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Evolution
To see where we might be going, we must
understand where we have been
Robert Tamarkin, 1993
Definition?
•Theory supported by evidence
•Biological evolution concerns changes in
living organisms during the history of life on
earth.
•Sharing of common ancestors
•Darwin term: descent with modification
Branched Tree of Life
with a common
ancestor
Evidence of Evolution
Formation of the Earth
• 4.6 billion years old (dated from radiometric
dating)
• Complex: but woven out of 30ish main
molecules – oxygen, hydrogen, carbon,
nitrogen, Sulphur and phosphorus.
(evidence #1)- present in early Earth- amino
acids, RNA, DNA, Phosphorus, ATP
1. Earth is Old: Fossils
•Fossils: the remains or impression of a prehistoric
organism preserved in petrified form or as a mold
or cast in rock.
Changes begin
from simple to
more complex
Generally
older
fossils
are lower
in the
strata
First Life Form –
simple cells – fossil
evidence 3.4 billion
years ago
Fossil Record Supports Evolution
• Millions of fossils have been discovered
• Fossil record shows changes of organisms through time from simple to
more complex.
• Documents the order of appearance of groups and types of organisms
• Transitional Species show transitions from fish to tetrapods (fish to
salamanders, salamanders to reptiles), dinosaurs to birds, proto-horses to
horses , apes to human, synapsid to mammals.
• Document major crises in Earth’s history and the recovery from events.
From Land to Water
Has gills, scales, no neck
(like fish)
But – head is crocodilelike and strong hind limbs
Tiktaalik
- transition between fish
and tetrapods (four-legged)
-marks the appearance of
limbs in fish –
- lived about 12 million
years before the fist
tetrapod- 363 million years
old
From Land to Air – Archaeopteryx
Archaeopteryx
- Transition between bird and dinosaur
- Bird Like features- feathers – tail feathers, evidence of flight
- Dinosaur like features – sharp teeth, long bony tail, claws.
Oxygen Environment
• An increase in oxygen levels
• Shown by red beds – iron “rusts” or
turns red in the presence of oxygen
• Luckily- happened slowly 2.7 to 2.0 bya
• What type of organism was responsible
for an increase in oxygen?
Radiometric Dating
Radiometric Dating
*Fossils
show relative dating by comparing data in the rock
strata – relationship to each other in the layers.
*Radiometric Dating ability to use absolute dating - done
by comparing proportions of radioactive isotopes in the
sample.
* Radiometric Elements are unstable (called parents) and
they decay into different elements (daughter elements).
Uranium to lead.
http://science.howstuffworks.com/29145-100-greatest-discoveries-radiometric-datingvideo.htm
•Earth’s oldest crustal
rocks – 4.03 billion years
old.
•Oldest metamorphosed
sediment – zircon crystals
found in Canada- 4.4
billion years old.
Radiometric Dating Supports Evolution
• many naturally-occurring elements are radioactive and they break down, or
decay, at known predictable rates.
• isotope pairs are useful in dating the Earth such as rubidium/strontium,
thorium/lead, potassium/argon, argon/argon, or uranium/lead, all of which
have very long half-lives, ranging from 0.7 to 48.6 billion years.
• Subtle differences in the relative proportions of the two isotopes can give
good dates for rocks of any age.
• Dates are often cross-tested using different isotope pairs.
• Results from different techniques, often measured in rival labs, continually
confirm each other.
• Repeatable results
Natural Selection
Charles Darwin
• Not exactly a star student, but he revolutionized the
scientific view of the natural world with his Theory of
Natural Selection
• Traveled on the Beagle where his journey began in 1831
for a 5 year voyage
• The Beagle traveled from Europe to the Galapagos Islands
then to Australia around the Cape of Good Hope and
back to Europe
Observations aboard the Beagle
1. Species vary globally
a. Two similar species live in different areas of the
world
2. Species vary locally
a. Differences among tortoises in the Galapagos islands
3. Species vary overtime
a. Fossils of extinct animals looked similar to living
animals
Natural Selection
• Natural Selection:
Organisms best suited to
their environment survive
and are able to produce
offspring
• Fitness-How well an
organism can survive
• Adaptation- Any heritable
characteristic that
increases an organisms
ability to survive
Conditions Necessary for Natural
Selection
• Overpopulation- individuals in a population have a
capacity to produce more offspring than the
environment can support – leads to completion and
a….
• Struggle for existence
• Variations – size, form, speed, camouflage, strength,
horns, etc. • Those best suited (fitness of traits) to the
environment will survive and pass along their
characteristics to their offspring.
Challenge
•Describe evolution
through natural selection
in any species using terms
from last slide – pick an
adaptation
Directional Selection
• Favoring one phenotype over others –
Examples
• Darker-colored Peppered Moths in England and the
Industrial Revolution
• mouse population- brown mice on the brown forest floor.
• Antibiotic resistance in bacteria and the use of antibiotics
• Pesticide resistance in insects
Antibiotic Resistance
•Antibiotic-Resistant Mycobacterium
tuberculosis (TB)
•Methicillin-Resistant Staphylococcus
aureus (MRSA)
•Vancomycin-Resistant Enterococci
•(VRE)
•Neisseria gonorrhoeae (Gonorrhea)
•Clostridium difficile.
•Gram-negative Bacteria.
Allele Frequency Changes
Peppered Moths During the
Industrial Revolution in
England
Dark Color is Dominant
Show a change over time in
three generations following
darkening of the trees
Directional
Selection –
depends on the
Rainfall
Seed Size increases
during droughtFavors larger beaks
Stabilizing
Stabilizing – intermediate
phenotypes selected because
of a higher fitness
*Examples –
Human birth weight
Plant height
Robinstypically
lay
Four
eggs
Disruptive Selection
•Extreme phenotypes are selected for by
the environment
•Example: African Finches – Large and
small beaked birds have a higher
survival rate than intermediate
(environmental force – food availability
–large seeds and small seeds)
Think about a situation
that might result in
Disruptive selection –
what type of
environment
Artificial Selection
Artificial Selection
• Breeding of organisms (plants, animals, bacteria, etc.)
to produce desirable traits.
• Manipulated by humans
• Examples:
• Dogs for specific purpose- herding, hunting, pets, etc.
• Fruit and veggies- improved tastes, resistance to pests,
etc.
• Roses – most beautiful
• Fruit Trees- ability to survive in northern climates
Comparing anatomy
• Homologous Structure: structures that are
shared by related species and that have been
inherited from a common ancestor
Table Buddy Colaboration
•Research for 5 minutes examples of
homologous structures – list in your
notes
•Come up with a reason why
homologous structures support the
theory of evolution.- explain in your
notes.
Analogous Structures
• When the function is common but the
structure is different and example of this is
the wing of a bird and the wing of a
butterfly.
Vestigial Structures
• inherited from ancestors but have lost much
or all of their original function due to
different selection pressures acting on the
descendent
• “left-overs”
The Process of Speciation
•Species – population-members can
interbreed and produce fertile
offspring
•speciation-formation of new species
Table Buddy Collaboration
Green algae evolution to land
plant draw a
picture and explain process
Molecular Evidence
of Evolution
Other Supports
• All organism are cellular – membranes filled with
water – genetic material, proteins, lipids, carbs,
salts, etc.
• Most organisms use sugar for fuel in s similar
process
• -proteins as building blocks and messengers- same
amino acids to make them
Only three differences in plants and animal cells
Amino Acid Differences in Cytochrome c (CR)
Organism
Number of amino acid
differences
Human
Chimpanzee
0
0
Rhesus monkey
1
Rabbit
9
Pig
Dog
Horse
Moth
Yeast
10
10
12
24
38
DNA Similarities
Collaboration – One Minute Summary 
• Discuss with your table buddy what you
would like to summarize as evidence of
evolution covered in this unit – must include
examples, all evidence presented. I will have
you summarize in a 30 second to one minute
summary -
Descent with Modification
• A shared character is one that two lineages have
in common, and a derived character:
character the sets the group
Examples of derived characters
Amniotic egg, lungs, vertebral
Columns, etc.