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born in Shrewsbury,
England, in 1809
studied medicine at
Edinburgh University
(1825-1827) where the
sight of blood and
surgery without
anesthetics repulsed him
studied to become a
clergyman at Cambridge
University (1827-1831)
After Cambridge,
Charles was
recommended for a
surveying trip on the
HMS Beagle.
He sailed aboard the
Beagle for 5 years,
working as a naturalist.
The Beagle sailed around the world.
This voyage lasted from 1831 to 1836.
At the time Darwin made
his trip, the majority of
people believed the
Earth and all of its forms
of life had been created
only a few thousand
years in the past.
People also believed that the Earth had not
changed during those few thousand years.
People also believed in fixity of species; in other
words, species never changed.
The first dinosaur to be described
scientifically was Megalosaurus
by William Buckland in 1824.
After careful
observation and
study of new
scientific
discoveries,
Darwin began to
think otherwise.
The Father of Geology
Darwin was influenced
by geologist James
Hutton’s writings that
described geologic
forces he thought had
changed and were still
changing the earth.
Hutton proposed that
the Earth had to be
much more than a few
thousand years old.
Darwin was also
influenced by
geologist Charles
Lyell who wrote
Principia Geologica.
Lyell’s book proposed
that tremendous
geologic processes
had shaped the Earth
such as seen in
volcanoes active in
the present.
On the voyage,
Darwin noticed
that everywhere he
went, the animals
and plants differed
vastly.
Patterns in the species
suggested that the
species had changed
over time and had given
rise to new and different
species.
Many of Darwin’s
conclusions were
based on
observations of
wildlife in the
Galapagos Islands.
The Galapagos
Islands lie 500 miles
west of Ecuador in
the Pacific Ocean,
directly on the
equator.
“Galapagos” means turtle.
Darwin noticed on
these islands,
there were several
types of finches.
What it must have been
like to be Darwin…
In particular,
Darwin observed
something odd
about the
finches: they all
looked like a
bird he had seen
on the South
American
continent.
Darwin wondered if the birds and other
animals had been created to match their
environment, why didn’t these birds look like
the birds of the African continent, since the
environments of both the Galapagos and
Africa were similar.
Darwin guessed that
some of the birds
from South America
migrated to the
Galapagos.
Once on the islands,
the birds must have
changed over the
years.
large ground
finch
woodpecker
finch
cactus finch
This would explain the numerous species of
birds present.
Darwin concluded:
Each species has descended, with changes,
from other species over time.
Darwin called this…
Descent With Modifications
or
(change in species over time)
EVOLUTION IS
GENETIC CHANGE IN
A POPULATION
THROUGH TIME.
EVIDENCE OF
EVOLUTION
Charles Darwin
On his journey around the world,
Darwin found evidence of gradual
change (evolution).
Darwin cited
evidences he found
in fossil records,
geographic
distribution and
homologous
structures.
Evidences of Evolution
Today most evidences for evolution
are grouped into five main
categories:
•
•
•
•
•
Fossil Record
Biochemical
Comparative Anatomy
Biogeography
Observable Events
FOSSIL RECORD
• Paleontology
• Fossil – remains or traces of an
organism that lived long ago
• Remains: ex. bones,
teeth, or shell
• Traces: ex. burrow,
footprint, or imprint
FOSSIL RECORD
• Most fossils are found in layered
sedimentary rock
• Oldest fossils
are on the
lowest layer
FOSSIL RECORD
• Comparing fossils from different
layers shows:
 Life on Earth
has changed
 Increased
number of life
forms
FOSSIL
RECORD
When Whales Had Legs
BIOCHEMICAL
• THE GENETIC CODE
• Triplets of DNA nitrogen-base
sequences that code for specific amino
acids
• The amino
acid triplet is
the same in
almost all
organisms.
BIOCHEMICAL
• The similarity of triplet DNA codes
making-up amino acids shows:
 A probable common
ancestor for all life on
Earth
 Amino Acid Sequencing
is probably the
STRONGEST evidence
for relationships among
organisms.
COMPARATIVE ANATOMY
• HOMOLOGOUS STRUCTURES
• structures with similar structure but
different function
• (ex: turtle, alligator, bird, mammal)
Turtle
Alligator
Bird
Mammal
COMPARATIVE ANATOMY
• Homologous structures show
Similar genes
Descent from a common ancestor
Turtle
Alligator
Bird
Mammal
Ancient lobe-finned fish
COMPARATIVE ANATOMY
• VESTIGIAL STRUCTURES
• organs so reduced in size
that they are nonfunctioning
remnants of similar organs
in other species
• ex: human tailbone,
appendix, whale pelvis
COMPARATIVE ANATOMY
• Vestigial structures show:
an organism’s
evolutionary past
a common ancestor with
species that have similar
structures that are still
functioning
COMPARATIVE
ANATOMY
Vestigial Structures
When Whales Had Legs
COMPARATIVE ANATOMY
• EMBRYOLOGY
• Embryos of different species may
appear similar in early stages of
development
• ex: vertebrate
development
COMPARATIVE ANATOMY
• Comparison of
similarities in
embryos can
show:
Relationship to
a common
ancestor
Human embryo
BIOGEOGRAPHY
• GEOGRAPHIC DISTRIBUTION
OF ORGANISMS
• organisms living
widely apart (even
different continents)
may be similar
because they share
a common ancestor
Beaver
Muskrat
Beaver and
Muskrat
Coypu
Capybara
Coypu and
Capybara
Shows common
ancestor
OBSERVABLE EVENTS
• Some changes in species have been
observed and studied:
Peter & Rosemary
Grant’s Study of
Beak Size Shift in
Darwin’s Finches
H. Kettlewell’s Study
of Peppered Moth
Color Shifts
OBSERVABLE EVENTS
 Observable events show that evolution
is an ongoing process
Peter & Rosemary
Grant’s Study of
Beak Size Shift in
Darwin’s Finches
H. Kettlewell’s Study
of Peppered Moth
Color Shifts
Darwin based his theory
on his own observations
and the writings of
Thomas Malthus.
Malthus was a British
social scientist who
made these observations
about humans:
People have more children than are
able to survive.
There are built-in population checks:
disease, famine, and war.
Darwin extended these
principles to biology, which
helped him form his theory of…
…or Survival of the Fittest.
Five basic components of
1. All species have genetic variation.
Every species is different,
even within itself.
Look around you…are
you all the same?
2. Organisms produce more offspring than can
survive. Many that survive do not produce
offspring.
The female green sea turtle lays a clutch of about
110 eggs. She may lay several clutches.
It is likely that less than 1%
of the hatchlings will ever
reach sexual maturity.
3. Since more organisms are produced than can
survive, there is competition (struggle for
existence).
Competition exists WITHIN and AMONG species.
Within and Among Species for
food
water
shelter
space
And Within a Species for
mates
The constant struggle for survival is affected by
short-term natural disasters. (drought, fires,
floods, snowstorms, hurricanes, and tornadoes)
The constant struggle for survival
is also affected by long-term
changes in the environment. (ice
ages, biome shifts, etc)
4. Survival of the fittest Some organisms are
more suited to their environment as a result of
variations in the species.
Fitness: the ability of an individual to
survive and reproduce in its specific
environment. Fitness is a result of adaptations.
Individuals that are fit to their environment
survive and leave more offspring than those
who aren’t.
He who spreads the most genes wins!
1st
5. Decent with modification: Living species today
are descended with modifications from common
ancestral species that lived in the past.
Characteristics of fit individuals
increase in a population over time.
Over time, genes for less
favored characteristics will be
eliminated from the gene pool.
Example: giraffes and their
increasingly longer necks.
Natural Selection: Survival of the
Fittest
An adaptation is any inherited characteristic (a
genetic variation) that can increase an
organism’s chance of survival.
variation exists
An the
organism
doesfirst.
not change
because of need or desire to
the environment changes.
survive. The organism either
already
hasmay
thegive
variation
that
a variation
an advantage
toenables
survive environmental
change.
it to survive
or it dies.