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Chapter 6 – Life on Earth: What Do Fossils Reveal?

Chapter 6 – Life on Earth: What Do Fossils Reveal?. Fossils are the remains or evidence of ancient organisms preserved in rock. Fossils: Surviving Records of Past Life. Preservation of ancient life is amazingly rare. Scavengers and bacteria destroy the deceased.

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Chapter 6 – Life on Earth: What Do Fossils Reveal?

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  1. Chapter 6 – Life on Earth: What Do Fossils Reveal? Fossils are the remains or evidence of ancient organisms preserved in rock.

  2. Fossils: Surviving Records of Past Life Preservation of ancient life is amazingly rare. Scavengers and bacteria destroy the deceased. Weathering and erosion of rocks containing fossils eliminates evidence. The best preserved fossils are those with “hard parts”. Even hard parts require quick burial. Soft parts are sometimes preserved.

  3. Fossil Wasp

  4. How Does Past Life Become Preserved? Most preserved evidence of ancient life is marine. Fossils are protected in rock. Where most deposition of sediment occurs. Little erosion. Some terrestrial fossils preserved: streams and lakes, tar (pits), quicksand, tree sap, ice, lava flows, or volcanic tephra (ash).

  5. Three Common Preservation Processes Rarely are the original “hard parts” preserved. Permineralization - “to spread minerals throughout. Silica, calcium carbonate, or iron dissolved in H2O percolates through sediment and is precipitated in openings. Blood vessels Nerves Bone pore space

  6. Replacement Simultaneous exchange of original substance with minerals of a different composition. Can be very precise. Fossilized wood Fossilized bone

  7. Carbonization Soft tissues are replaced by carbon as volatile components are driven off.

  8. Molds and Casts Mold - a void that the original material occupied.

  9. Casts Cast - molds that have been filled in by subsequent material. Cast Mold

  10. Soft Tissue Preservation Occasionally soft tissues may be preserved. Mostly recent organisms. Amber - Jurassic Park? Frozen in ice Preserved in “tar” (asphalt) Preserved in peat bog

  11. Amber Amber is remarkably durable. Insects No dinosaurs

  12. Frozen in Ice Pleistocene (or later) ice

  13. Frozen in Ice Pleistocene (or later) ice

  14. Preserved in Asphalt La Brea Tar Pits

  15. Preserved in Bog Lindow Man

  16. Trace Fossils Clues from trace fossils. Includes: Fossil tracks Burrows Borings Trails

  17. Fossil Trails

  18. Fossil Tracks

  19. Trace Fossil Behavior Crawling traces Grazing trace Resting traces Dwelling trace Feeding trace

  20. Trace Fossils Evidence Tracks evidence Bipedal or quadruped Digitigrade-walked on toes (cat) Plantigrade-walked on flats of feet (human) Weight Size of depression in sediment Aquatic or terrestrial Webbed feet Flesh-eating Sharp claws

  21. Fossil Abundance Why are some fossils common and others rare? Better representation for organisms with hard parts. Rapid burial Little representation from organisms living in hilly or mountainous terrain.

  22. Figuring Out How Life is Organized- Linnaeus Leads the Way Prior to Linnaeus organisms were classified in many different ways. I.e., all flying organisms Carl von Linné-Swedish naturalist Organized organisms into groups with observable traits Vertebrates, et cetera Binary nomenclature genus then species

  23. Felis Group of organisms for all cat-like organisms. Felis domesticus-common house cat Felis leo-African lion Felis fatalis-saber-toothed cat

  24. What is a Species? A species is a specific group of organisms Structural, functional, and developmental similarities Must be able to interbreed and produce fertile offspring Generally similar but not necessarily identical, i.e., exhibit variation

  25. Biologists Have the Advantage Biologists can work with many individuals and make many more comparisons than paleontologists. DNA Fertile offspring Juvenile vs. adult variation

  26. What is Taxonomy? The naming and grouping of organisms. Grouped in a hierarchy that defines levels of kinship.

  27. Domain The highest taxonomic level. Three domains Archaea Bacteria Eukarya

  28. Kingdoms A large group of related phyla. Four kingdoms Animalia-multicellular heterotrophic organisms Plantae-multicellular autotrophic eukaryotes Fungi-multicellular eukaryotes that absorb nutrients from dead organisms or are parasites Protista-mostly single cell organisms

  29. Lamarck’s Flawed Hypothesis Organisms evolve through generations due to an “inner want”. Acquired characteristics could be inherited. Giraffes. Stalin’s Lysenko Siberian wheat famine. Weak evidence that some bacteria may be able to alter their DNA.

  30. Lamarck’s Giraffes

  31. Natural Selection Charles Darwin and Alfred Wallace More organisms are born than survive to become reproductive adults. (Darwin Award) There is always variation among offspring. Competition for food, shelter, living space, and sexual partners among species having individual variations and surplus reproductive capacity consistently results in survival of the more fit and elimination of the less fit.

  32. Only a Theory? Is there evidence? Dandelion height Peppered Moth of London Lungless Salamander (Ensatina)

  33. Inheritance, Genes, and DNA Gregor Mendel and his garden peas. Genes: divide in pollen and ovules are recombine in specific ways during fertilization Chromosomes: formed of linked genes Watson, Crick, and Franklin discovered the chemical structure of chromosomes as DNA DNA: deoxyribonucleic acid

  34. DNA

  35. Species, Population, and the Gene Pool

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