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NATURAL SELECTION
How do we organize the
diversity of life?
How do we explain:
• great diversity of organisms?
•organisms that are well-adapted to their
environment?
•similarities and relationships of organisms
(all use same basic genetic information)?
Jean-Baptiste Lamarck (1744-1829)
Theory of Use and Disuse – Genetic traits can
be developed.
Example – Blacksmith and bigger biceps
Example – Giraffe and longer neck
Inheritance of Acquired Characteristics – Traits developed during your
life can be given to offspring.
Problem – How do you account for any variety in giraffes?
What about those who don’t have long necks?
Did trees all of a sudden get taller?
What if someone gets a tattoo?
Dyes their hair?
Loses a finger?
Inheritance of Acquired Characteristics – WRONG! Traits developed during
your lifetime cannot be passed on. You cannot will yourself to have new traits.
Charles Darwin (1809-1882)
Voyage of the H.M.S. Beagle –
(1831-1836)
Among other observations, saw
finches on the Galapagos
Islands off the coast of South
America. These finches had
been seen nowhere else in the
world, but resembled those on
South American coast. How did
they become so well-suited to
their environment?
Darwin Video –
http://www.teachersdomain.org/resources/tdc02/sci/life/evo/lp_darwin/index.html
Theory of Natural Selection
1. Genetic Variation – Each organism
has unique DNA sequence and traits.
2. Overproduction of offspring – More kids are
produced than can survive.
3. Struggle for existence – Kids compete for
limited resources (food, shelter, mates).
4. Differential survival and reproduction – Those that live, reproduce
and pass on traits.
# of rabbits
Example #1 – Speedy Rabbits
What will this graph look like if a predator is
introduced into the rabbit’s habitat?
PBS video - natural selection (6:41)
Slow
Fast
Example #2 – Peppered moth. Two different colors – light and dark. How
many moths do you see in each picture?
After 1850 most had
dark-colored wings.
Prior to 1850 most had
light-colored wings
WHY?
DOES EVOLUTION HAPPEN WITHIN ONE GENERATION?
EXAMPLE: A LIGHT-COLORED MOTH IS MOVED TO AN
AREA WITH SOOT COVERED TREES. CAN THIS
INDIVIDUAL MOTH EVOLVE?
Evidence to support Theory of
Evolution and Natural Selection
1. Comparative Anatomy – Bones have similar patterns
Fossil
Video
(7:00)
2. Molecular Biology – all organisms use same A, T, C, G, but
different order. Sequence can acquire mutations which can
be passed on to next generation. Mutations can result in different traits.
Video – includes UWMadison researcher,
Dr. Sean Carroll
(7:00)
3. Selective breeding – Humans have been performing
natural selection experiments for centuries using “artificial selection”.
TEOSINTE AND CORN
Artificial Selection of Wild Mustard
Video Clips
Classification of Species (2:09)
Natural Selection - Darwin (6:49)
PBS - Adaptation - Hummingbirds (6:39)
PBS - Adaptation - Mantis camouflage (:58)
PBS - Molecular Evidence (4:47)
PBS – Salamander Migration (3:21)
Using What You Have Learned
How would Darwin
use his Theory of
Natural Selection to
explain the insect
seen in this video?