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Evidence of Evolution

Evidence of Evolution. Evidence of Evolution. EVOLUTION - genetic change in a population of organisms over time 4 Types of Evidence that scientists have gathered in support of evolution Fossils Comparative Anatomy & Structures Embryology Biochemistry (Proteins & DNA). Fossils.

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Evidence of Evolution

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  1. Evidence of Evolution

  2. Evidence of Evolution • EVOLUTION - genetic change in a population of organisms over time • 4 Types of Evidence that scientists have gathered in support of evolution • Fossils • Comparative Anatomy & Structures • Embryology • Biochemistry (Proteins & DNA)

  3. Fossils • What is a FOSSIL? • The preserved remains or traces of an organism that is no longer living • Usually found in sedimentary rocks

  4. What can fossils show? • Organisms have appeared and disappeared, and have changed over time • Extinction of species • Transitional forms reveal links between groups: Archaeopteryx: between reptiles & birdsEustheopteron: amphibious fish Seymouria: reptile-like amphibian Also, mammal-like reptiles & whales with hind limbs • Reveals ancient climate & environmental conditions • Indicates development of life from simple to complex • Indicates life began in water

  5. Fossils • Types of Fossils: • 1. IMPRINT – thin, soft object (leaf, feather) is buried and sediments later harden • 2. MOLD – Buried organism disappears and leaves an empty space • 3. CAST – mold filled by minerals (replica of organism) • 4. PETRIFICATION – minerals replace hard parts (bones, teeth, etc.) of organism • 5. AMBER – entire organism fossilized in tree sap • 6. FROZEN – entire organism frozen in ice • 7. TRACE – footprints, trails, etc.

  6. How can fossil age be determined? • Depth of fossils help to determine their age • Lower layers are older than those in upper layers • Radioactive Isotope Dating • Carbon-14, Uranium-238, Potassium-40 • Measure the proportion of an isotope relative to its more stable form (half life)

  7. Why is the fossil record incomplete? • 1. Soft tissue rarely preserved • 2. Movement of the earth’s crust has obliterated or covered many fossils • 3. Fossilization takes place only in certain types of habitats and under favorable conditions • 4. Paleontologists have not dug up every place on earth

  8. Comparative Anatomy • Study of anatomical structures to find similarities and differences • HOMOLOGOUS STRUCTURES – parts with similar basic structure (derived from same structures in embryo—same common descent), but may vary in function

  9. Comparative Anatomy • ANALOGOUS STRUCTURES – structures that have the same function (may look somewhat alike), but have different structures and DO NOT have a common descent • Example: wings have developed independently in insects, reptiles, birds, and bats

  10. Comparative Anatomy • VESTIGAL STRUCTURES – reduced body parts (in comparison to the same complex structure in other organisms) that have little to no function; remnant of an ancestor • Examples: • Human appendix (other mammals it is necessary to aid in digestion) • Human external ear muscle (useless, but still there) • Human tailbone (coccyx) • Human wisdom teeth • Bird wings – Penguins adapted for swimming, ostrich wings for balance and courtship

  11. Embryology • Patterns of embryological development can indicate a common ancestry • Fish, birds, mammals & reptiles all have gills; only fish retain theirs • Fish, birds, humans & reptiles all have tails; ALL but humans retain theirs

  12. Biochemical Similarities • Similarity of proteins, RNA & DNA molecules • The more closely related organisms are, the more similar is the biochemical makeup • Indicates common ancestor • Universality of genetic code – supports evolution • Similar chemistry & structure of chromosomes among Eukaryotes • Chlorophyll is the same basic molecule in all photosynthetic organisms

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