Chapter 15
 Evolution: change over time
 Theory: a well-supported, testable
explanation of phenomena that have
occurred in the natural world.
 Charles Darwin , born 1809
 Was a naturalist
 1831 sailed around the world in the HMS Beagle
 On Darwin’s journeys, he drew and sketched the world
around him, and kept a journal of his observations.
 He collected insects and other small organisms.
 He collected fossils ( the preserved remains of ancient
organisms).
 He is most known for his study of the Galapagos
Islands where he made note of the different varieties of
finches, their characteristics, and their habitats.
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 Fossil record
 Hutton: geologic forces change the earth’s surface and it
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occurs over millions of years, therefore the earth is more
than 1000 years old.
Lyell: geologic features are built up/torn down over long
periods of time.
Lamarck: by selective use/disuse of organs, organisms
acquire/lose certain traits during their lifetime, traits are
passed to offspring, there fore change occurs in populations
over time.
Malthus: if the human population continues to grow
unchecked, sooner or later there would be insufficient living
space and food for everyone.
Farmers: used artificial selection to capitalize on desired
traits and incorporate them into the offspring of their
breeding stock.
 Darwin was convinced that a process like artificial
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selection was at work in nature.
He called it Natural Selection (survival of the
fittest).
Fitness is the result of adaptation.
Adaptation: an inherited characteristic that
increases an organism’s chance of survival.
Adaptations are the result of random mutations
that contribute to the organisms fitness.
Over time, natural selection results in changes in
the inherited characteristics of a population. These
changes increase a species’ fitness in its
environment.
 Darwin proposed that over long periods of time,
natural selection produces organisms that have
different structures, establish different niches, or
occupy different habitats.
 Each living species has descended, with changes,
from other species over time.
 It implies that the species are related and have
common ancestors (living and extinct)- common
descent.
 The fossil record
 Geographic distribution of living species: similar
habitats = similar selection pressures = similar
looking organisms.
 Homologous body structures: structures that have
different mature forms but develop from the
same embryonic tissues.
 Not all homologous structures are important.
Vestigial Organs: organs that are no longer used
by the body (ex: appendix, wisdom teeth).
 Similarities in embryology:
 Individuals differ and some of this variation is
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heritable.
Organisms produce more offspring than can survive ,
and many that do survive, do not reproduce.
Because more organisms are produced than can survive,
they compete for limited resources.
Each organism has unique advantages and
disadvantages in the struggle for existence. Individuals
best suited for their environment survive and reproduce
most successfully. Other individuals die or leave fewer
offspring. The process of natural selection causes
species to change over time.
Species that are alive today are descended with
modification from ancestral species that survived in the
past (common ancestors).