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Exciting Evolution
Chapter 22
I. Science as a Process
A. Linnaeus (1707-1778) – specialized in
Taxonomy – naming and classifying
organisms. Grouped similar species into
categories showing relationships
Developed binomial (two part) naming according
to genus and species (i.e. Homo sapiens)
Science as a Process
B. Early Theories of Change
To Explain the fossil record
Catastrophism – each boundary between
strata corresponded in time to a catastrophe
(flood/drought etc) that destroyed many
species living at the time. Other species moved
to these areas from surrounding areas.
Early Theories of Change
To Explain the fossil record
 Gradualism – profound change is the
cumulative product of slow but continual
processes (canyons formed by rivers cutting
through rocks
Science as a Process
Uniformitarianism – geologic processes have
not changed throughout Earth’s history (ex.
forces that build mtns and erode mtns are the
same now as in the past)
C. First Evolution Hypothesis
Jean Baptiste Lamarck –published his theory of
evolution in 1809
1. Use and Disuse – those parts of the body used
extensively to cope with the environment becomes
larger and stronger while those not used deteriorate
2. Inheritance of Acquired Characteristics –
modifications an organism acquires during its
lifetime can be passed along to its offspring.
II. Darwin’s Descent with
A. Conclusions
1. Earth must be old (6000 + years)
2. Slow and subtle processes over long periods of
time can add up to substantial change
Darwin (cont)
 Unity of life – all organisms are related
through descent from some unknown ancestor
that lived in the remote past. As the
descendents moved into various habitats over
millions of years, they accumulated diverse
adaptations that helped them survive in their
Darwin’s Observations
1. Members of a population often vary greatly
in their traits
2. Traits are inherited from parents to offspring
3. All species are capable of producing more
offspring than their environment can support
4. Due to lack of food or other resources, many
offspring do not survive
Inference 1
Individuals whose inherited traits give them a
higher probability of surviving and
reproducing in a given environment tend to
leave more offspring than other individuals
Inference 2
This unequal ability of individuals to survive
and reproduce will lead to the accumulation of
favorable traits in the population over
Natural Selection
A process where individuals that have certain
heritable characteristics survive and reproduce
at a higher rate than other individuals.
Over time, natural selection can increase the
match between organisms and their
If an environment changes, or if individuals
move to a new environment, natural selection
may result in adaptation to these conditions
Change in the genetic composition of the
population over time
Individuals cannot evolve, only a population of
interbreeding individuals
Only heritable traits can be amplified by
natural selection (not traits acquired in lifetime
– like big muscles)
Examples of natural selection
Galapagos finches – beaks different depending
on food source
Antibiotic resistance of bacteria
Insecticide resistance in insects
Drug Resistant HIV (due to differences in
reverse transcriptase enzymes)
III. Other Evidences of Evolution
A. Homology – similarities in characteristics
resulting from common ancestry
1. Anatomical Homologies – similar structures in
organisms with similar ancestry (bones in human
arm, cat paw, whale flipper, bat wing)
*vestigial organs- structures of little or no
importance to an organism (like our
appendix) – may have had a job in
A. Homology
2. Embryological Homologies- similarities in
embryonic development
ex. all vertebrate embryos have pharyngeal pouches
3. Molecular Homologies – certain
characteristics are shared by all organisms at
the molecular level
DNA and RNA – universal genetic code
Many similar proteins
B. Biogeography
geographic distribution of species
Species tend to be more closely related to
other species from the same area than to other
species with the same way of life but living in
different areas
Islands are a perfect example of
biogeographical evidence of evolution
ex. finches in Galapagos, honeycreepers and fruit
flies in Hawaii
C. Fossil Record
Prokaryotes are thought to be the earliest
organisms, and the oldest known fossils are
Vertebrates appear in the fossil record as they
are believed to have evolved
Fish – amphibians – reptiles – mammals and
Convergent Evolution
Independent evolution of similar features in
different lineages
Develop similar characteristics due to living in
similar environments
ex. Sugar glider (marsupial) and flying squirrel
(placental mammal)