Download Evidence Supporting Evolution

2006 Fossil Discovery of Early Tetrapod
“Tiktaalik”
“missing link” from sea to land animals
Evidence Supporting Evolution
AP Biology
Evidence for Evolution
• Paleontology – fossils show change in a species
•
•
over time
Biogeography – Similar species are found in
similar ecosystems around the world
Morphology – Comparing structures
–
–
Homologous structures – body parts with
similar structure but possible different function.
Shows common ancestry
Analogous structures – similar structure
develops in organisms that share a common
ecosystem but not a common ancestry
• Biochemical or Molecular AP Biology
–
Similarities in gene sequences, proteins, DNA
Fossils
 Preserved remains of living things
 Paleontology is the study of the fossil

record
Most organisms do not leave a fossil after
death

Explains the “missing links”
 Sedimentation Fossils

AP Biology
As the organism decomposes the
spaces will be filled with the minerals
from the silt
The Archaeopteryx Fossil
Reptilian Features
Forelimb has three
functional fingers
with grasping
claws.
Lacks the
reductions and
fusions present in
other birds.
Breastbone is small
and lacks a keel.
True teeth set in
sockets in the jaws.
The hind-limb girdle
is typical of
dinosaurs, although
modified.
Long, bony tail.
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Avian Features
Vertebrae are
almost flatfaced.
Impressions of
feathers attached
to the forelimb.
Belly ribs.
Incomplete fusion
of the lower leg
bones.
Impressions of
feathers attached
to the tail.
LEFT: Archaeopteryx lithographica
Found in 1877 near Blumenberg, Germany
How old is that fossil?
 Relative Dating

Age of fossils based according to their location
in strata
 Absolute Dating

Age of fossils determined by analyzing the
content of radioactive isotopes found in the
fossil.
Half-life: The length of time required for half of the
radioactive elements to change into another stable
element.
Unaffected by temperature, light, pressure, etc.
All radioactive isotopes have a dependable half life.
Ex: C14 decays into N14
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Relative Dating
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Absolute Dating
How radioactive
“naturally
occurring”
elements get inside
an organism:
A.K.A –
Radiometric dating
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Homologous Structures
Anatomical evidence
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Analogous structures
Convergent
Don’t
be fooled
by evolution
their looks!
Those
tails
Does fins
this &
mean
& sleek
they bodies
have a are
recent
common
ancestor?
analogous
structures!
Solving a similar problem with a similar solution
AP Biology
Molecular Homology
Human
Macaque
Dog Bird
Frog
Lamprey
The sequence in
DNA
proteins
Why &compare
is a &molecular
DNA
proteins
record
of evolutionary
across
species?
relationships.
Comparative hemoglobin structure
8
0
32
45
67
125
10 20 30 40 50 60 70 80 90 100 110 120
Number of amino acid differences between
hemoglobin (146 aa) of vertebrate species and that of humans
AP Biology
Vestigial organs
Why would whales
have pelvis & leg bones
if they were always
sea creatures?
AP Biology
These are
remnants of
structures that were
functional in
ancestral species
Evolution evidence at the cellular level
 Domains: Archaea, Bacteria and
Eukarya

Elements conserved through all: DNA,
RNA and many metabolic pathways.
 Eukaryotes – core features:
Cytoskeleton
 Nucleus
 Membrane-bound organelles
 Linear chromosomes
 Endomembrane system

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