chapter 15 – theory of evolution 15-2: evidence of evolution
TRANSCRIPT
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Chapter 15 – Theory of Evolution
15-2: Evidence of Evolution
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The Fossil Record Fossil evidence shows a long history of
Earth – constant change + diversityShows forms of organisms
appeared, lasted for long periods of time, and then disappeared, only to be followed by newer forms of life that also eventually disappeared
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Nature of Fossils FossilFossil
Trace of a long, dead organism Found in sedimentary rock layers Examples:
Shells Bones Teeth Woody stems (plants) Whole organisms Molds Casts
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The Age of Fossils In, 1669, Steno proposed the
PRINCIPLE OF PRINCIPLE OF SUPERPOSITIONSUPERPOSITION Stated that successive layers of
rock or soil deposited on top of one another by wind and water
Layers known as strata The lowest layer was the oldest;
the top layer was the youngest Fossils found in same layer, are
the same age
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Geologic Time Scale
Timeline of when organisms existed Based on fossil
evidence
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The Age of Fossils Relative ageRelative age
States that a fossil is younger or older than another fossil
Absolute ageAbsolute age Its actual age in
years Can be determined
by radiometric dating
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Distribution of Fossils Fossil Record inferences:
Different organisms lived at different times Today’s organisms are different from those in
the past Fossils found in adjacent layers are more like
each other than fossils found in deeper or higher layers
Lived during same time periods
Can compare when and where different organisms existed
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Transitional species The fossil records describes a gradual
sequence of forms over time Transitional species have intermediate
features between ancestors + older descendants Example:
Whales
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Distribution of Fossils(cont.)
BiogeographyBiogeography Study of the locations of organisms around the
world It compares recently formed fossils with types
of organisms living in the same geographical area
Shows that new organisms arise in the areas where similar forms already lived
Examples: Armadillos Kangaroos
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Distribution of Fossils(cont.)
North + South America
Australia
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Anatomy & Embryology Anatomy
The study of the body structure of organisms
Homologous Structures
Structures that originated by heredity from a common ancester
Ex. - Forelimbs
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Anatomy & Embryology Analogous
Structures Features that
have similar functions but do not derive from same ancestral structures
Ex – Wings or Beaks
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Anatomy & Embryology Vestigial structures
Structure that seems to serve no function but resembles structures with functional roles in related organisms
Examples: Tailbone Pelvic bone in
whales/snake Appendix Wisdom teeth
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Anatomy & Embryology Embryology
Study of how organisms develop Example:
Vertebrates
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Biological Molecules Organisms that share many traits should have a
more recent common ancestor than organisms that share fewer traits
By looking at DNA, RNA, or Amino Acid sequences, scientists can infer common ancestry
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Developing Theory Mid-1900s
Integrated theory of natural selection with genetics
Called the Modern Synthesis of Evolutionary Theory
Widely accepted + applied by scientists Phylogeny
Relationships by ancestry among groups of organisms
Scientists create a phylogenetic “tree” to show relationship/ancestry
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