Download Chapter 10-Evolution and Natural Selection

Chapter 10-Evolution
and Natural Selection
10-1 Charles Darwin
10-2 The Evidence for Evolution
10-3 Natural Selection
10-1 Charles Darwin
At age 22 Charles Darwin sailed on the
HMS Beagle from England to make a
survey of the coast of South America.
 He spent 5 years at sea making
observations and taking careful notes.
 Darwin’s famous book, The Origin of
Species, caused great controversy
because of his conclusions that species
change over time. His implication that
apes were close relatives of humans
caused great alarm.

Darwin proposed that natural selection was
the mechanism for species change.
 Organisms with traits well suited to an
environment are more likely to survive
and produce more offspring than
organisms without these favorable traits.
 The modern theory of evolution is a
combination of Mendel’s ideas about
genetics and Darwin’s ideas about natural
selection.
10-2 Evidence for Evolution

The fossil record
◦ Fossils are traces of dead organisms. They can
be tracks or footprints, insects trapped in sticky
tree sap, impressions of leaves or skin, or
animals buried in tar.
◦ Fossils are produced by the rapid burial in mud
or sediment. Bone and shell is replaced by
hard minerals in the sediment. Soft tissues do
not fossilize unless there is no oxygen to
prevent decay.
◦ The fossil age is determined by using
radioactive dating. This process uses the
radioactive element in the rock to determine
how much the element has decayed over time.
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
Comparing organisms
◦ Homologous structures are structures that
share a common ancestry.
◦ Vestigial structures are structures that
apparently have no purpose. They are
believed to be a left over piece of an
evolutionary past.
◦ Developmental patterns are believed to show
evolutionary relationships
10-3 Natural Selection

Darwin believed that the principle
mechanism of development was natural
selection.
◦ The key factor in natural selection is the
environment.
◦ The environment presents challenges that
individuals with particular traits can better
overcome.
◦ Traits possessed by organisms successful at
survival and reproduction are more likely to be
transmitted to the next generation.
◦ These traits become more common over time.
The Peppered Moth – In 1850 the dark
peppered moth was rare in England. Over
time the dark colored moth became more
common due to the sooty coating on the
bark.
 Sickle Cell Anemia – Homozygous sickle
cell alleles cause death in an individual.
Heterozygous sickle cell alleles protect an
individual from malaria.
 Seaside Sparrow 