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Evidence for Evolution 1. Evidence Evidenceof common ancestry among species comes from many sources. Evidence of common ancestry among species comes from.

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Presentation on theme: "Evidence for Evolution 1. Evidence Evidenceof common ancestry among species comes from many sources. Evidence of common ancestry among species comes from."— Presentation transcript:

1 Evidence for Evolution 1

2 Evidence Evidenceof common ancestry among species comes from many sources. Evidence of common ancestry among species comes from many sources. 2

3 #1 Fossil Evidence Fossils o Earth is Millions of years old! o Fossils in older layers are more primitive than those in the upper layers. o Extinct Fossils resemble modern animals. o This shows a common ancestry. 3

4 Types of Fossils Permineralization occurs when minerals carried by water are deposited around a hard structure 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 A natural cast forms when flowing water removes all of the original tissue, leaving an impression. 4

5 Types of Fossils Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried. Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried. Fossilized insects Fossilized insects 5

6 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 … Preserved remains form when an entire organism becomes encased in material such as ice, ash, tar … 6

7 Dating Fossils 7

8 Relative Dating of Fossils Estimates the time during which an organism lived Estimates the time during which an organism lived It compares the placement of fossils in layers of rock It compares the placement of fossils in layers of rock Scientists infer the order in which species existed Scientists infer the order in which species existed 8

9 Radiometric Dating of Fossils Measures the half-life of the isotope – the time it takes for ½ of the isotope to break down 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) Carbon-12 stable; Carbon-14 radioactive (carbon in ALL organisms) Example: 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 9

10 Radiometric Dating of Fossils Uses Radioactive Isotopes : atoms of the same element with differing neutrons Uses Radioactive Isotopes : atoms of the same element with differing neutrons Example: Example: – 12 C and 14 C – 12 C = 6 protons + 6 neutrons – 14 C = 6 protons + 8 neutrons 10

11 Radiometric Dating of Fossils 11

12 #2 Geographical Distribution Geography & environment gives evidence for evolution Geography & environment gives evidence for evolution Island species most closely resemble nearest mainland species Island species most closely resemble nearest mainland species Populations can show variation from one island to another Populations can show variation from one island to another 12

13 #3 Embryology Embryo (early developmental stage) gives evidence of evolution Embryo (early developmental stage) gives evidence of evolution Identical larvae, different adult body forms Identical larvae, different adult body forms Similar embryos, related but diverse organisms Similar embryos, related but diverse organisms Shows common ancestry Shows common ancestry Larva Adult barnacle Adult crab 13

14 #3 Embryology 14 Vertebrates all share gill slits and a tail in their early embryo stage; Share a common ancestor

15 #4 Comparative Anatomy The study of anatomy provides evidence of evolution The study of anatomy provides evidence of evolution Homologous structures are similar in structure but different in function. Homologous structures are similar in structure but different in function. Homologous structures ARE EVIDENCE of a common ancestor. Homologous structures ARE EVIDENCE of a common ancestor. 15

16 Homologous Structures ARMLEG Flipper Wing 16

17 #4 Comparative Anatomy Analogous structures are similar in function but differ in structure Analogous structures are similar in function but differ in structure Analogous structures DO NOT show common ancestry Analogous structures DO NOT show common ancestry Fly wing Bat wing 17

18 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. 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 Examples include ostrich wings, human appendix, and wisdom teeth, whale and snake pelvis/hind legs 18

19 Pythons have tiny femurs (leg bone) 19

20 #5 Molecular and Genetic Evidence AKA Biochemical Evidence AKA Biochemical Evidence Two closely-related organisms will have similar DNA, RNA, and protein (amino acid) sequences. Two closely-related organisms will have similar DNA, RNA, and protein (amino acid) sequences. This also gives evidence of a common ancestor. This also gives evidence of a common ancestor. 20

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22 Five examples of Evidence for Evolution 1.Fossils 2.Geographical Distribution 3.Embryology 4.Comparative Anatomy 5.Molecular and Genetic 22

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