Download Evidence for Evolution

S&T: 3 pg. 310 give examples of types
of evidence that Darwin gathered to
develop the theory of evolution;
1.
2.
3.
4.
5.
Structural similarities among organisms.
Geographic distribution of organisms.
The embryological similarities among organisms.
The pattern of organism groupings.
The direct observation of evolutionary changes
in the laboratory and in the wild.
6. The molecular similarities among organismswere found after Darwin (more to come ).
7.Transitional species found in fossil record.-bonus
Evidence for Evolution
Key Idea
• Evidence for evolution comes from many
sources.
1. Fossils
2. Vestigial structures
3. Biogeography
4. Homologous structures
5. Embryology
6. DNA/protein sequences
Fossils
• Fossils provide evidence of
evolution.
• Fossils in older layers are
more primitive than those
in the upper layers.
• Extinct Fossils resemble
modern animals. This
shows a common
ancestry.
Dating Fossils
– Relative dating estimates the time during which
an organism lived.
– It compares the placement
of fossils in layers of rock.
– Scientists infer the order in
which species existed.
Transitional species found in fossil
record – fish-amphibian (Tiktaalik)
• 375 million years old
• Discovered in
Canada in 2004
Transitional fossil:
bird/reptile
Archaeopteryx
150 million yrs old.
7 specimens found
Fossil Evidence for Whale Evolution
Whale Video
2. Vestigial Structures
• Vestigial structures are remnants of
organs or structures that had a function in
an early ancestor.
• Examples include ostrich wings, human
appendix, and wisdom teeth, whale and
snake pelvis/hind legs.
Pythons have tiny femurs (leg
bone)
3. Biogeography
Biogeography: the study of past and present
distribution of species.
• The study of geography provides evidence of
evolution.
– island species most closely resemble nearest
mainland species
– populations can show variation from one
island to another
4. Homologous Structures
• Homologous structures- Similar anatomical
features that originated in a shared ancestor.
• Homologous structures are similar in structure
but may be different in function.
Homologous Structures vs. Analogous
Structures
• Analogous structures have
a similar function.
Mole foot
• Analogous structures are not evidence of a common
ancestor.
Human hand
Fly wing
Bat wing
Analogous Structures
look similar on the outside
 same function
 different structure & development on the inside
 different origin
 no evolutionary relationship


Solving a similar problem with a similar solution
Homologies: at the cellular level
Review from IS 1: What cellular structures are
shared by all eukaryotic organisms?
5. Embryology
• Embryology- studying the early stages of
development of an organism (inside the
womb or inside the egg)
all vertebrate embryos have a “gill
pouch” at one stage of development
Hox genes control body development in many organisms.
They help control head to tail organization.
6. DNA/Protein Sequences
• Two closely-related organisms will have similar
DNA, RNA, and protein (amino acid)
sequences.
• This also gives evidence of a common
ancestor.
 Comparing DNA & protein structure

everyone uses the same genetic code!
 DNA
Human
Macaque
Dog Bird
Frog
Lamprey
8
32 45
67
125
 compare common genes
 compare common proteins
number of amino acids different
from human hemoglobin
0 10 20 30 40 50 60 70 80 90 100 110 120
DNA (cont)
• DNA code itself is a homology that links all life on
Earth to a common ancestor.
• In some cases, if we were to transfer genetic
material from the cell of one living thing to the cell
of another, the recipient would follow the new
instructions as if they were its own.
• Useful in genetic engineering
GFP traditionally refers to the
protein first isolated from a
gene found in the jellyfish
Aequorea victoria which glows
in the dark.
• This gene can be transferred to other
organisms which will express this same trait
GloFish, the first genetically modified animal to
be sold as a pet
Building “family” trees - Phylogenies
Closely related species are branches on the tree — coming
from a common ancestor
Cladograms
• diagram that depicts evolutionary
relationships among groups.
• based on PHYLOGENY, which is the study of
evolutionary relationships.
• Uses traits/characteristics that are common
between organisms to organize them
You try: Match each point on the
cladogram with the trait.
1. ______ Wings
2. ______ 6 Legs
3. ___ Segmented Body
4. ___ Double set of wings
5. ____ Jumping Legs
6. __ Crushing mouthparts
7. ____ Legs
8. ______ Curly Antennae
Phylogenetic trees
• Very similar to a cladogram
• Tends to use genetic information and physical
traits to construct
• Root of the tree represents the ancestral
lineage, and the tips of the branches
represent the descendants of that ancestor.
• As you move from the root to the tips, you are
moving forward in time.
Speciation
• Species: a group of organisms that can
interbreed in nature
• Speciation: When two groups of organisms
can no longer interbreed – they have become
too different through evolution
• When a lineage splits (speciation – forming a
new species), it is represented as branching
on a phylogeny. When a speciation event
occurs, a single ancestral lineage gives rise to
two or more daughter lineages.
• Phylogenies trace patterns of shared ancestry
between lineages. Each lineage has a part of
its history that is unique to it alone and parts
that are shared with other lineages.
• Each lineage also has ancestors that are
unique to that lineage and ancestors that are
shared with other lineages — common
ancestors
• Nodes represent common ancestors