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INTRODUCTION TO EVOLUTION
Honors Biology
INTRODUCTION TO EVOLTUION
• Brainstorm – What is Evolution?
OVERVIEW OF EVOLUTION
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Evolution is a change in species over time
Many misconceptions
Evolution is a theory
Not one or another
Overlying theme in Biology
Earth is old!
HOW DO WE KNOW EVOLUTION
EXISTS?
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Fossils
Homologous Structure
Vestigial Structures
Embryology
Similarities in
Macromolecules
FOSSILS
• Fossil evidence shows a long history of life on
Earth
• Organisms live, last for awhile and
disappeared; new forms live, last and
disappear
FOSSILS
• A trace of a long dead organism
• Many found in sedimentary rock
– Sediment deposited by wind or water
– Develop from hard elements of body
– Minerals replace tissue  fossil
FOSSIL
• Mold:
– Imprint in rock that is shape of organism
– Cast is a mold filled with hard material
• Many different types of fossils
– Tracks of animals
– Mosquito trapped in
amber
FOSSILS
• Distribution of fossils
– Law of superposition:
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Layers of strata
Lower levels are older; upper levels are newer
Relative age of higher up is younger
Can also figure absolute age
– http://www.pbs.org/wgbh/evolution/library/04/3
/quicktime/l_043_01.html
FOSSILS
• Distribution of fossils
– Succession of Forms
• Fossils live and then become extinct
• Mass extinctions
FOSSILS
• Biogeography
– Study of geographical distribution of fossils and
living organisms
– Fossils in same area as ancestors
– Giant fossil kangaroos are found in ________?
HOMOLOGOUS AND ANALOGOUS
STRUCTURES
• Homologous Structures:
– Similar features
– Common ancestor
– Forelimbs of vertebrates
– Thumbs in primates
• Analogous Structures:
– Similar features
– No common ancestor
– Dolphins and shark
VESTIGIAL STRUCTURES
• Structures that were once needed and not
needed anymore
• Conserved
• Examples
– Human appendix
– Hind limbs in whales
– Human tail bone
EMBRYOLOGY
• Similarities in vertebrate embryos
• Ontogeny recapitulates phylogeny
• Human embryos have:
– Tails
– Webbed fingers and toes
– Gill slits
SIMILARITIES IN MACROMOLECULES
• Compare DNA, RNA, Amino Acids
• More recent common ancestor; more in
common
• Hemoglobin of humans and gorillas differ by 1
amino acid; humans and frogs by 67 amino
acids
• DNA of chimps and humans 99% similar (more
similar than chimps and gorillas)
WHAT DO I KNOW?
• What is evolution?
• What are 5 ways we know that evolution
exists?
• Be able to explain/give examples for each
form of evolution.
• What is the difference between a homologous
and an analogous trait