Evolution
Evolution
The Universe formed
13.7 GYA as a product of
the “Big Bang”.
• The Solar
system formed
4.6 GYA
Our Sun is a Star
• Its life span is
approximately 10
billion years…. Our
star has 5 billion
years left.
Jean Baptiste Lamarck
• Published his
Theory of Evolution
in 1809.
• Proposed that Life
changed from
simple to complex
over time.
According to Lamarck
Fossils were the remains of past life
forms.
Lamarck’s Mechanisms
1. Use and Disuse
Body parts used to survive become larger
and stronger.
Body parts not used to survive deteriorate.
Lamarck’s Mechanisms
2. Acquired Characteristics
Modifications acquired by use/disuse were
passed on to offspring.
Lamarck’s Mechanisms
3. Natural Transformation of Species
….species change with every generation.
Problems with Lamarck’s Theory
• No knowledge of genetics.
• Acquired traits are not transmitted offspring.
To Lamarck’s Credits
• Did suggest correctly the role of fossils in
evolution.
• Did suggest that adaptation to the
environment is a primary product of
evolution.
James Hutton (geologist)
Gradualism - 1795
• Gradualism is the idea that changes to
the Earth’s surface is the cumulative
product of a slow, but continuous
processes.
Result
• Changes on the earth were gradual, not
catastrophic.
Charles Lyell
Uniformitarianism
• Incorporated
Hutton’s
gradualism into a
theory called
Uniformitarianism.
Uniformitarianism
• Geological processes have operated at
the same rate over the Earth’s history.
Result
• The Earth must be VERY old. (much
older than 6000 years of the fixed
species concept).
• Idea that slow and subtle processes,
such as volcanoes, erosions and
earthquakes can cause substantial
change to the Earth’s surface.
Thomas Malthus
1798 and 1826
• Malthus's idea of man's "struggle for
existence" had an influence on
Darwin's theory of evolution….. This
struggle for existence of all creatures
provides the catalyst by which
Natural Selection produces
the "survival of the fittest“.
Origin Theories Before Darwin
• The prevailing worldview, before Darwin’s ideas took
hold, was that the earth was very young, species did
not change, and the intricate features we now call
adaptations were designed by a Creator. This
worldview had held for about 2,000 years, since the
time of Aristotle.
Charles Darwin
(1809–1882) was the most
influential contributor to our
current ideas about evolution.
His book, On The Origin of
Species, written in 1859,
described evidence for
changes in species over time
and presented a mechanism,
natural selection, for how
these changes occurred.
Darwin - 1859
• Publication of
"The Origin of
Species”
“The Origin of Species”
• Documented the occurrence of evolution.
• Suggested that the mechanism for
evolution was Natural Selection.
Comment
• Darwin is best remembered for the
theory because of his overwhelming
evidence.
Voyage of the Beagle
In 1831, Charles Darwin began a 5-year voyage around the world
as a naturalist on the HMS Beagle. What he saw on that trip had a
tremendous influence on his ideas about the natural world. In
particular, he saw the organisms on the Galapagos Islands as
examples of descent with modification, which was Darwin’s term
for evolution.
Darwin's had two evolutionary
ideas...........they were "descent with
modification" and "modification by
natural selection".....
explain both and give an example
both.
Descent with Modification
Evolution is defined as descent with
modification from a common ancestor.
Evolution only occurs when there is a
change in gene frequency within a
population over time. These genetic
differences are heritable and can be
passed on to the next generation.
The central ideas of evolution are that life
has a history—it has changed over
time—and that different species share
common ancestors.
• On the next slide, you can explore
how evolutionary change and
evolutionary relationships are
represented in “family trees,” and
how these trees are constructed. You
will also find a timeline of
evolutionary history and information
on some specific events in the history
of life: human evolution and the origin
of life.
Natural Selection
Natural selection is one of the basic
mechanisms of evolution.
Darwin’s idea of evolution by natural
selection is relatively simple but often
misunderstood…. It is composed of 4
ideas: 1.) variation in traits, 2.) differential
reproduction, 3.) heredity, and 4.) the end
result.
To find out how
“Natural Selection”
works, imagine a population
of beetles:
1. There is variation in traits.
For example, some beetles are green and
some are brown.
2. There is differential reproduction.
Since the environment
can’t support unlimited
population growth, not all
individuals get to
reproduce to their full
potential. In this example,
green beetles tend to get
eaten by birds and survive
to reproduce less often
than brown beetles do.
3. There is heredity.
The surviving brown beetles have brown
baby beetles because this trait has a
genetic basis.
4. End result
The more advantageous
trait, brown coloration,
which allows the beetle
to have more offspring,
becomes more common
in the population. If this
process continues,
eventually, all
individuals in the
population will be
brown.
If you have variation, differential
reproduction, and heredity, you
will have evolution by natural
selection.
Evidences of Evolution
1. Fossils
2. Biogeography
3. Homologous and Analogous Structures
4. Vestigial Structures
5. Biochemical Similarities
Fossils
are the remains or traces of once living organisms.
Molds are fossils which formed Casts are fossils which are
from an impression of the shape formed when sediments fill
or tracks of an organism. in the cavity left by
decomposing organisms.
Fossils can be used to
1. Show the course of natural selection…
how organisms change overtime.
2. Fossils can tell us a great deal about
an organism’s surroundings and the
conditions under which it lived.
3. Certain parts of certain fossils can tell us
about growth, injury, disease, form,
function, activities, and instincts.
Preserved Bones
Bones can tell us a great deal about the area where the muscle
attaches to the bone and leaves marks that indicate size, shape,
and functions of these varied organs.
An example of this kind of
fossilization is petrified wood.
Amber is fossilized resin of a coniferous tree.
Fossils that are preserved in amber give us information about
the anatomy of that organism; since the organisms that are
preserved in amber, mostly insects, are usually preserved intact
without any disintegration of organs, muscles, and coloring.
• The cavities and the channels in skulls give
us an idea of intelligence, behavior, and their
principle features.
Dating of Fossils
• The two methods of Dating fossils are:
• 1. “Relative” Dating
And
• 2. “Absolute” Dating
Relative Dating
Using the Law of
Superposition (successive
layers of rock were deposited
one on top the other)
scientists can estimate the
“Relative” age of a fossil.
Fossils are approximately the
same age as the layer they are
found in.
The younger fossils are found
closer to the surface, the
older fossils are found in the
deeper layers.
Grand Canyon
250 million years old
255 million years old
260 million years old
265 million years old
285 million years old
Absolute, or Numerical Dating
using Radioactive Isotopes to determine the age of a sample.
To Determine the Age of the
Earth Scientists use
Radiochronometry
(The use of radioactive
isotopes to determine the age
of rocks)
Radioactive isotopes:
are atoms with too many, or, not
enough neutrons to stabilize their
nucleus…. As a result the nucleus
“decays”.
Atomic Structure
• Atoms have Atomic numbers and Atomic masses
(amu)
• Atoms can be identified by their atomic numbers
• If you change the number of protons in the
nucleus, you change the atom.
• Atomic number of Hydrogen : 1
• Atomic number of Helium: 2
• Atomic number of Gold : 79
• Atomic number of Lead: 82
• Atomic number of Uranium: 92
• Atomic number of Plutonium: 94
Types of Radioactive Decay
Alpha Radiation, Alpha
Particles are composed
of 2 protons and 2
neutrons…. a He nuclei
• Beta Radiation, Beta
particles are high
energy electrons
• Gamma Radiation,
Gamma rays are high
energy photons
Parent Element Daughter Element Half-life
• 238 U 206 Pb: 4.51 Gyr
• 235 U 207 Pb: 710 Myr
• 87 Rb 87 Sr: 50 Gyr
• 40 K 40 Ar: 1.30 Gyr
Earth’s oldest rock
Rock solidified 4.3
billion years ago
How Carbon-14 Dating Works
• Carbon-14 dating is a way of determining the age of certain
fossils up to about 50,000 years old. It is used in dating things
such as bone, cloth, wood and plant fibers. Carbon-14 dating
can only be used to date fossils which were once alive.
How Carbon-14 is Made
Cosmic rays enter the earth's
atmosphere in large numbers
every day. For example, every
person is hit by about half a
million cosmic rays every hour.
It is not uncommon for a
cosmic ray to collide with an
atom in the atmosphere,
creating a secondary cosmic
ray in the form of an energetic
neutron, and for these energetic
neutrons to collide with
nitrogen atoms. When the
neutron collides, a nitrogen-14
(seven protons, seven
neutrons) atom turns into a
carbon-14 atom (six protons,
eight neutrons) and a hydrogen
atom (one proton, zero
neutrons). Carbon-14 is
radioactive, with a half-life of
about 5,730 years.
Carbon-14 in Living Things
• The carbon-14 atoms that cosmic rays create
combine with oxygen to form carbon dioxide, which
plants absorb naturally and incorporate into plant
fibers by photosynthesis. Animals and people eat
plants and take in carbon-14 as well. The ratio of
normal carbon (carbon-12) to carbon-14 in the air
and in all living things at any given time is nearly
constant. Maybe one in a trillion carbon atoms are
carbon-14. The carbon-14 atoms are always
decaying, but they are being replaced by new
carbon-14 atoms at a constant rate. At this moment,
your body has a certain percentage of carbon-14
atoms in it, and all living plants and animals have the
same percentage.
Dating a Fossil
• As soon as a living organism dies, it stops taking in
new carbon. The ratio of carbon-12 to carbon-14 at
the moment of death is the same as every other
living thing, but the carbon-14 decays and is not
replaced. The carbon-14 decays with its half-life of
5,730 years, while the amount of carbon-12 remains
constant in the sample. By looking at the ratio of
carbon-12 to carbon-14 in the sample and comparing
it to the ratio in a living organism, it is possible to
determine the age of a formerly living thing fairly
precisely.
• Because the half-life of carbon-14 is 5,730
years, it is only reliable for dating objects up
to about 60,000 years old. However, the
principle of carbon-14 dating applies to other
isotopes as well. Potassium-40 is another
radioactive element naturally found in your
body and has a half-life of 1.3 billion years.
Other useful radioisotopes for radioactive
dating include Uranium -235 (half-life = 704
million years), Uranium -238 (half-life = 4.5
billion years), Thorium-232 (half-life = 14
billion years) and Rubidium-87 (half-life = 49
billion years).
Biogeography
Biogeography is the
study of the distribution
of fossils and living
organisms. The
distribution of fossils
indicate the continents
were once part of a
single super-continent
known as Pangea
•
Changes to the
Crust of the Earth
Edge-on View of Crust
Continent
Sea Floor 6 miles
25 miles
Convection Currents
Plate Tectonics
Theory that the Earth’s Crust is Broken into moving Plates.
Some of the Major Plates
Convection currents
in the Mantle are
responsible for
moving the various
plates.
The Edges of the Plates are areas of Intense Geologic
Activity, such as Earthquakes, Volcanoes an Mountain
Building.
Transform Zone: one Plate slips by an adjacent Plate
San Andreas Fault
North American
Plate
Pacific Plate
San Andreas Fault
Approximately 1
million years
from now the
“Bay-Bridge”
series (baseball)
will be between
San Francisco
and Los Angeles.
“Homologous” Structures
and
"Analogous" Structures
Homologous Structures in Animals
Homologous Structures are body parts which resemble one another in
different species because they have evolved form a common ancestor.
Homologous structures may look different because the anatomy is modified
to live in different environments.
Analogous Structures in Animals
BAT BIRD
Analogy of bat & bird wings
• Analogous structures are body parts that resemble one another in different
species, not because they have evolved form a common ancestor, but
because they evolved as adaptations to their environment. Wings of bat and
wings of a bird are analogous because they are both adaptations for flying.
The fins of a whale and the fins of a shark are also analogous because they
are both adaptations for swimming.
“Vestigial Structures”
are functionless structures that were once functional in ancestral species.
This is a skeletal
view of what
would be the
pelvic region of a
boa - a large
snake. Snakes
obviously do not
have legs, yet
these boas have
the vestigial
remnants of both
pelvic girdles and
limbs, complete
with a
rudimentary claw.
• In the illustration above, the coccyx or "tail-bone" of a human is shown. It is a
much-shortened version of the tail present in most mammals. The tail is also
equipped with vestigial muscles and nerves, yet it is short, rigid, contained
completely within the body in most people, and completely non-functional!
Other examples of such structures in humans include the appendix, wisdom
teeth, and the muscles to used move the ears. In the case of the appendix and
wisdom teeth, the structures are not only non-functional, but they have the
potential for serious infection or even death.
Biochemical (macromolecule) Similarities
and
Molecular Evolution
• For evolutionists the revolution in DNA technology has been a
major advance. The reason is scientists can determine the
nucleotide and amino acid sequences of DNA and proteins form
different species. Closely related species share a higher
percentage of sequences than species distantly related.
• More than 98% of the DNA sequences in humans and
chimpanzees are identical…..did we evolve from
chimpanzees?...of course not….if we did there would no longer
be chimpanzees…….however, there is strong evidence that we
share a common ancestor.
What is a Species?
A species is often defined as a group of individuals that actually
or potentially interbreed in nature.
For example, these happy face spiders look different, but since
they can interbreed, they are considered the same species:
Theridion grallator.
Speciation
Speciation is a lineage-splitting event that produces two or more
separate species. Imagine that you are looking at a tip of the tree of life
that constitutes a species of fruit fly. Move down the phylogeny to
where your fruit fly twig is connected to the rest of the tree. That
branching point, and every other branching point on the tree, is a
speciation event. At that point genetic changes resulted in two
separate fruit fly lineages, where previously there had just been one
lineage.
The branching points on
this partial Drosophila
phylogeny represent long
past speciation events.
Adaptive Radiation
• An adaptive radiation generally means
an event in which a lineage rapidly
diversifies, with the newly formed
lineages evolving different adaptations.
Different factors may trigger adaptive
radiations, but each is a response to an
opportunity. These include:
The evolution of a key adaptation
A key adaptation usually
means an adaptation that
allows the organism to
evolve to exploit a new
niche or resource. A key
adaptation may open up
many new niches to an
organism and provide the
opportunity for an adaptive
radiation. For example,
beetle radiations may have
been triggered by
adaptations for feeding on
flowering plants.
Release from competition/vacated niches:
Lineages that invade islands may give rise to adaptive radiations
because the invaders are free from competition with other species. On
the mainland, other species may fill all the possible ecological niches,
making it impossible for a lineage to split into new forms and diversify.
On an island, however, these niches may be empty. Extinctions can also
empty ecological niches and make an adaptive radiation possible. For
example, open niches vacated by dinosaur extinctions may have allowed
mammals to radiate into these positions in the terrestrial food web.
Specialization:
Specialization may subdivide
a single niche into many new
niches. For example, cichlid
fishes have diversified in East
African lakes into more than
600 species. This
diversification may have been
possible because different
fish lineages evolved to take
advantage of different foods
(including insects, algae,
mollusks, small fish, large
fish, other fishes’ scales, and
even other fishes’ eyes!).
Genetic Drift
• Changes in the gene pool of a small
population by chance.
By Chance
Convergent Evolution
Even though fish are not at all
closely related to whales and
dolphins, they look very similar. Both
groups have pairs of fins, a tailfin
and a streamlined form. Since these
characteristics are extremely
successful for animals living in the
water, these groups evolved along
the similar lines. This is known as
convergent evolution - i.e. similar
characteristics evolving as the result
of living in similar environmental
circumstances. Wings are another
example of convergent evolution;
they can be found in birds, bats and
insects, and these animals are not at
all closely related!
Divergent Evolution
Divergent Evolution occurs
when one species evolves
into two (or more) species,
which continue to change
over time and become less
and less alike.
Coevolution
Coevolution is the evolution of one
species in response to new
adaptations that appear in another
species.
• Pollination of many of flowers occurs as a result of the
coevolution of finely-tuned traits between flowers and their
pollinators.
Yucca tree flowers have coevolved with moths who roll the pollen into balls
and carry it to another Yucca tree deposit it on the stigma.
Pollination of many of flowers occurs as a result of the
coevolution of finely-tuned traits between flowers and their
pollinators.
Red, tubular flowers have coevolved with hummingbirds who have long beaks
and are attracted to red.
By studying inherited species' characteristics and other historical
evidence, we can reconstruct evolutionary relationships and
represent them on a "family tree," called a phylogeny.