approximately 3.7 billion years ago this single point began to expand – an event known as the
Big Bang.
The universe has been expanding ever since.
Matter is not distributed uniformly throughout
the universe.
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A natural property of matter, gravity, began attracting helium
and hydrogen atoms together.
As the density increased, matter collapsed and compacted
under its own weight, causing a warm, dense core
called a protostar.
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Origin of the Universe (continued)
Chapter 3 Pages 3-4 & 3-5
The Universe, Solar System, and Earth
 The theorized “life cycle” of a star:
 The nuclear fusion reaction from protostars
creates stars.
 The star burns for millions of years,
consuming it’s hydrogen.
 Heavy elements form as hydrogen atoms fuse
during the “life-cycle” of a star.
 The core becomes denser and eventually
collapses under the extreme gravity forces
generated by the density.
 The star may explode causing a supernova.
 Supernova explosions account for the
distribution of heavy elements throughout the universe.
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Origin of the Solar System
 The sun, Earth, and other planets in the solar
system are only one of the millions of such
systems that make up the Milky Way Galaxy.
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Chapter 3 Pages 3-5 & 3-6
The Universe, Solar System, and Earth
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The current theory of how our solar system formed, with
the planets orbiting the sun, began with a large cloud
of hydrogen and helium called a nebula.
A shock wave from a supernova caused the
cloud to condense, which caused it to spin.
As the cloud collapsed and became denser,
it flattened in a disk due to the rotation. At the
center a protostar developed and began the
nuclear fusion process, becoming the sun.
 Some gas continued to revolve around the sun,
eventually condensing into masses too small to
become stars – they became the planets.
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This theory that the solar system originated as a
nebula is called the nebular theory.
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Origin of the Earth…
 Accretion is the process by which small particles clump
together because of gravity. As a mass grows the more
gravity it has, the more additional mass it attracts.
 The Earth’s growing mass caused its core to compress
causing the core to heat and become molten liquid.
The outer core is still molten.
 With this molten liquid, heavy matter, iron and nickel, sank toward
the center, while light matter, oxygen and silicon, moved toward
the surface. This process of density stratification formed the layers of the Earth.
Chapter 3 Pages 3-6 to 3-8
The Universe, Solar System, and Earth
 According to nebular theory, Earth (and other solar
system planets) formed through accretion.
…and Moon
 The most widely accepted theory for the moon’s origin is the Orpheus theory.
 Orpheus theory says that a planet-sized body struck Earth during its early
development and sent some of its material into orbit, forming the moon.
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Origin of the Atmosphere and Oceans
 The surface was still so hot that when water vapor formed clouds, then rain, the rain
boiled off again when it hit the ground.
 Finally, the Earth cooled enough to allow the rainwater to accumulate and the oceans
formed as water vapor condensed.
 The process that allowed life to form began with development of
the oceans.
 Carbon dioxide dissolved into young oceans, leaving a nitrogen-rich atmosphere.
Scientists think these were the conditions required for life.
 Ozone, an oxygen molecule found high in the atmosphere, is also important because it
protects life from ultraviolet radiation.
Chapter 3 Page 3-8
The Universe, Solar System, and Earth
 When the Earth cooled enough for the surface to form a crust, gases from
volcanic activity escaped accumulating as an early atmosphere.
 There was no oxygen in the early atmosphere as it was not needed.
 Oxygen, essential to life today, entered the atmosphere about 1.5 billion years
ago when photosynthesizing organisms began using carbon dioxide and
releasing oxygen.
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Abiogenesis
 There is fossil evidence that life began in the ocean. Scientists have found that
marine life fossils are significantly older than fossils of terrestrial life.
 Cyanobacteria, some of the oldest marine fossils, are dated 3.5 billion years old –
this suggests that life began in the sea.
 It is not clear how the first molecules that comprise the
building blocks of life originated.
Chapter 3 Pages 3-10 to 3-11
The Origins of Life
 The Urey-Miller experiment (1953) did not produce life, but did
prove that basic molecules used by living systems readily form
under certain conditions.
 Regardless of the exact environment that allowed life to happen, biologists
propose that simple molecules randomly combined and separated.
Eventually larger, more stable molecules formed by chance.
 When one of these combinations became capable of reproducing itself, life was born.
 This origination of life from nonliving matter is called abiogenesis, sometimes
referred to as spontaneous generation.
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Oxygen and Evolution
 Heterotrophs are organisms that rely on consuming compounds to obtain
chemical energy.
 Autotrophs can create organic chemical energy compounds from inorganic
compounds and an external energy source.
Chapter 3 Pages 3-12 & 3-13
The Origins of Life
 The appearance of autotrophs was significant because they break down carbon dioxide
into oxygen.
 Oxygen is important to life because oxygen reactions allow organisms to use
chemical energy more effectively.
 The theory of evolution, originally proposed by Charles Darwin, is based on
the principle that in nature, various characteristics affect survival. Those with
favorable characteristics are more likely than those with less favorable
characteristics to survive and reproduce.
 The theory of evolution says that over millions of years natural selection and mutation
caused the development of all the different life forms and their characteristics.
 In other words, organisms became more varied and complex over the millions
of years.
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Environment Classification Methods
 Marine scientists classify marine environments into many different regions
based on physical characteristics. They may classify parts of the ocean into
different zones or regions based on the light, depth, temperature, density,
latitude, and distance from shore or a combination of these.
 The most basic division of the ocean based on location is between the water
column and the bottom.
 The Pelagic zone is the water column portion. The pelagic zone is divided into
two horizontal zones:
Chapter 3 Pages 3-17 & 3-18
Ocean Zones and Life Styles
Location
 1. Neritic zone is the water area between the low tide mark to the edge of the
continental shelf.
 2. Oceanic zone is the open water area beyond the neritic zone.
The oceanic zone is further divided into five vertical regions: the epipelagic zone, the
mesopelagic zone, the bathypelagic zone, the abyssalpelagic zone, and the
hadalpelagic zone.
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Location (continued)
Chapter 3 Pages 3-18 & 3-19
Ocean Zones and Life Styles
 The five vertical regions of the oceanic zone:
 1. Epipelagic zone - top
layer sunlight penetrates.
 2. Mesopelagic zone sunlight reaches but not
strongly enough to support
much life.
 3. Bathypelagic zone deep water in open ocean.
 4. Abyssalpelagic zone - even
deeper water in oceanic trenches.
 5. Hadalpelagic zone - is the deepest
water in the ocean trenches.
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Location (continued)
 Supralittoral zone - This is the zone that water
splashes, but it does not remain submerged.
 Littoral zone - The bottom area between the
high- and low-tide mark so that it is sometimes
submerged and sometimes above water.
 Continental shelf - Area beyond the littoral
zone. This area is divided further.
Chapter 3 Pages 3-19 & 3-20
Ocean Zones and Life Styles
 The bottom is the Benthic zone.
This zone is divided based on depth-moving
from shore to open ocean.
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Sublittoral zone - ocean bottom close to shore.
Outer sublittoral zone - ocean bottom out to edge of continental shelf.
Bathyal* zone - is the bottom along the continental slope down to deep open ocean bottom.
Abyssal* zone - deep open ocean bottom.
Hadal* zone - deepest zone; below 6,000 meters (19,685 feet).
*Also called the deep sea floor.
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Marine Lifestyles
 Marine life is incredibly diverse. Scientists use
groups and subgroups based on common physical
characteristics to discuss them.
 Plankton are the group of organisms that exist
adrift in the ocean currents.
Chapter 3 Pages 3-20 to 3-22
Ocean Zones and Life Styles
 Neuston is an important subgroup of plankton.
Neuston are those plankton that float at the surface,
for example the Portuguese man-of-war.
 Nekton are the organisms that swim, from small
invertebrates to large whales. Most of the seas’
predators are nekton. The majority of nekton
are vertebrates.
 Benthos are organisms that live on or in the bottom.
They can move about or be sessile. Sessile organisms
are attached to the sea floor.
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Marine Lifestyles (continued)
 Epifauna are those animals, such as crabs,
that live on the sea floor.
 Epiflora are plants, such as seagrasses,
that live on the sea floor.
 Infauna are organisms that are
partially or completely buried in
the sea floor, such as clams, sand
dollars, tubeworms, and sea pens.
Chapter 3 Page 3-22
Ocean Zones and Life Styles
 Benthos are divided into:
 Most infauna are either
deposit feeders or suspension feeders.
 Deposit feeders feed off
detritus drifting down from above.
 Suspension feeders filter particles
(mostly plankton) suspended in
the water for food.
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