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Evolution: Evidence and
Theory
Evolution: an orderly succession
of changes
Theories of Evolution
• Jean Baptiste de Lamark - living species
descended from similar extinct species and
acquired traits were passed on
• Acquired trait - from experiences, not
genes
• Water birds - webbed feet came from
stretching toes
Lamarck’s Theory at work
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Charles Darwin
• Species are modified
by natural selection
• Natural selection organisms with
favorable traits
reproduce more
successfully
• Population - # of
organisms with
favorable traits
increase
Darwin
• Naturalist on the H.M.S.
Beagle (1831-1836) - mapped
and collected specimen in
South America and South
Pacific
• The Origin of Species(1859) Darwin’s book on Natural
Selection
Darwin’s Theories
• Descent with
modification - new
species are modified
descendants of older
species
• Modification with
Natural Selection organisms with more
favorable traits leave
more offspring
Darwin Vocabulary
• Adapt - changes made
by an organism
• Adaptive Change - a
favorable trait for the
environment
http://www.pbs.org/wgbh/evolution/about/overview_series.html
Evidence of Evolution
• Fossils – a trace of a long-dead organism
• mold – imprint of organism on a rock
• cast – imprint filled with minerals, rocklike
Law of Superposition
– layers of rock were
deposited on one another
• Stratum – layer of earth
• Relative Age – determines old, young by
examining layers
• Absolute Age – estimated from sediment on top
Succession of Forms
• Extinct – species disappeared
• Mass Extinction – large number
of species disappeared
Homologous Structures
• Similar features
from a shared
ancestor
Vestigial Structures
• Structures no longer useful in
modern organisms
Similarities in Embryos
• Early stages of
vertebrate embryos
are very similar
Similarities in Biochemistry
• The more similar the amino acid sequence,
the more common the ancestor