Evolution
A population changes over time
Charles Darwin (1809- 1882)
A. Published Origin of Species in 1859
- 22 years old, HMS Beagle
- Voyage of 5 years
2. Galapagos Islands
B. Darwin’s Influences
1. Lamarck (early 1800s)
i. Believed that
animals
change over
timecontrary to
popular
belief!
ii. Inheritance of Acquired Characteristics:
characteristics can be gained through use and passed on to
offspring
Kayan “giraffe” women
Traits Must be Genetic to Pass
On!
 You cannot “ force” yourself to have a
characteristics
 Example #1: You cannot force yourself to be
lactose tolerant
 Example #2: Bacteria CANNOT acquire
resistance to antibiotics
Note: New traits cannot be created during your
lifetime
Only genes can be passed on
2. Lyell
• Previously, idea was that Earth itself is less than 10,000 years old
• Proposed that gradual and observable geologic processes such as
erosion could explain the physical features of today's Earth taking
place over thousands or millions of years
i. Earth 4.5 billion years old
3.5 billion years first life (single celled)
C. Fossils: found on Darwin’s trip.
Shows earth is old – there is enough time for descent
with modification to occur
II. Darwin’s Finches
A. Biogeography- geographic distribution of life forms
B. Galapagos Islands- Volcanic islands off the coast of South
America
1. Species were slightly different than the ones on the mainland
C. Finches- different beaks depending on the food available
i. Cactus-eating finch:more point beak
ii. Insect-eating finch: sharp ( trees)
iii. Types of seeds
D. All descended from one mainland Finch
 DESCENT WITH MODIFICATION from a
COMMON ANCESTOR
VIDEO: https://www.youtube.com/watch?v=flDL2ZQtK8I
• The Galápagos tortoise or Galápagos giant tortoise the largest
living species of tortoise and 10th-heaviest living reptile, reaching
weights of over 400 kg (880 lb) and lengths of over 1.8 meters
(5.9 ft). Shell size and shape vary between populations- humidity,
dryness etc.
Only swimming marine iguana
Blue Footed Boobie
Blue feet and dancing to impress the female- mating ritual
Frigatebird- Do this to distract others and
take their prey
III. Natural Selection
A. Definition: mechanism for evolutionary change
B. Components:
1. Inherited variations:
 Mutations- changes in DNA
 Meiosis
2. Struggle for existence
3. Adaptations (traits that help an organism be more
suited to the environment) increase survival and
reproductive success
4. Reproduction- Genes for adaptations increase in each
generation – (Fitness- reproductive success)
Darwin’s Conclusions
a. Too many organisms are produced
b. All individuals in a species have variation
c. All individuals must struggle for
existence, and those with favorable
variation have an advantage over others
(fight for food, mate, habitat, etc.)
d. Variation that is heritable, over time
produce species.
e. Successive inheritance of favorable variation over vast
stretches of geological time produce new species.
Descent with
Modification
Survival of
the fittest
IV. Artificial Selection
Breeder choices which traits to perpetuate (dogs descended
from wolves).
Canis familiaris comes from Canis lupis domesticated 14,000
years ago.
Artificial Selection
selective breeding
of domesticated plants
and animals to produce
offspring with genetic
traits that HUMANS VALUE
The result of Natural Selection is a
population adapted to the local
environment
Evidence for Evolution
A. Fossils
B. Biogeographical
C. Anatomical
D. Biochemical
E. Embryology
F. Examples- Antibiotic
A. Fossils
8 million years ago humans chimpanzees : dozen human-like
species called hominids
The modern form of Homo sapiens first appeared about 100,000
years ago.
This species is distinguished by large brain size, mouth not
as protruding. Begin with bipedal ancestor- skulls begin
when humans began to walk on two feet
A. Fossil Record
A fossil is preserved remains or markings left
by organisms that lived in the past
Many fossils are cast in sedimentary rock
Examples:
Imprint
Mineralized
Frozen
Amber
THE FOSSIL RECORD
Dating Fossils
i. Radiometric Age
-
Measurement of
isotopes in objects
ii. Relative Age
- Age based on
layers
“Lucy”
3.2 million year old
hominid fossil
Australopithecus
afarensis
Significant because
skeleton shows
evidence of small
skull capacity like
that of apes and of
upright bipedal
posture like humans
B. Biogeography
Traits of organisms are directly linked to the
geography and environmental conditions of an area
Example:
flightless
birds, south
hemisphere
A mammal of an order (Marsupialia) whose
members are born incompletely developed and are
typically carried in a pouch
C. Anatomical Evidence
1. Homologous Structure: Structures that are similar
because they are inherited from a common ancestor
C. Anatomical Evidence
2. Analogous Structures: features are similar in function
but not in structure. They do not derive from a recent
common ancestor but in response to a similar
environment.
ANALOGOUS STRUCTURES
More Examples
Example: Insects and birds both have wings to fly,
although their wing structure is very different structure.
The fat-insulated, streamline shapes of
seals (mammals) and of penguins
(birds) is another example.
C. Anatomical Evidence
3. Vestigial structures: no longer have function. occur because
organism inherit anatomy from their ancestors.
 Examples: Some snakes have small hindlimbs
 Humans: Appendix, wisdom teeth, tail bone
THE
APPENDIX
VESTIGIAL
STRUCTURE
D. Biochemical/Molecular
1. Living organisms use DNA, and many identical enzymes (same
20 amino acids)
2. Degree of similarity of DNA sequence or amino acid structure
based on how closely related
1. Similar DNA suggests an evolutionary relationship
2. Hemoglobin
3. Cytochrome C
Our closest DNA relative is the chimpanzee, with whom we
share 98% DNA sequence similarity
E. Embryology ( Development)
1. Embryos of closely related organisms
often have similar stages in
development.
III. OTHER CONCEPTS
IN EVOLUTION
A. Antibiotic- and Pesticide-Resistance
1. Antibiotic- medicine that kills/slows the
growth of bacteria
2. Some bacteria with natural resistance will
not be killed off by the antibiotics and can
re-grow a resistant population quickly
Similar fate happens to
microbes when exposed
to cleaners and
disinfectants
When pesticides are used, some insects will
already have a natural resistance and survive the
spraying, then reproduce more insects that inherit
the resistance genes.
Eventually the same pesticides will not have the
same effect as before.
IV. Types of Evolution
A.
Divergent Evolution: consequence of adaptive
radiation- organisms sharing a common ancestor
evolve to become different according to
environmental pressures
B. Convergent evolution: arises when there are
some sort of ecological or physical driver
toward a similar solution, even though the
structure or function has arisen
independently.
Ex: sharks and dolphins share
analogous body plans, yet have
different ancestral backgrounds
(fish versus mammal)