Fossils_and_the_History_of_Life_

Page 1: Fossils and the History of Life

• Fossils reveal insights about the history of life on Earth.

• Focus on the adaptations of life forms over time.

Page 2: Fossils and the Fossil Record

• Footprints in sand show how temporary impressions can be made.

• Fossils: preserved remains or traces of once-living organisms.

• Types of Fossils:

  • Body Fossils: Preserved bodies or body parts.

    • Provide direct evidence of organisms.

  • Trace Fossils: Indirect evidence showing traces (footprints, burrows, feces).

    • Can indicate behavior, such as speed or parental care in dinosaurs.

Page 3: Formation of Fossils

• Fossils form in various ways.

  • Mold Fossils: created when organisms leave impressions in sediment.

  • Cast Fossils: occur when the mold is filled with a different material, retaining the original shape of the organism.

Page 4: Preservation of Body Parts

• Body parts or entire bodies can become fossils.

  • Soft parts decay quickly; hard parts (bones, teeth, shells) are more commonly preserved.

  • Minerals may seep into bones and replace original material, forming stone fossils.

Page 5: Exceptional Preservation

• Whole organisms can be preserved under rare conditions.

  • Amber: Sticky plant resin traps and preserves insects in detail.

  • Freezing: Examples include woolly mammoths found intact in ice.

Page 6: The Fossil Record

• Fossils contribute to understanding Earth's biological timeline through absolute and relative dating.

• Fossil Record: Documenting the history of life, but incomplete as many organisms do not fossilize.

  • Many dead organisms are decomposed before being fossilized.

  • Fossils require specific conditions for preservation and discovery.

Page 7: Increasing Complexity in the History of Life

• Pattern of increasing complexity in the history of life.

• Earliest Fossils: About 3.7 billion years old, representing simple single-celled organisms.

• Complex Cells: Originated around 1.8 billion years ago, larger and with specialized features including a nucleus.

• Setting the stage for multicellular life.

Page 8: Multicellular Life Forms

• Multicellular Life: Organisms with more than one cell emerged around 600 million years ago during the late Precambrian.

  • Early multicellular animals were soft-bodied without skeletons.

• Complexity increases in life forms over time, yet simple organisms remain successful.

Page 9: Patterns in Complexity

• Fossil record shows a transition from simple single-celled to complex multicellular life.

• Both simple and complex organisms coexist today.

Page 10: Increases in Diversity of Life

• Biodiversity: The variety of species on Earth.

• Adaptive Radiation: Rapid increase in biodiversity in response to favorable conditions.

Page 11: Cambrian Explosion

• Cambrian Explosion: Significant adaptive radiation around 540 million years ago after the emergence of multicellular life.

  • Major groups of animals first documented in fossils.

  • Factors contributing:

    • Habitat expansion in oceans.

    • Increased oxygen levels promoting diverse life forms.

    • Possible evolution of new features like vision.

Page 12: Decreases in Diversity of Life

• Extinction occurs when a species vanishes from the fossil record; normal in life's history.

• Mass Extinction: Sudden loss of a large number of species over a short time.

Page 13: Evidence of Mass Extinctions

• Evidence for five mass extinctions seen in the fossil record, particularly noted near the end of specific geological periods.

Page 14: The First Mass Extinction

• Occurred at the end of the Ordovician Period due to ice age conditions leading to habitat destruction.

  • Resulted in extinction of 85% of marine life.

Page 15: Permian Extinction

• The largest extinction event: About 90% of species went extinct, likely due to volcanic eruptions in Siberia.

  • Relate to global warming and oceanic disruptions.

Page 16: Cretaceous Mass Extinction

• Associated with the extinction of dinosaurs, linked to a meteorite impact.

  • Evidence includes a large crater in the Yucatán Peninsula.

  • The impact disrupted the food chain and caused ecological changes.

  • Paved the way for mammalian and avian diversification.

Page 17: Changes in Life Forms - Birds

• Archaeopteryx: The first known bird, living about 150 million years ago, links birds to dinosaurs.

  • Characteristics: wings, feathers, wishbone, but also has teeth and claws indicative of its ancient lineage.

Page 18: Features of Archaeopteryx

• Anatomical features connect Archaeopteryx to dinosaurs.

• Its body reflects evolutionary transition between reptiles and birds.

Page 19: Evolutionary Changes in Birds

• Archaeopteryx is crucial for understanding the evolution of birds from dinosaurs.

  • Changes over time: development of feathers, loss of claws, and modifications in tail structure.

Page 20: Changes in Life Forms - Whales

• Fossil evidence shows that whales evolved from land mammals.

  • They adapted to aquatic life and breathe using lungs.

Page 21: Whale Evolution

• Pakicetus: The oldest known whale relative, exhibiting mammalian characteristics.

  • Transitioned to aquatic adaptations seen in later fossil species like Ambulocetus and Basilosaurus, demonstrating the gradual shift from land to marine adaptations.