Natural Selection and Evidence for Evolution

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Transcript Natural Selection and Evidence for Evolution

Do Now
• Explain why the following statement is false:
• A giraffe living in the savanna is having
difficulty reaching the leaves on trees. His
neck is too short to reach them. The giraffe
stretches his neck everyday and eventually
his neck is long enough to reach the leaves.
The giraffe later has offspring who have
inherited this long neck too.
Darwin Presents His Case
Darwin Island
I. On the Origin of Species
A. Darwin wrote a book based on all of his
B. His conclusion was eventually called
evolution by natural selection
C. His findings directly disputed everything
he believed about the origin of life.
D. Was afraid to publish the book
II. Alfred Wallace
A. 25 years after Darwin returned from the
Galapagos, Wallace sends him an essay.
B. The essay was about evolution.
C. Darwin published his book immediately.
D. Darwin and Wallace present their info to
other scientists and it became
III. Artificial Selection/Selective
A. Darwin knew nothing about genetics
B. He noticed that plants and animals had
differences or advantages over each other
C. Farmers chose the better organisms to
breed another generation
IV. Natural Selection
A. Also known as Survival of the Fittest
B. Darwin and Malthus saw competition for
survival (struggle for existence).
C. Organisms that were well suited to their
environment were fit due to adaptations
they inherited. (examples p. 461)
D. The better suited (fit) animals survived,
less fit died out changing the population
over time.
E. Misconception:
Organisms that just so happen to have a trait that
benefits them are the ones “selected”.
V. Descent with Modification
A. Used to explain why
each species looks
different today than
their ancestors
B. Each living species
has descended, with
changes, from other
species over time.
C. Implies that all
organisms are related
(common descent)
VI. Evidence of Evolution
A. Fossil Record
1. remains of ancient life
2. imprints, amber, ice, rock, tar
B. Homologous
1. anatomical
similarities among
organisms but have a
different function
Analogous Structures
• Similar function,
but different origin
– Ex: Insect wing vs.
Bat wing
• Both important in
flight, but only one
has bones!
C. Vestigial Structures
1. organs that have no useful function and
have often shrunk in size to a trace
D. Embryology
1. embryonic stages of many organisms
are similar
E. Biochemistry
1. similarities in body chemicals
between species
Amino acid similarities
Evolution: Library: Whale Evolution