Transcript Evidences of Evolution Evidences_of_Evolution_PPT

Evidences of Evolution
Evolution
Genetic change in a
population over time
Charles Darwin
On his journey around the world,
Darwin found evidence of gradual
change (evolution).
Darwin cited
evidences he found
in fossil records,
homologous
structures, and
geographic
distribution.
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- the study of fossils
• Fossils – remains or traces of
organisms that lived long ago
• Remains: ex.
bones, teeth, or
shells
• Traces: ex.
burrows, footprints,
or imprints
Fossil Record
Most fossils are found in layered
sedimentary rock
Oldest fossils are
on the lowest layer
Fossil Record
• The fossil record is incomplete
– Some environments are less likely to cause
fossil formation
– Bodies of some organisms decay faster than
others
• The fossils that have formed present
strong evidence that evolution has taken
place
– Relative and radiometric dating
Fossil Record
Comparing fossils from different layers
shows:
 Life on Earth
has changed
 Increased
number of life
forms
Biochemical Evidence
• Universal Genetic Code
– Triplets of DNA nitrogen-base sequences that
code for specific amino acids
The similarity of
triplet DNA codes
making-up amino
acids shows:
a probable
common
ancestor for all
life on Earth
Biochemical Evidence
• Amino Acid Sequencing
The amino acid
sequence in a
particular protein is
compared between
organisms.
Species that have few
differences are thought to
have shared a common
ancestor more recently.
45
27
67
1
Number of differences
from human hemoglobin
Biochemical Evidence
Amino Acid
Sequencing is
probably the
STRONGEST
evidence for
relationships
among
organisms.
Amino Acid Difference in
Hemoglobin Compared
with Human
Species
Gorilla
Rhesus Monkey
Mouse
Chicken
Frog
Lamprey
Difference
1
8
27
45
67
125
Human hemoglobin
has 146 amino acids
Biochemical Evidence
• Cladogram: diagram that shows
the evolutionary relationship
among a group of organisms.
B
A
Where
would the
What organism
common
belongs
at each
ancestor
be?
branch?
Common
ancestor
150
C
D
Species
Difference
Gorilla
1
Monkey
8
Mouse
27
Chicken
45
Frog
67
Lamprey
125
E
F
G
10 0
20
30
50 40
100
Number of Amino Acid Differences
Comparative Anatomy
• Homologous structures- structures that share
a common ancestry; similar structures with
different functions
Alligator
Turtle
Bird
Mammal
Ancient lobe-finned fish
Homologous structures
show:
an organism’s
evolutionary past
and common ancestry
Comparative Anatomy
• Vestigial structures- structures that are
present but diminished in size or function
Vestigial structures show:
• an organism’s evolutionary
past
• a common ancestor with
species that have similar
structures that are still
functioning
Examples: Human tailbone, snake pelvic bones and limb bones, and some cavedwelling salamanders have eyes even though members of the species are
completely blind.
Comparative Anatomy
• Embryology- embryos of different species
may appear similar in early stages of
development
Example: vertebrate
development
– Tail buds and
pharyngeal pouches
Comparative Anatomy
• Comparison of
similarities in
embryos can
show:
relationships to a
common
ancestor
Biogeography
• Geographic Distribution of Organisms
Beaver
Muskrat
Beaver and
Muskrat
Coypu
Capybara
Coypu and
Capybara
• Organisms living
widely apart (even
different continents)
may be similar
because they share
a common ancestor
Observable Events
• Observable events show that evolution is an ongoing
process
• 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