Change Over Time…….
Definition: change of species over time
Evidence of Evolution
Key Concept

Darwin Argued That Living Things Have Been
Evolving On Earth For Millions of Years.
Evidence For This Process Could Be Found In:
The Fossil Record
The Geographical Distribution of Living
Species
Homologous Structures of Living Organisms
Similarities In Early Development
DNA Comparisons –similarities in nucleotide
sequences
What is a fossil?
The preserved or mineralized
remains (bone, tooth, or shell) or
 burrow, or imprint)
traces (footprints,
of an organism that lived long ago.
Ammonite fossil (shell)
Dinosaur fossil - (bone)
Fossils are very old

Trilobite fossils
445 million years ago
Beetle fossil
50 million years old
Stingray fossil
95 million year old
Bird egg fossil
1 million years old
Fossil Record

Earth is Billions of Years Old
Fossils In Different Layers of Rock
(sedimentary Rock Strata) Showed
Evidence Of Gradual Change Over
Time
Gradualism: hypothesis that
evolution occurs at a slow, constant
rate
How do fossils form?
 Most fossils are laid down in sedimentary rock (particles carried by streams and rivers that eventually
settle to the bottom in layers)

Many fossils are
found in the
Grand Canyon
The oldest particles, and therefore the
oldest fossils will be at the bottom,
with new layers being added on top.

The deeper down you go, the simpler
the life forms are.
This leads some to believe that life
began as simple prokaryotic cells and
gradually became more complex
because…
Fossil record of the modern horse
Today
55 million
years ago

Voyage of the Beagle
Charles Darwin
Born Feb. 12, 1809
Joined Crew of HMS
Beagle, 1831
Naturalist
5 Year Voyage around
world
Avid Collector of Flora
& Fauna
Astounded By Variety
of Life
HMS Beagle

The purpose of the trip was to draw accurate
maps of the region. Darwin was to collect
specimens and document the plant and
animal life.
The Galapagos Islands

 Small Group of Islands 1000 km West of South
America
Very Different Climates
Animals On Islands Unique
Tortoises
Iguanas
Finches
Darwin’s Observations
Patterns of
Diversity were
shown
Unique Adaptations
in organisms
Species Not Evenly
Distributed
 Australia, Kangaroos,
but No Rabbits
 S. America, Llamas
Adaptation

 Process by which a species becomes better suited to
its environment
 Organisms well suited to their environment
reproduce at a greater rate than those less suited to
the same environment
 Ex: Camouflage
Darwin’s
Theory of
Evolution
•The unequal ability of individuals to
survive and reproduce leads to a gradual
change in a population, with favorable
characteristics accumulating over
generations (natural selection)
•New species evolve
Geographic Distribution
of Living Species

 Different Animals On
Different Continents But
Similar Adaptations To
Shared Environments
Darwin’s Theory of
Natural Selection

1.
2.
3.
4.
5.
There is variation within any species
All organisms tend to over-reproduce
There is a struggle for survival
The fittest survive
The environment determines who is the
fittest
1. Variation exists within
every population

Ladybugs have different spots

Zebras all have
different stripes
2.
All species tend to produce more
offspring than they can SUPPORT

Turtle eggs
Insect
eggs
Baby
mice
Frog eggs
3. There is a Struggle for
Survival

1. To eat
2. To drink
3. Territory
4. To mate
4. The fittest will
survive

4. The fittest will
survive

Healthy or sick horse?
5. Nature (the environment) will
determine which organism is the fittest
to Survive

long neck giraffes survive over short neck
giraffes.
Evidence of Natural Selection in our
lifetime

The Peppered Moth in England
Before the industrial
revolution
After the industrial
revolution
Natural Selection
Driving force for
evolution
During the struggle for
resources, strongest
survive & reproduce
Idea that at least some
of the differences
between individuals,
which impact their
survival and fertility,
are inheritable
Natural Selection

 Organisms with traits well suited to their
environments survive and reproduce at a GREATER
rate than less well-adapted organisms in the same
environment
 Causes changes in the frequency of certain alleles in
a population
When do new species form?

 Subspecies diverge
 Because of natural selection
 Members of the same species become adapted to a
new environment
Speciation: process by which new species form
http://www.youtube.com/watch?v=YCoEiLOV8jc
Supporting Evidence
Homologous Structures
Homologous Body
Structures

Scientists Noticed Animals With
Backbones (Vertebrates) Had Similar
Bone Structure
May Differ In Form or Function
Same Structure
Example: Limb Bones Develop In
Similar Patterns
Arms, Wings, Legs, Flippers
Homologous Body
Structures

 Structures That Have Different Mature Forms But
Develop From The Same Embryonic Tissues
 Strong Evidence That All Four-Limbed Animals
With Backbones Descended, With Modification,
From A Common Ancestor
 Nucleotide sequences show many similarities
 Help Scientist Group Animals
Homologous Body
Structures

Analogous Body Structures

 Body structures that have the same function
Example: All of the structures below are used for
flight
Evidence for Evolution - Comparative Embryology
Similarities In Embryonic Development
Some animals appear to have structures that
no longer serve a function –
(called vestigial structures)

Vestigial leg bones in a python
Structures
that are just
there
because of
the
evolution of
other
structures
Vestigial wings in a flightless bird
Ex a penguin and an ostrich

Human appendix is
vestigial

 The human appendix has no function in
humans but is very
important in horses
and other animals
Human tailbone is a vestigial
vertebrate tail

Human tail bone
consists of fused
vertebrae that no
longer function
as a tail
Evolutionary
Time Scales
Macroevolution:
Long time scale
events that create
and destroy
species.
Evolutionary
Time Scales
Microevolution:
Short time scale
events (generationto-generation) that
change the
genotypes and
phenotypes of
populations