15.3 Darwin’s Case Notes
 Nevada State Science Content Standard: L.12.D.1 Students know organisms can
be classified based on evolutionary relationships. E/S
 Objective:
Students will state Darwin’s theory of evolution by natural selection.
 Key Vocabulary
Artificial selection –
Struggle for existence –
Adaptation –
Survival of the fittest –
Natural selection –
Descent with modification –
Common descent –
Homologous structure –
Vestigial organ –
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*When Darwin returned from the voyage of the Beagle, he wrote about his ideas
but waited many years to publish them.
*Darwin was prompted to publish his theory of evolution by an essay by Wallace
on evolution.
Were Darwin’s hypotheses about natural selection and evolution similar to the
ideas of most other scientists of his time? Explain. No; Darwin’s hypotheses
challenged the fundamental scientific ideas of the times.
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Artificial selection – selection by humans for breeding of useful traits from the
natural variation among different organisms
*In 1859, Darwin published his revolutionary scientific ideas in a work entitled
On the Origin of Species.
*When a farmer breeds only his or her best livestock, the process involved is
artificial selection.
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Struggle for existence – competition among members of a species for food, living
space, and other necessities of life
Adaptation – inherited characteristic that increases an organism’s chance of
survival
*When lions prey on a heard of antelope, some antelope are killed and some
escape. Which part of Darwin’s concept of natural selection might be used to
describe this situation? Survival of the fittest
*According to Darwin’s theory of natural selection, the individuals that tend to
survive are those that have variations best suited to the environment.
*Darwin’s theory of evolution is based on the idea of natural variation and
natural selection.
*An adaptation is an inherited characteristic that can be physical or behavioral.
*Darwin called the ability of an organism to survive and reproduce in its
environment fitness.
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Survival of the fittest – process by which individuals that are better suited to
their environment survive and reproduce most successfully; also called natural
selection
Natural selection – process by which individuals that are better suited to their
environment survive and reproduce most successfully; also called survival of the
fittest
Descent with modification – principle that each living species has descended,
with changes, from other species over time
*Darwin’s theory of evolution suggests that species change over time.
*Darwin proposed that natural selection takes place as individuals best suited to
the environment survive and reproduce.
*According to Darwin’s theory of evolution, species change over time.
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Common descent – principle that all living things were derived from common
ancestors
*Darwin viewed the fossil record as a record of evolution.
*People of Darwin’s time understood that fossils were preserved remains of
ancient organisms.
According to Darwin’s theory of evolution, all species on Earth are united by
common descent.
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*Darwin concluded that in similar environments around the world, natural
selection could produce similar structures in unrelated species.
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Homologous structure – structures that have different mature forms in different
organisms but develop from the same embryonic tissues
Vestigial organ – organs that serve no useful function in an organism
*The number and location of bones of many fossil vertebrates are similar to
those in living vertebrates. Most biologists would probably explain this fact on
the basis of a common ancestor.
*In humans, the pelvis and the femur, or thighbone, are involved in walking. In
whales, the pelvis and femur would be called vestigial structures.
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*According to Darwin’s theory of evolution, organisms produce more offspring
than can survive.
The hypothesis that species change over time by natural selection was proposed
by Darwin.