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.