Evidence for Evolution
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Transcript of Evidence for Evolution
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Evidence for Evolution
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EvidenceEvidence of
common ancestry among
species comes from many sources.
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#1 Fossil Evidence FossilsoEarth is Millions of
years old!oFossils in older layers
are more primitive than those in the upper layers.
oExtinct Fossils resemble modern animals.
oThis shows a common ancestry.
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Types of Fossils Permineralization
occurs when minerals carried by water are deposited around a hard structure
A natural cast forms when flowing water removes all of the original tissue, leaving an impression.
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Types of FossilsAmber-preserved fossils are
organisms that become trapped in tree resin that hardens after the tree is buried.
Fossilized insects
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Types of Fossils Impressions are imprints left in
rock Preserved remains form when
an entire organism becomes encased in material such as ice, ash, tar …
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Dating Fossils
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Relative Dating of Fossils
Estimates the time during which an organism lived
It compares the placementof fossils in layers of rock
Scientists infer the order in which species existed
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Radiometric Dating of Fossils
Measures the half-life of the isotope – the time it takes for ½ of the isotope to break down
Carbon-12 stable; Carbon-14 radioactive (carbon in ALL organisms)
Example:– Carbon-14 has a half-life of 5730
years; decays into Carbon-12– Compare ratio of C-14 to C-12 to age
fossil
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Radiometric Dating of Fossils
Uses Radioactive Isotopes: atoms of the same element with differing neutrons
Example:– 12C and 14C– 12C = 6 protons + 6 neutrons– 14C = 6 protons + 8 neutrons
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Radiometric Dating of Fossils
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#2 Geographical Distribution
Geography & environment gives evidence for evolution
Island species most closely resemble nearest mainland species
Populations can show variation from one island to another
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#3 Embryology Embryo (early developmental stage)
gives evidence of evolution Identical larvae, different adult body
forms Similar embryos, related but diverse
organisms Shows
commonancestry
Larva
Adult barnacleAdult crab
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#3 EmbryologyVertebrates all share gill slits
and a tail in their early
embryo stage;
Share a common ancestor
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#4 Comparative Anatomy
The study of anatomy provides evidence of evolution
Homologous structures are similar in structure but different in function.
Homologous structures ARE EVIDENCE of a common ancestor.
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Homologous StructuresARM LEG Flipper Wing
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#4 Comparative Anatomy
Analogous structures are similar in function but differ in structure
Analogous structures DO NOT show common ancestry
Fly wing
Bat wing
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Structural patterns are clues to the history of a
species. Vestigial structures are
remnants of organs or structures that had a function in an early ancestor.
Examples include ostrich wings, human appendix, and wisdom teeth, whale and snake pelvis/hind legs
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Pythons have tiny femurs (leg
bone)
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#5 Molecular and Genetic Evidence
AKA Biochemical Evidence
Two closely-related organisms will have similar DNA, RNA, and protein (amino acid) sequences.
This also gives evidence of a common ancestor.
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Five examples of Evidence for Evolution
1.Fossils2.Geographical
Distribution3.Embryology4.Comparative Anatomy5.Molecular and Genetic
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