EARTH AND LIFE SCIENCE NOTES Prof. Ben T.

Mendiola
• Atom—smallest unit of an element composed of electrons, neutrons and protons.
• Molecules—union of two or more atoms of the same or different elements.
• Cell—the structural and functional unit of all living things.
• Tissue- a group of cells with a common structure and function.
• Organ—composed of tissues functioning together for a specific task.
• Organ system—composed of several organs working together.
• Organism—an individual; complex individuals contain organ systems.
• Population—organisms of the same species in a particular area.
• Population—group of individuals of the same species living in a given area or habitat at a given time.
• Community—interacting populations in a given area.
• Community—includes all the populations inhabiting a specific area at the same time.
• Ecosystem—a community plus the physical environment.
• Ecosystem—a biotic community and its abiotic environment functioning as a system (first used by A. G. Tansley.)
• Biosphere—regions of the Earth’s crust, Waters and atmosphere inhabited by living things; Zone of air, land and water
where living organisms are found.

Astronomy is a natural science that deals with the study of celestial objects (such as moons, planets, stars, nebulae, and
galaxies); the physics, chemistry, and evolution of such objects; and phenomena that originate outside the atmosphere of Earth
(such as supernovae explosions, gamma ray bursts, and cosmic background radiation).

• It is the study of all matter and Energy in the universe involving celestial bodies such as planets, stars, and galaxies.
• The Universe as a whole is an abstract concept but it consists of real physical places where everything else exist.
• The planets, satellites and meteoric materials, and the sun did not exist 4.6 billion years ago.
• Samples from the earth, the meteorites and the moon suggests that the solar system formed from preexisting matter
within an interval of about 30 to 100 billion years ago.
Prior to that time, the atoms were floating in clouds of thin gas in interstellar space. It is remarkable that this matter somehow
aggregated not only into a dazzling star–the sun–but also into family of surrounding planets.

• Phenomena/phenomenon-observable occurrence---something experienced: a fact or occurrence that can be observed

or something notable: something that is out of the ordinary and excites people's interest and curiosity.
• A related but distinct subject, cosmology, is concerned with studying the universe as a whole.
• Cosmology -study of the origins and eventual fate of the universe
• Universe–all matter and energy in space: the totality of all matter and energy that exists in the vastness of space,
whether known to human beings or not.
• Astronomy is one of the oldest sciences.

ORIGIN OF THE SOLAR SYSTEM

Nebular Hypothesis– Immanuel Kant in 1755 and Laplace in 1796 postulated that that the solar system was derived
from the condensation of an enormously dispersed gaseous sphere surrounding the sun.
Increased rotational velocity of this atmosphere during condensation was assumed to have produced a discoidal
shape, the plane of the disk coinciding with that of the sun’s equator.(Discoid-flat round object: a disk-shaped
object or part)
When the velocity reached a critical point , centrifugal force would throw off part of the gas as a ring and material
of each ring gradually assembled into a gaseous globe, which eventually became a solid planet revolving around the
sun in a circular orbit like that of the ring from which it was formed.(Centrifugal force -force pulling away from
center: an apparent force that seems to pull a rotating or spinning object away from a center. Centripetal- force
pulling toward center: a force that pulls a rotating or spinning object toward a center or axis).
While these gaseous globes were contracting, most of them abandoned the rings, which assembled into satellites
revolving in circles around these planets.

According to this hypothesis, the solar system developed with observed regularities in its motions.

i. Beginning as a rotating cloud

ii. Most of the mass became concentrated at the center to form the sun; the remaining material condensed and
accumulated to form the planets
iii. The present solar system where our planet, the earth, is the third planet from the sun.
 Planetisimal Hypothesis
It supposed that the planetary system was formed from materials removed from the sun by great
gravitational attraction. The gaseous projection was pulled from the sun by tidal action caused by a passing
star.
The projection became masses of gases which revolved around the sun. At first, the masses were very hot.
They cooled and contracted and became solid bodies of varying sizes and distances from the sun.
The larger bodies attracted smaller ones and became planets. The smaller bodies became asteroids,
meteors and satellites of planets.

Dust Cloud Theory

German Physicist Carl Friedrich von Weizsacken & U.S. Chemist Harold Urey in 1945- the nebula was
assumed to have a composition mainly of helium and hydrogen, like the sun, with only 1% of heavier
elements.
The mass of this Dust Cloud was originally 10% of the sun’s mass and about a hundred times as great as
the present combined mass of the planets and satellites.
The nebula was much flattened by its rotation, which was of the planetary type in that the gas molecules
moved faster as they were closer to the sun.
Interactions of the gas molecules accelerated the lighter ones so that they mostly escaped from the
nebula.
The interactions also produced swirls, forming lumps in the nebula that could grow to become planets and
satellites.
Nebula-space dust: a region or cloud of interstellar dust and gas appearing variously as a hazy bright or
dark patch.

Protoplanet Theory

Proposed by Gerald P. Kuiper

The Original nebula was so massive that on further contraction and flattening, it broke into separate
clouds or protoplanets
These remained stable in the tidal field of the sun.
As they contracted, they developed denser cores surrounded by large atmospheres of the lighter gases.
Later, the shrinking primitive sun became hot enough to emit powerful corpuscular and ultraviolet
radiations.
The radiations drove away into space remnants of the nebula and the large atmosphere of the planets,
which look like a swarm of comets with tails.
This hypothesis proposed a process that could have developed planetary systems around many stars.
Indeed, it has been surmised that the majority of the yellow stars, like the sun, may possess systems of the
planets.

SOLAR SYSTEM

In our solar system, there are at least eight planets orbiting the Sun.

Because of the way in which the solar system formed, each planet developed particular characteristics based on its
distance from the Sun.

In general, small rocky planets are located close to the Sun and large gaseous planets are further away.

Because of the difference in temperature

in the inner and outer parts of the disk, two
different types of planets were formed.
 Closer to the center of the disk where the Sun was forming, rocks and metals condensed to create the
terrestrial planets.

The eight major planets orbiting the Sun can be grouped into two categories.

The four inner planets—Mercury, Venus, Earth, and Mars—are terrestrial planets.
They are relatively small, with rocky surfaces and metal cores.
The four outer planets—Jupiter, Saturn, Uranus, and Neptune—are called Jovian planets.
They are relatively large and cold, and have a gaseous composition.

Farther away from the Sun, where it was cold enough for the abundant levels of hydrogen to form ice, the outer
planets grew much larger than those made of metals and rocks.

In addition, the larger mass and gravity of the growing Jovian planets allowed them to capture the abundant
hydrogen and helium gases, turning them into gaseous giants.

The scale of the solar system is so large that it is very difficult to accurately represent both the size of the planets and
the distance between them.

However, on an accurate scale model, if the Sun were about the size of an 8-inch ball, Earth would be about the size
of a peppercorn located about 26 yards away from the ball and Pluto would be smaller than a pinhead located about
half a mile away.

i. Pluto, sometimes called the ninth planet, is an oddball—a tiny, solid, icy world with a very elliptical and
distant orbit.
ii. These characteristics have led scientists to believe that Pluto is actually a member of the Kuiper belt—a
collection of comets that orbit the Sun beyond Neptune.
iii. In July 2005, a new large Kuiper belt object was discovered.
iv. It is larger than Pluto and has an orbit about three times as distant.
v. If Pluto is considered a planet, then this new object is a tenth planet.
This image shows the approximate sizes of the planets relative to each other, and displays them in the order of their
distance from the Sun

Origin of Life on Earth

Science shows us that the universe evolved by

self-organization of matter towards more and
more complex structures.
Atoms, stars and galaxies self-assembled out of
the fundamental particles produced by the Big
Bang.
In first-generation stars, heavier elements like
carbon, nitrogen and oxygen were formed.
Aging first-generation stars then expelled them
out into space – we, who consist of these
elements, are thus literally born from stardust.
The heaviest elements were born in the
explosions of supernovae. The forces of gravity
subsequently allowed for the formation of
newer stars and of planets.
Finally, in the process of biological evolution from bacteria-like tiny cells (the last universal common ancestor,
abbr. LUCA) to all life on earth, including us humans, complex life forms arose from simpler ones.
 First Hominids Hominids
Mammals
Dinosaurs
Land plants
Animals
First vertebrate land animals Multicellular life
Eukaryotes
Formation of the moon Prokaryotes
Late Heavy Bombardment

HADEAN

Photosynthesis starts

CENOZOIC

MESOZOIC

PALEOZOIC

ARCHEAN

PROTEROZOIC

Atmosphere becomes oxygen rich

The experimental study of the origin of life kick-started with

Miller’s ‘prebiotic soup’ experiment which produced amino acids,
essential to life.
The famous ‘prebiotic soup’ experiment by Stanley Miller
had shown that amino acids, the building blocks of proteins, arose
among other small organic molecules spontaneously by reacting a
mixture of methane, hydrogen, ammonia and water in a spark
discharge apparatus.
RNA acted as a precursor of both protein and DNA

The Formation of Chemical Building Blocks

As the Earth cooled, much of the atmospheric water would
have condensed and fallen as rain, creating large oceans.
Dissolved in the rain was carbon dioxide, which form
carbonate rocks such as limestone and marble.
Through this process, most of the carbon dioxide was
removed from the atmosphere, allowing the Earth to escape from a
possible runaway greenhouse effect
The next step in the development of life was the formation of simple organic molecules.
 In a famous experiment conducted in 1952, Stanley Miller and Harold Urey exposed a mixture of gaseous
hydrogen, ammonia, methane and water to an electrical arc for a week.

At the end of the experiment, the reaction chamber was coated with a reddish-brown rich in amino acids and
other compounds essential to life.

MILLER- UREY EXPERIMENT

The Miller-Urey experiment demonstrated

how lightning may have converted the evolutionary
atmosphere into a living atmosphere, rich in the
chemical building blocks of life.

However, it is important to understand that

the experiment did not create life!
A number of further steps, which have not
yet been demonstrated experimentally, are
required before life is formed.

The Formation of Macromolecules

After the formation of the amino acids and other building blocks, and their subsequent solution in liquid
water, various processes (such as adsorption on clay particles, or confinement in evaporating pools) would
have conspired to concentrate these compounds.
Under the influence of an energy source (such as UV light or heat), the concentrated compounds would
have combined to form large macromolecules, such as polypeptides (precursors of proteins) and
polynucleotides (precursors of DNA).

The Formation of Prebionts

Once macromolecules had formed, the next step in the development of life would have involved their
organization into bodies with definite shapes and chemical properties.
One example is coacervate droplets, which may be the early ancestors of cells.
These coacervates consist of macromolecules surrounded by a shell of water molecules, whose rigid
orientation makes them form a primitive membrane.
This membrane is highly selective, allowing only certain molecules to pass though; it therefore creates
a sheltered chamber in which complex chemical reactions can develop
The Formation of Prokaryotic Organisms

With ever-more complex reactions taking place in prebionts, a point was reached where self-replicating
molecules were formed.
One example is the nucleic acids, such as DNA and RNA.
These molecules have the ability to copy themselves, and therefore act as information stores.
Due to random mutations occurring during the copying process, the appearance of self-replicating molecules
meant that the prebionts began to evolve through the process of natural selection.
Only those prebionts which were able to make the best use of the available sources of energy and raw
materials were able to survive and produce a new generation of prebionts, containing the genetic
information of their own "parents".
At the point, the prebionts had reached a level of advancement which amounted to living organisms (albeit
primitive).
These single-celled organisms were prokaryotic, meaning that they lacked an inner membrane around a
nucleus of genetic material. They were much like present-day bacteria.

The Evolution of Autotrophs

The first cells were heterotrophs, meaning that

they obtained their energy and raw materials (i.e.,
food) from their surroundings.
Early on in their existence, the supply of these
resources would have run short, amounting to a
famine.
This famine exerted extreme evolutionary pressure
on the heterotrophs, leading quite quickly to the
development of cells which were able to produce
their own food via photosynthesis.
These new autotrophs (meaning that they create
their own food, rather than relying on their surroundings) would have at first relied on a variant of
photosynthesis based around hydrogen sulphide.
Unfortunately, the supply of hydrogen sulphide is rather limited on Earth, being found only around areas of
volcanic activity.
Therefore, some autotrophs (the cyanobacteria) subsequently made the leap to using water instead, which is
of course in great abundance

The Evolution of Aerobic Organisms

When photosynthesis is based around water, it produces a significant by-product: oxygen.

Since oxygen was highly toxic to the cyanobacteria producing it, they were forced to evolve means of
protecting themselves from it, primarily by excreting it as a gas.
Their success in this led to the steady pumping of oxygen into the Earth's atmosphere.
Initially, the oxygen would have reacted with surface minerals to create oxides. This would have gone on until
about 2 billion years ago, when all of the available minerals were already oxidized.
At this juncture, the levels of atmospheric oxygen would have begun to rise, and a new type of heterotrophic
life evolved to take advantage of the oxygen as an energy source: the aerobic respirator

The Evolution of Eukaryotic Cells

Around 1.5 billion years ago, eukaryotic organisms

first appeared. Unlike prokaryotic organisms, these
possessed inner membranes around a nucleus of DNA,
and also contained sophisticated organelles such as
mitochondria (for aerobic respiration) and
chloroplasts (for photosynthesis).
 Subsequently, the eukaryotic cells developed into specialized colonies, and provided the basis for all
multi-cellular life known today.

The Present-Day Atmosphere

Until about 400 million years ago, the levels of oxygen in the atmosphere were steadily growing. However, at
this point the amount of oxygen produced by the photosynthetic autotrophs was balanced by the amount
consumed by the aerobic heterotrophs, and the growth stopped. Since then, the composition of the Earth's
atmosphere has remained relatively unchanged.
This present-day atmosphere has a composition of about 20% oxygen, 78% nitrogen, and small amounts of
water vapor and carbon dioxide.

Earth
Our planet is constantly changing.

Natural cycles balance and regulate Earth and its atmosphere. Human activities can cause changes to these
natural cycles.
Life on Earth is well adapted to our planet’s cycles.
In our solar system, Earth is the only planet with air to breathe, liquid water to drink, and temperatures that
are just right for life as we know it.
Because our existence depends on our planet and its climate, we need to understand how what we do affects
the Earth.
Scientists try to figure out how our planet works by studying Earth’s cycles.
Changes to Earth’s cycles can cause changes in the climates of our planet.
The more we know about these cycles, the more we will understand how humans are affecting them and how
that might change the planet. Click on the cycles below to learn more about how they work!
Earth is a complex, evolving body characterized by ceaseless change.
To understand Earth on a global scale means using a scientific approach to consider how
Earth's component parts and their interactions have evolved, how they function, and how they may be
expected to further evolve over time.
This visualization adapted from NASA helps explain why understanding Earth as an integrated system of
components and processes is essential to science education.
Ever since the first photos were sent back from space, our view of Earth has changed.
Remote sensing instruments, such as satellites, allow us to better understand the interrelationships between
the different subsystems.
For instance, recordings made by remote and Earth-based instruments show that significant surface warming
has occurred over the past three decades.
Knowing this, scientists are working to determine how this will affect — and already is affecting — the entire
Earth system
Understanding our planet as an integrated system of components and processes is a fundamental part of
Earth and space science research.
Just as the human body is composed of interrelated systems that control specific bodily functions, Earth's four
principal components — the atmosphere (air), lithosphere (land), hydrosphere (water), and biosphere (life)
— perform critical roles that, together, support and sustain life on the planet.
Nothing influences the subsystems that contribute to Earth's dynamic behavior more than heat.
Heat comes from two sources: solar energy and radioactivity in the Earth's core.
Because of the angle at which the Sun strikes Earth, Earth's surface is heated unevenly.
This creates Earth's three major climate zones — tropical, temperate, and polar — which then influence what
types of life flourish in different locations.
The uneven heating also controls weather systems.
The heat absorbed by the oceans and carried by its currents is constantly being released into the atmosphere.
This heat and moisture drive atmospheric circulation and set weather patterns in motion.
The weather patterns then influence vegetation, as well as erosion and sediment transport.
The other heat source, deep within Earth's core, is responsible for plate tectonics, which gives the Earth its
physical character: mountain ranges and valleys, ocean basins and lake beds, and islands and trenches.
The heat from Earth's core generates convection cells within its mantle, which help drive plate activity.
Layers of the Earth

LAYERS
OF THE
EARTH

ACCORDING TO COMPOSITION:

The Crust—Outermost layer

- Continental crust—crust under the continents or very large islands which is about 35 km thick. Rich in
Potassium, Sodium, aluminum and silicon. (Granitic---granite)
- Oceanic crust—crust beneath the oceans and much thinner (7 to 10 km). And it covers about 70.8% of the
earth’s surface. Rich in silicon, iron and magnesium (Basaltic---basalt)
Mantle – located below the crust and represents more than 80% of the volume of the earth. The boundary
between the crust and the mantle is called the MOHOROVICIC DISCONTINUITY.
Core – The metallic ball located at the center of the earth. Temperature range from 4000 to 5000 oC. The
boundary between the core and the mantle is called the GUTENBERG DISCONTINUITY. (G or the core-mantle
boundary or CMD)

LAYERS OF THE EARTH ACCORDING TO PHYSICAL PROPERTIES:

Lithosphere—rocky sphere composed of the continental crust and the uppermost mantle. Cool rigid layer.
Asthenosphere—(Upper mantle) rocks are very near melting points. The hotter asthenosphere is capable of
flowing. It exhibits a plastic behavior. When earthquakes occur, they send seismic waves (vibrations) through
the earth. Seismologists (scientists who study earthquakes and the internal structures of the earth) have
observed that seismic waves slow down when they pass a certain region within the asthenosphere, has been
called LVZ (low -velocity zone). Seismic waves slow down because of the presence of molten rocks.
Mesosphere (lowermost mantle)—It is solid despite the very high temperature s at this depth. This is because
pressures are also very high; the rocks are so highly compressed that the component atoms are prevented
from separating. Thus the rocks cannot melt.
Outer Core—is the molten portion of the core and exhibits the characteristics of a mobile liquid.
Inner Core—a metallic sphere and is the solid portion of the core.
MOVEMENTS OF THE EARTH

The Theory Of Continental Drift

By German Geologist Alfred Wegener in 1912, suggests that the continents today probably started as only one larger
continent which he called Pangaea (All the world), hypothesized that Pangaea broke apart into smaller pieces and
gradually moved away from one another.

Africa and South America has almost the perfect fit of the outlines of the continents.

PANGAEA- Land mass

EARTH – CONTINENTAL DRIFT THEORY

SCIENTIFIC EVIDENCES SUPPORTING CONTINENTAL DRIFT THEORY

1. The fit of the continents. The coastlines of Africa and South America on either side of the Atlantic Ocean seem to
fit each other. He suggested that the two continents were once joined together.

2. The similarity of fossils in different continents. Fossils are traces and remains of organisms that lived in
prehistoric times. More than 10,000 years ago, fossils of the reptiles Mesosaurus were found along the facing
coastlines of Africa and South America. The fossils were only limited on those areas, if they swum then they should
have been found in different places. Plant fossils were also found. The remains of fernlike Glossopteris were found
widely distributed in all continents. This was another evidence that the continents were all connected together in the
past. Glossopteris thrived only in subpolar climate.

3. The similarity of rock type and age along the matching coastlines. There is a close match between the rocks
found in the northwestern coast of Africa and the rocks found in Eastern Brazil, South America.

4. The continuity of the geologic features from continent to continent. Geologic features as mountain ranges, line
up along the matching coastlines. The Appalachian Mountains trend North east along the east coast of the United
States. On the other side of the Atlantic Ocean, in Scandinavia (northern Europe), another mountain belt of similar
age and structure is found. The mountains extend in nearly the same direction from one continent to the other. 5.

5. The presence of coal seams in ANTARTICA. Coal is formed from organic matter such as dead plants and animals.
Its presence in the Antarctica, which indicates that Antarctica was once closer to the equator because that is the
place where plants and animals, are abundant.

6. TILLITES. These are deposits of rock debris left by glaciers ( masses of ice that are formed by the accumulation of
snow). It is found in Africa, South America, Australia and India which is in a tropical place. Wegener believed that
these landmasses were once located in the South Pole, where it was colder.

Seafloor Spreading
—introduced by Harry Hess

Scientists discovered the following at the bottom of the sea:

i. The presence of a belt of underwater mountains (oceanic ridges) that encircles the globe.
ii. The presence of a central valley (rift Valley) at the summit of the oceanic ridges.
iii. The oceanic ridges, which are made up of volcanic rocks, are giving off an abnormal high amount of
heat.
iv. Earthquakes in the deep- sea areas were found to be associated with trenches.
v. The oldest seafloor is surprisingly young (only 170 million years old) compared to the oldest rocks on
land (more than 3 billion years old).
 RIDGE TRENCH
FRACTURE ZONE CREST
(INACTIVE)

LITHOSPHERE

ASTHENOSPHERE
TRANSFORM
FAULT

MID-OCEANIC
RIDGE

RIFT

CONTINENTAL
OCEANIC CRUST
CRUST

According to Hess, rock materials in the mantle are in motion. Hot mantle material slowly rises and then spreads
sideways. The seafloor above the spreading mantle material is then pulled apart. When the seafloor is torn apart,
molten rock from within the earth comes out through the break. The outpouring of molten rock forms new oceanic
crust and builds up the oceanic ridge. This is why the ridges are made up of volcanic rocks, and why they are giving
off heat. As the seafloor keeps on spreading, rocks sink or subside into the widening gap, forming a central valley.

Meanwhile, the spreading mantle material will carry the seafloor away from the ridge. Eventually, the mantle
material will lose heat. As it cools, the material becomes denser and starts to sink. This happens at the trenches,
where the seafloor descends into the earth, dragged down by the sinking mantle material.

New oceanic crust is formed at the ridges. It is slowly carried away toward the trenches, where it goes back inside
the earth. The sea floor therefore is being recycled. That is why it is so young.

According to Hess, hot materials in the mantle rise due to low density while relatively cooler materials sink because
of higher density. This makes the mantle materials circulate slowly, forming convection currents or convection cells,
which drive the seafloor into motion.

When the seafloor spreads apart, molten rock comes out and solidifies to form new seafloor. The new seafloor also
contains magnetite, which then keeps a record of the direction of the magnetic field at that particular time. When
the spreading of the seafloor was finally confirmed, another theory was developed that included both the continental
drift and seafloor spreading. This was called plate tectonics.
 Theory of Plate Tectonics

The Theory of Plate Tectonics suggests that the earth’s crust is divided into larger plates moving very slowly in
particular directions with respect to one another.

To understand earthquakes, we need to know something about the theory of plate tectonics. According to this
theory, the earth's 120-mile (200-km)-thick shell, called the lithosphere, is broken into several rigid slabs called
plates that slide over the uppermost layer of the mantle (Fig. 1). Seven major oceanic and continental plates have
been identified, along with a number of smaller plates. Moving at rates of 10 to 130 millimeters (0.4 to 5 inches) per
year, these plates interact with one another in various ways, producing mountain belts, volcanoes, and earthquakes
The movement of plates is described by the three types of plate boundaries:

A. DIVERGENT BOUNDARY

The plates are moving away from each other is called divergent boundary. This is where the lithosphere is being pulled apart.
Example is in Africa, The land was slowly torn apart as the plates moved in opposite directions. As the land started to break
apart, huge cracks or valleys were formed. These were later filled up with water from rain and nearby streams. The results are
narrow and elongated lake, such as Lake Malawi and Lake Tanganyika. Red Sea was also formed when Saudi Arabia Broke away
from Africa and the South Atlantic Ocean was also formed this way, when South America and Africa separated.

B. CONVERGENT BOUNDARY

Plates are moving toward each other and plates are colliding with one another.

Continental Plates are lithospheric plates that underlie the continents and those that lie beneath the oceans are Oceanic Plates.
Oceanic Plates are denser than continental plates.

Three scenarios may happen along convergent boundaries:

a. TWO CONTINENTAL PLATES MAY COLLIDE. When two continental plates collide, the rocks that are caught in between are
squeezed, crumpled and lifted up. In this process, mountains are built. Continental-continental plate collisions are mountain-
building processes.

b. TWO OCEANIC PLATES MAY COLLIDE. When two oceanic plates collide, one of the plates, whichever is denser, dives under
the other. This diving Process is called Subduction. Subduction leads to the melting of rocks in the mantle. The magma will
then rise to the earth’s surface to form a chain of volcanic islands called ISLAND arc. Example: Aleutian island in the North
Pacific Ocean and Tonga Islands in the South Pacific Ocean.

Subduction also leads to the formation of a Trench. A Trench is depression in the ocean Floor that marks the place where
one plate is diving under another plate. Trenches are at least 7 km. deep. Example: Java trench and Philippine Trench.
c. A CONTINENTAL PLATE AND AN OCEANIC PLATE MAY COLLIDE. When continental plate and an oceanic plate collide, the
oceanic plate (being the denser plate) subducts or dives under the continental plate. The process of subduction will produce a
trench and it will also initiate volcanism. Example: In South America, the Peru-Chile Trench feeds the volcanoes in the Andes
Mountains.

C. TRANSFORM BOUNDARY. Where two neighboring plates are neither spreading apart nor colliding with each other.
Instead, the plates are sliding past each other. Example: San Andreas Fault in California, U.S.

Simplified map of the earth's crustal plates (U.S. Geological

Survey, 1990, Professional Paper 1515).

Diastrophism- process which involves the movement of the earth’s crust such that a portion is pushed up,
pushed down or forced sideways

Deformation of rock involves changes in the shape and/or volume of these substances. Changes in shape and
volume occur when stress and strain causes rock to buckle and fracture or crumple into folds.

A fold can be defined as a bend in rock that is the response to compressional forces.

FOLDING- Process of bending of rocks deep in the crust. Folds are most visible in rocks that contain layering.

For plastic deformation of rock to occur a number of conditions must be met, including:

The rock material must have the ability to deform under pressure and heat.
The higher the temperature of the rock the more plastic it becomes.
Pressure must not exceed the internal strength of the rock. If it does, fracturing occurs.
Deformation must be applied slowly.

A number of different folds have been recognized and classified by geologists.

The simplest type of fold is called a

monocline. This fold involves a slight
bend in otherwise parallel layers of
rock.

An anticline is a convex up fold in rock

that resembles an arch like structure
with the rock beds (or limbs) dipping
way from the center of the structure.
 Syncline is a fold where the rock
layers are warped downward.

Both anticlines and synclines are the result of

compressional stress.

Anticlines may form mountain ridges and synclines would

be valleys.

Sometimes when the rocks fold they do not only fold but they crack or break due to pressure. The rock layers may slide or move
over one another along the break or fracture. This is faulting, which may occur vertically or horizontally. In vertical faulting
the rock layers may move upward’ thus destroying the continuity of the layers. Faulting is believed to be the most common
cause of earthquakes. Earthquakes resulting from diastrophic movements are said to be of Tectonic origin. Earthquakes that
originate beneath the sea produce big waves called tsunamis.

The Breaks in the rocks are called FRACTURES. The two types of fractures are FAULTS AND JOINTS.

Faults are breaks along which there is considerable movement. Joints are those breaks where there is little or no
movement.

Faults form in rocks when the stresses overcome the internal strength of the rock resulting in a fracture.

A fault can be defined as the displacement of once connected blocks of rock along a fault plane. This can occur in
any direction with the blocks moving away from each other. Faults occur from both tensional and compressional
forces.

Two types of faults:

1. Dip-slip faults. Involves movement of the

blocks of rock mainly in the vertical direction.
That is, the blocks of rock may move up and
down.

2. Strike slip faults. Involves movement chiefly

in the horizontal direction (sideways or laterally)

The figure shows the location of some of the

major faults located on the Earth.

The alternate hypothesis about how life arose on Earth is that of Spontaneous Generation. Not the
spontaneous generation of the17th century that Reddi, Leeuwenhoek, Spallanzalli, Tyndall, and Pasteur put
to rest, but the 1936 spontaneous generation of Oparin, a Russian biochemist, that non-cellular
macromolecular precursors developed into cells.
An abundance of energy sources was available on early Earth in the form of solar radiation (visible light,
ultra-violet light, x-rays), lightning, heat, cosmic rays, radioactive decay, or volcanic explosions.
Oparin's argument goes something like this:

1. The Universe formed approximately 20 billion years ago, followed by our solar system (the Sun and
planets) about 4-5 billion years ago.

Our solar system formed from a cloud of dust and gas which condensed into a single compact mass resulting
in tremendous heat and pressure.
Because of the heat and pressure, thermonuclear reactions were initiated creating the Sun. Lesser centers of
condensation occurred to the Earth and other planets.
Earth's condensation (and other terrestrial plants too) resulted in stratification of the components giving rise
to Fe + Ni at the Earth's center (the heavy metals) and H2 + He + other gases (the lighter elements) as the
primordial atmosphere.
But, because of the size of the Earth and its weak gravitational field, these gases escaped nearly immediately.
As a result the Earth became a bare, rocky globe with no oceans or atmosphere.
Time passes and gravity compresses the earth more. Radioactive decay occurs to produce heat and create a
molten interior. More stratification occurs to produce a core of molten Fe + Ni and a mantle of Fe and
magnesium silicates.
The heat of the core forces gases and water out by volcanic action. These gases formed a second atmosphere,
the evolutionary atmosphere.

2. The next step in the evolution of life would have been the formation of small organic molecules. The
combination of minerals, NH4+, CH4, H2, and H2O that formed the oceans is a very stable mixture so
how could the building blocks of life arise?

Some sort of energy source was necessary.

An abundance of energy sources was available on early Earth in the form of solar radiation (visible light,
ultra-violet light, x-rays), lightning, heat, cosmic rays, radioactive decay, or volcanic explosions.

The Primordial Earth

After its formation from planetesimals, the Earth would have

undergone chemical differentiation, where the heavier
elements sink to the core and the lighter elements rise to the
surface.
Among these lighter elements were traces of hydrogen and helium,
which would have given rise to a thin primordial atmosphere

Bombardment of primordial Earth

Since Earth's gravity is too low for it to retain hydrogen and helium, these gasses would quickly have
evaporated into space, leaving a bare rocky globe with no atmosphere or oceans.
However, the contraction of the Earth under its own gravity, plus the decay of radioactive elements and
bombardment by meteorites, would have then led to significant volcanic activity.
This activity forced out gasses from the interior to form a dense evolutionary atmosphere, comprised mainly
of water vapor, carbon dioxide and nitrogen.

The Formation of Chemical Building Blocks

As the Earth cooled, much of the atmospheric water would have condensed and fallen as rain, creating large
oceans.
Dissolved in the rain was carbon dioxide, which form carbonate rocks such as limestone and marble.
Through this process, most of the carbon dioxide was removed from the atmosphere, allowing the Earth to
escape from a possible runaway greenhouse effect.
The next step in the development of life was the formation of simple organic molecules.
In a famous experiment conducted in 1952, Stanley Miller and Harold Urey exposed a mixture of gaseous
hydrogen, ammonia, methane and water to an electrical arc for a week.
At the end of the experiment, the reaction chamber was coated with a reddish-brown rich in amino acids and
other compounds essential to life.
 From Soup to Cells—the Origin of Life

A microbe-like cellular filament found in 3.465 billion year old rock Evolution encompasses a wide range of
phenomena: from the emergence of major lineages, to mass extinctions, to the evolution of antibiotic
resistant bacteria in hospitals today.
However, within the field of evolutionary biology, the origin of life is of special interest because it addresses
the fundamental question of where we (and all living things) came from.
Many lines of evidence help illuminate the origin of life: ancient fossils, radiometric dating, the phylogenetics
and chemistry of modern organisms, and even experiments.
However, since new evidence is constantly being discovered, hypotheses about how life originated may
change or be modified.
It's important to keep in mind that changes to these hypotheses are a normal part of the process of science
and that they do not represent a change in the basis of evolutionary theory.

When did life originate?

Evidence suggests that life first evolved around 3.5 billion years ago.
This evidence takes the form of microfossils (fossils too small to be seen without the aid of a microscope) and
ancient rock structures in South Africa and Australia called stromatolites.
Stromatolites are produced by microbes (mainly photosynthesizing cyanobacteria) that form thin microbial
films which trap mud; over time, layers of these mud/microbe mats can build up into a layered rock
structure — the stromatolite.
Stromatolites are still produced by microbes today. These modern stromatolites are remarkably similar to the
ancient stromatolites which provide evidence of some of the earliest life on Earth.
Modern and ancient stromatolites have similar shapes and, when seen in cross section, both show the same
fine layering produced by thin bacterial sheets.
Microfossils of ancient cyanobacteria can sometimes be identified within these layers

FOSSILS Modern stromatolites in Shark Bay, Australia

Cross sections of 1.8 billion year

old fossil stromatolites at Great
Slave Lake, Canada

Where did life originate?

A hydrothermal vent at the bottom of the ocean Scientists are exploring several possible locations for the origin of
life, including tide pools and hot springs. However, recently some scientists have narrowed in on the hypothesis that
life originated near a deep sea hydrothermal vent.

The chemicals found in these vents and the energy they provide could have fueled many of the chemical
reactions necessary for the evolution of life.
Furthermore, using the DNA sequences of modern organisms, biologists have tentatively traced the most
recent common ancestor of all life to an aquatic microorganism that lived in extremely high temperatures — a
likely candidate for a hydrothermal vent inhabitant!
Although several lines of evidence are consistent with the hypothesis that life began near deep sea vents, it is
far from certain: the investigation continues and may eventually point towards a different site for the origin of
life.

Solar Radiation

Gaia Hypothesis

The hypothesis was formulated by the scientist James Lovelock and co-developed by the microbiologist Lynn
Margulis in the 1970s.

– The study of planetary habitability is partly based upon extrapolation from knowledge of the
Earth's conditions, as the Earth is the only planet currently known to harbor life.

The Gaia hypothesis, also known as Gaia theory or Gaia principle, proposes that organisms interact with
their inorganic surroundings on Earth to form a self-regulating, complex system that contributes to
maintaining the conditions for life on the planet.
Topics of interest include how the biosphere and the evolution of life forms affect the stability of global
temperature, ocean salinity, oxygen in the atmosphere and other environmental variables that affect the
habitability of Earth.

The biosphere is the biological component of earth systems, which also include the lithosphere, hydrosphere,
atmosphere and other "spheres" (e.g. cryosphere, anthrosphere, etc.). The biosphere includes all living
organisms on earth, together with the dead organic matter produced by them.
HYDROSPHERE

ATMOSPHERE

– Sea of air

Composition of air:
Nitrogen
Oxygen
Argon, Carbon Dioxide

Air is matter. It occupies space and has weight

The gases of the air are pulled by the earth’s gravity
The weight of the air above and the pull of the earth’s gravity
tend to keep most of the air molecules close to the surface of the
earth.

LAYERS OF THE ATMOSPHERE

1. Troposphere–16 to 18 km-the lowest layer

2. Stratosphere–height of 85 km; within it is the ozone layer,
which filters harmful radiation from the sun.
Ozone- 3 atoms of oxygen (O3)
3. Ionosphere–region of electrically charged particles––ions

1000km
It can reflect radio messages to earth

4. Exosphere
 6H2O + 6CO2 –––––––> C6H12O6+ 6O2

Most of us don't speak chemicals, so the above chemical equation translates as: six molecules of water plus six molecules of
carbon dioxide produce one molecule of sugar plus six molecules of oxygen (Photosynthesis)

Species—group of similarly constructed organisms capable of interbreeding and producing fertile offspring; Organisms
that share a common gene pool.
Speciation–origin of new species due to the evolutionary process of descent with modification
Natural Selection—Mechanism of evolution caused by environmental selections of organisms most fit to reproduce;
results in adaptation to the environment.
Evolution– Descent of organisms from common ancestors with the development of genetic and phenotypic changes
over time that make them suited to the environment.