Theory of Evolution
Slow Change over time
I. Fossil Record
A. The fossil record of Earth shows
evidence that species of living things
have undergone perpetual changes,
caused by changes in gene frequency.
B. Changes in gene frequencies ☞
new species
C. E.g. Evolution of the modern
horse
From Eohippus
(5 toes, > 1 foot,
size of a cat)
To Equus
(1 toe,
5 feet or more
at the withers)
E.g. Evolution of the modern
horse
D. Charles Darwin
1. Circa 1840, Charles Darwin sailed
around the world for 5 years on
the HMS Beagle.
2. Voyages of the HMS Beagle
Penguin
3. He observed great
biodiversity.
a. E.g. Birds
Blue-footed booby
Albatross
Frigate bird
Galapagos dove
b. Finches
c. Reptiles
Galapagos
tortoise
Marine iguana
d. Plants
Capparidaceae
Button mangrove
Achupalla plant.
Beach morning
glory
Passion flower
Aristolochia
Lava cactus
4. Darwin’s observations lead to…
a. Ideas to try
explain what he had
seen.
b. Publishing of
“The Origin of the
Species”
5. Ideas contributing to the
theory of evolution
a.Evolution = slow change over time,
sometimes causing new species to emerge
b. Species = a group of organisms that :
 look very much alike
 share a common ancestry
 are capable of breeding and producing viable
offspring that are capable of reproducing
b. Species
 E.g.
all dogs, same species
 However,
horse + donkey = mule
c. Natural selection
i. Species’ members survive if they have
the genes that are best suited for the
current environmental conditions.
ii. Species unable to adapt to the current
conditions become extinct.
c. Natural selection
iii. Nature selects “for” advantageous
traits (genes) and ”against” traits that
do not improve a species’ chances of
survival.
iv. Individuals with advantageous traits
survive to breed and pass those traits
to the next generation.
c. Natural selection
v. Gene frequency changes are caused by
natural selection.
vi. Natural selection may lead to
evolutionary change.
vii. The Peppered Moth
(an example of natural selection)
Light Form of peppered moth
vii. The Peppered Moth
Facts:
 Pre-Industrial revolution (late
18th & early 19th Centuries),
ratio of light peppered moths to
melanic (dark) was 50:50
Light and melanic (dark) forms
vii. The Peppered Moth



Industrial Revolution,
coal burning by
factories caused tree
trunks to become
dark- colored.
Bird predators ate
more light moths,
more melanic moths
survived.
# light moths <
# Melanic moths
g. The Peppered Moth
 By
the 1950’s, coal burning
stopped.
 Ratio of light to melanic returned
to 50:50.
 Moths did NOT change color.
 Both colors always existed in the
gene pool.
 Gene frequencies changed.
4. Adaptation
=
an anatomical structure,
physiological process, or
behavioral trait that
improves an animal’s
fitness for survival
5. Common descent
=
all life forms
come from
some
original
life form;
closely related
species have a
common
ancestor
6. Homology
a. = similarity of organisms due to
common embryonic or
evolutionary origin
b. E.g. a vertebrate forelimb
could be an arm, a wing, or a
flipper


made of same bones
may have different f(x)s
c. Homologous structures
humerus radius & ulna
metacarpals
carpals
bat
mole
human
whale
bird
horse
7. Adaptive Radiation
= production of ecologically diverse
species from a common ancestral
stock
(see text figure 1.17)
8.Extinctions
 AT
LEAST five major extinctions
in geological time
 ¿ 65 million years ago during the
Cretaceous era, what animal
group become extinct?
 ¿Why?
8. Extinctions
 Dinosaurs.
Unable
to adapt to the
changing
environmental
conditions (did not
have the gene
combinations to
permit their
survival
E. Rapid evolution?
1. Antibiotic use creating “super
germs”
2. Use of pesticides creating
“super bugs”