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Why do so many different animals have the
same structures, the arm bones in a
human are the same bones as a flipper in
a whale?
Why are there bones and fossil evidence of
creatures that no longer exist? What
happened to these creatures?
Why do organisms have structures they no
longer use, like the appendix in a human?
Non functioning wings in penguins?
Evolution
These questions and others can
be answered by EVOLUTION
The Theory of Evolution is
considered a Unifying Theory of
Biology, because it answers many
of these questions and offers and
explanation for the data.
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.
Darwin noticed
that everywhere he
went on his
voyage, 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 called this…
descent with modification
or
(change in species over time)
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. The environment presents challenges to
survival.
There is a constant
struggle for survival.
Examples are:
Drought
Fires
Floods
Snowstorms
Hurricanes
Tornadoes
Other natural disasters
3. Organisms produce more offspring than can
survive. Competition (struggle for existence)
exists WITHIN and AMONG species.
Within a Species
Among a Species
food
food
space
space
mates
4. Survival of the fittest. Some organisms are
more suited to their environment as a result of
variation in the species.
Fitness: the ability of an individual to survive
and reproduce in its specific environment.
Fitness is a result of adaptation
Organisms who possess favorable traits will
leave more offspring.
In other words, he who spreads the
most genes wins!
1st
5. Decent with modification. Living species today are
descended with modifications from common ancestral
species.
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 long 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.
• An organism does not change because of
need or desire to survive. The organism
either already has the variation that
enables it to survive or it dies
Adaptations
• Adaptations are evidence of evolution
• Structural adaptations
Mimicry – enables 1 species to look like
another
Yellow jacket wasp
Harmless syrphid fly
Adaptations
Camouflage enables organisms to blend in
with their environment
Evidences of Evolution
Today most evidences for evolution
are grouped into five main categories:
•
•
•
•
•
Fossil Record
Biochemical
Comparative Anatomy
Biogeography
Observable Events
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
• ANALOGOUS STRUCTURES
• Body parts that do not have common
evolutionary origins but are similar in
function
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
FOSSIL RECORD
• Paleontology
• Fossil – remains or traces of an
organism that lived long ago
• Remains: ex. bone,
tooth, 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
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.