EVOLUTION
Evidence of Change
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Evolution:
The process by which modern
organisms have descended from
ancient organisms
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Charles Darwin

First published his book “Origin of the
Species by Means of Natural
Selection” in 1859.
.
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In this book, he
explained that if
you look back
far enough in
time, you would
see that all
species have a
common
ancestor. He
called this the
principle of
Common
Descent.
He also explained that
because of the
VARIATION that
naturally occurs within
species, some
individuals will have
more FITNESS to
survive than others.
Those individuals will
have a better chance
of REPRODUCING,
and passing on the
advantageous
GENES.
 He called this process
ADAPTATION.

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http://www.hww.ca/hww2.asp?id=94
The mountain sheep is very agile, it
has high ability to climb steep
terrain
How does a
longer neck help
a giraffe adapt
to its
Birds keep track of 7 others
environment?
-gives them ability to stay close together
http://www.gla.ac.uk/~gbza22/jpegs/birds/starling.jpg
http://www.youtube.com/watch?v=YadP3w7vkJA&feature=related
Adaptations
Inuit people, who
live in the extreme
cold of the Arctic,
have short, stout
bodies that
conserve heat.
Plant adaptations
Venus Fly Trap
 Captures animals
 Acquires minerals
for photosynthesis
An example: Bird vocalization

Birds call/sing to
◦ Attract mates
◦ Defend their territory
Songbird
Cawing crow
Owl hoots

Reid et al. (2005) used 20 years of
data from song sparrows on Mandarte
Island, B.C., Canada

Result: males with larger song
repertoires contributed more offspring
and grand-offspring to the population
◦ This was not because females mated to
males with larger repertoires laid or
hatched more eggs
◦ Rather, these males (1) lived longer; and
(2) reared a greater proportion of hatched
chicks to independence
http://209.85.173.104/search?q=cache:FQlkM9-WVrIJ:www.sjsu.edu/faculty/fry/123/birdsong2.pdf+bird+songs,+fitness&hl=
en&ct=clnk&cd=3&gl=ca
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Where is the evidence?
1.
2.
3.
4.
Fossil evidence (palaeontology)
Radioactive dating in sedimentary
rock (stratigraphy)
Comparative embryology
Comparative biochemistry
EVIDENCE OF EVOLUTION IN
STONE

Hutton and Lyell proposed that Earth
was very old and had changed slowly
and gradually over time.
James Hutton
Charles Lyell
FOSSILS:
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Geologists have
discovered
fossils of organisms
that no longer EXIST,
but have very similar
CHARACTERISTICS
to present-day
species.

Many of these fossils could be compared and
placed in a plausible SEQUENCE of change from
ANCIENT organisms to the present day. This isn’t
proof, but it is a piece of EVIDENCE.
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Fossils are formed
along with
SEDIMENTARY
rock. Sometimes,
parts of organism’s
bodies are
PRESERVED.

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Other times, rock
forms around the
HARDER parts of the
dead organisms, (the
BONES, WOOD,
SHELLS) and it
creates a bit of a
MOLD. The
ORGANIC material
from the bodies will
eventually be
REPLACED by
harder, longer lasting
INORGANIC
compounds inside
those “molds”. They
call this process
PETRIFICATION.

Fossilization is a
tricky process,
requiring VERY
SPECIFIC
CONDITIONS, and
so the fossil record
has to be put
together like a
PUZZLE that
has many broken
and lost pieces!
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Cambrian
Fossil succession
of the Trilobite
genera
Ordovician
Silurian
Devonian
Wherever these fossils
are found they always
occur in the same
succession.
http://cache.eb.com/eb/image?id=46897&rendTypeId=4
http://www.geocities.com/mrbbug1/meso4.jpg
Discovery of fossils
Some of the fossils resembled living
organisms; others did not
The Fossil Record
Most fossils are found
in sedimentary rock
What are sedimentary rocks?
◦ Rock that forms when grains of eroded rock and
other materials are carried to the bottom of a
body of water and build up under pressure into
layers
http://www.ucmp.berkeley.edu/education/explorations/tours/stories/middle/C7.html
B. Sedimentary Rocks and
Geology
 Using the LAW OF
SUPERPOSITION
geologists can find the
RELATIVE date of
fossils.
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
The law states that
the LOWER layers
of SEDIMENTARY
rock are OLDER
than the upper
layers. Fossils
found in the layers
of rock are the
same RELATIVE
AGE as the rock
itself.

Through
RADIOACTIVE
DATING geologists
are able to tell the
ABSOLUTE age of
some preserved bones
that have been
uncovered, or
determine the absolute
age of some of the
ELEMENTS that are
found in the IGNEOUS
rocks surrounding the
fossils.

Using RADIOACTIVE DATING, geologists have calculated
that the Earth is about 4.5 BILLION years old.
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The fossil
record shows
us that
change
happened
first on the
EARTH, and
then change
in the
organisms
FOLLOWED.
2. EVIDENCE IN
COMPARATIVE EMBRYOLOGY
When you compare
EMBYROS of
several species in
an EARLY STAGE
of their
development, they
are very SIMILAR
in APPEARANCE.
Later, the
EMBRYOS look
vastly DIFFERENT.
Why?
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
The theory of EVOLUTION explains these different
animals had a COMMON ANCESTOR that passed
down the sequence of developmental GENES. As
the animals evolved, they added steps to the
developmental sequence.
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3. Evidence in Comparative
Anatomy

Many species have HOMOLOGOUS structures –
body parts that have very similar INTERNAL
structure but they have different FUNCTIONS.
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
Homologous structures: parts of
different organisms, often quite
dissimilar, that developed from the
same ancestral body parts.
Bird
Wing
Porpoise Flipper

Homologous structures: body parts that
have very similar internal structure but
they have different functions
Bird
Wing
Porpoise Flipper


Examples include:
human arm and BAT
WINGS
human arm and
WHALE FLIPPERS
One of the classic examples of
a homologous structure is the
pentadactyl
(= five digit) limb.
VESTIGIAL STRUCTURES

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There are also
many VESTIGIAL
structures – body
parts present that
are similar to those
of other organisms,
but are NO
LONGER USED.
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Examples include:
HUMAN
APPENDIX
 SNAKE LEGS

Wisdom teeth
Cassowary
Male breast tissue and nipples
Human tail bone

The wings on flightless birds (e.g. The cassowary)
◦ Wings of a bird are adapted for flight
◦ Not completely useless, use for balance during running

Human tail bone (coccyx)
◦ Fused vertebrae, only vestige left of tail that other animals
use for balance, communication, (for some primates as a
prehensile limb)

Wisdom teeth
◦ Human jaw got smaller over time
◦ How may have it been beneficial to our ancestors?

Male breast tissue and nipples
◦ Was man descended from a woman? No! During early
stages of fetal development a fetus is sexless. Later in
development testosterone causes sex differentiation.
◦ A small number of men have been able to lactate.

Cancer can grow on male and female breast tissue
Hind leg bones in whales
Whiptail lizards

Fake sex in virgin whiptail lizards (vestigial
behaviour)
◦ Only females exist in several species of lizards
◦ Reproduce by parthenogenesis (unfertilized egg
develops into a new individual, forming clones of
themselves)
◦ They still try copulating, though futile

Hind leg bones in whales
◦ Biologists believe that for 100 MYA the only
vertebrates on Earth were water-dwelling
creatures with no arms or legs
◦ The “fish” began to develop hips and legs,
eventually able to walk out of water
◦ Land dwelling creatures evolved, some mammals
moved back into water (50 MYA) ancestors of
modern whales
◦ Traces of hind legs—can be seen even now.
The Sexual Organs of Dandelions
The Blind Fish Astyanax Mexicanus

Sexual organs of dandelions
◦ Like many flowers that have proper organs (stamen and
pistil) for sexual reproduction, but do not use them
◦ Instead, they make clones of themselves
◦ Asexual reproduction can be a good strategy in an
environment that is constant, if species are well suited

Blind fish
◦ Species of fish dwell in caves deep underground off the
coast of Mexico; they cannot see
◦ Has eyes, but as they develop in egg, their eyes
degenerate
◦ Born with collapsed remnant of eye covered by a flap of
skin
◦ Fish of the same species that live directly above the blind
fish, near the surface where there is plenty of light, have
functioning eyes
◦ Scientists have removed lenses from surface water fish,
implant them into blind eye fish, can develop functional eye
with pupil, cornea, and iris.
Human appendix
Biologists believe it is
a vestigial organ left behind
from a plant-eating
ancestor
Snakes “legs”

**do not confuse HOMOLOGOUS structures with
ANALOGOUS structures – ANALOGOUS structures
have a similar FUNCTIONS but have very different
INTERNAL structure.
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Bird Wing
Fly wing
EXAMPLES: Bird Wings and FLY WINGS
Analogous: Whale fin and
Fish Fin
Comparative anatomy structures
Analogous:
1. Different
ancestors
2. “analogy”=like
3. Different
underlying
structures
4. Same Function
5. Similar
Environments
Homologous:
1. Same ancestor
2. “homo”=same
3. Same underlying
structures
4. Different
Functions
5. Different
Environments
Comparative Biochemistry
Almost all living
organisms use the
same basic
biochemical
molecules,
including DNA, ATP
and many enzymes.
 In fact, molecules
such as
hemoglobin have
been used to
determine how
distantly related
some species are. http://www.sciencecollege.co.uk/SC/biochemicals/haemoglobin.j
pg

Haemoglobin is the iron-containing protein attached to red blood cells that
transports oxygen from the lungs to the rest of the body

The greater the number of
differences in the molecule, the more
distantly related the organism are.
http://newsimg.bbc.co.uk/media/images/42343000/gif/_42343831_evolution_tree_2_416.gif
Comparative Biochemistry

similar DNA
sequences=
similar gene
segments of the
DNA

Code for similar
traits in closely
related species
NATURAL VARIATION
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