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CHAPTER 22
DESCENT WITH MODIFICATION:
A DARWINIAN VIEW OF LIFE
• On November 24, 1859, Charles Darwin published
On the Origin of Species by Means of Natural
Selection.
• Two major points:
• Today’s organisms descended from ancestral species.
• ___________________ provided a mechanism for
evolutionary change in populations.
Came to the conclusion that the Earth
was _______ and constantly _______.
• Darwin’s views were influenced by
1. Fossils in sedimentary rocks.
Fig. 22.2
2. A 5-year voyage around the world
Fig. 22.4
3. ________________ theory of ____________________ –
earth processes are constant over time
4.Jean Baptiste _________- 1809 publication of a theory of
evolution based on his observations of fossil chronologies
in the Natural History Museum of Paris.
The Origin of Species challenged a worldview that
had been accepted for centuries
• The Old Testament account suggests rapid
creation, not evolution
• The Darwinian view of life has two main features.
(1) The diverse forms of life have arisen by descent
with modification from ancestral species.
(2) The mechanism of modification has been natural
selection working over enormous tracts of time.
• This evolutionary tree of the elephant family is
based on evidence from fossils.
Fig. 22.7
Natural selection in easily observed
• _________________________ in insects
• _________________ resistance in humans
• 3TC-resistant strains of HIV become 100% of the
population in just a few weeks.
•In each generation the percentage of
resistant individuals increases.
•_________________ favors those characteristics in
a variable population that fit the current, local
environment.
Natural selection does not prove large-scale evolution and
speciation, only adaptation
Evolution is inferred
What is the evidence for evolution?
1. Homologous ___________________
For example, the forelimbs of human, cats, whales,
and bats share the same skeletal elements, but
different functions
Fig. 22.14
2. _________________ in some creatures
• Example-some snake skeletons have vestiges of the
pelvis and leg bones
• Fossil whales with vestigal legs and pelvis
3. ______________________
All vertebrates “look” the same as early embryos, then changes
are observed later.
4. All of life shares the same ________________
5. DNA sequences are more homologous in “like”
creatures than ________ ones
6. The _________________
Different organisms appear at distinct times in the fossil
record
…..But transition creatures are almost non-existent
7. Isolated places have distinct populations
• There are numerous unique creatures on isolated islandsAustralia, Galapagos islands,….
• Old World vs New World monkeys
How does one reconcile evolution with Genesis account?
Many scholars reject evolution theory outright.
Others suggest vast periods of time between 1st and 2nd days of
Genesis creation- .
Others suggest God-directed evolution – Theistic evolution
Michael Behe- suggests that life cannot “just happen”, but is
“irreducibly complex”
• Uri Miller experiment- Mix NH4, methane, water
in intense heat and electrical current
• Observe simple macromolecules are formed
• Is this evidence for a pre-biotic soup forming resulting
in an organism?
History suggests that our descendents will look
back at this generation and say “they
understood so little”