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EVOLUTION
the CHANGE in populations over time.
CHARLES DARWIN
– English biologist
who proposed the
theory of
evolution
– Wrote The Origin
of Species in
1859 (20 years
after voyage);
very controversial
Darwin on HMS Beagle
(a 5 year voyage)
Darwin explains natural
selection:
1. VARIATION exists among members
of a population
Recall lab: the species of finch that varied in their beak shape!
Fish, for example,
may differ in
color, size, and
speed.
What causes variation?
• Mutations (initially)
• Sexual reproduction makes
different combinations of
traits possible
Adaptations:
• A variation that helps an organism to survive
2. Those with adaptations survive
and reproduce AND pass on the
adaptation to the offspring
• Ex. Speedy fish survive
Recall lab: the spoon and fork varieties were more successful than the knife ones
At getting pasta food. The survive and offspring inherit this successful variation.
3. Over time, successful variations
make up most/all of the population
•The population may
look quite different
from their ancestors
Recall lab: After five generations, the knife variation was almost nonexistant,
Whereas the fork and spoon numbers climbed.
Evidence For Evolution:
1. Direct Evidence for evolution:
(we can see it happening in a short
period of time).
In bacteria, antibiotic resistance
How it happens: (p. 399)
Non-resistant
bacterium
Antibiotic
Resistant
bacterium
The bacteria in a
population vary in
their ability to resist
antibiotics.
When the population is
exposed to an antibiotic,
only the resistant
bacteria survive.—
natural selection!
The resistant bacteria
live and produce more
resistant bacteria.
• Today, penicillin no longer kills as many
species of bacteria because some species
have “evolved” into penicillin-resistant
populations.
2. Indirect Evidence
for Evolution:
(we can’t see it happening in a
short period of time)
a. Fossils
• they provide a record of early life and how it is
different from species today
• The fossil record is incomplete (most things
decompose rapidly and do not fossilize)!)
Camel Evolution
Age
Organism
Skull and
teeth
Limb
bones
Paleocene
65 million
years ago
Eocene
54 million
years ago
Oligocene
33 million
years ago
Miocene
23 million
years ago
Present
b. Anatomy
• Structural features with a common evolutionary
origin are called homologous structures.
• Homologous
structures can be
similar in
arrangement, in
function, or in both.
Crocodile
forelimb
Whale
forelimb
Bird
wing
Anatomy (cont.)
•Analagous structures: no common
ancestor, but have common function
• For example, insect and bird wings probably evolved
separately when their different ancestors adapted
independently to similar ways of life.
Anatomy (cont.)
• Many organisms have vestigial structuresstructures that no longer have a function.
• they show structural change over time.
• Vestigial structures,
such as pelvic bones
in the baleen whale,
c. Embryology
• the shared features in the young embryos that
suggest evolution from a distant, common
ancestor.
Pharyngeal
pouches
Fish
Reptile
Pharyngeal
pouches
Bird
Mammal
• The embryos of a fish, a reptile, a bird, and a mammal have a tail
and pharyngeal pouches.
d. Biochemistry
If the makeup of certain molecules is more
similar, that would suggest a closer evolutionary relationship.
Percent Substitutions
of Amino Acids in
Cytochrome c Residues
Comparison of Organisms
Biochemical Similarities of Organisms
Two orders of mammals
5 and 10
Birds vs. mammals
8-12
Amphibians vs. birds
Fish vs. land vertebrates
14-18
18-22
Insects vs. vertebrates
27-34
Algae vs. animals
57
Convergent Evolution = different
species evolve in similar ways
Divergent Evolution: same ancestral
species evolve different adaptations over
time due to different environments
Some Structural Adaptations:
Mimicry:
One species resembles another species
The viceroy (Limenitis sp.; right) and monarch (Danaus sp.) butterflies look
very similar but may differ in their taste to avian predators.
Camouflage= kind of mimicry in which a
species blends in with its surroundings
• NPR Too Big to Publish
http://www.npr.org/templates/story/story.php?storyId=100542500&ps=rs
NPR interview
• http://www.youtube.com/watch?v=XV8h6J
H8zVw&safety_mode=true&persist_safety
_mode=1&safe=active
• http://www.youtube.com/watch?v=PvAi8m
7EUgc&safety_mode=true&persist_safety
_mode=1&safe=active
Darwin’s finches
• http://www.youtube.com/watch?v=l25MBq
8T77w&safety_mode=true&persist_safety
_mode=1&safe=active