Integrated Science Ch. 14 The History of Life

I.Fossil Evidence of Change - The fossil record shows that past organisms were very different from those alive today and have been affected by several mass extinctions.

I.Fossil Evidence of Change - The fossil record shows that past organisms were very different from those alive today and have been affected by several mass extinctions. Mass Extinction Events during the Last 5 Million Years

A.Earth’s Early History -Earth formed about 4.6 billion years ago. -Earth’s early atmosphere was very different and contained almost no free oxygen.

B.The Geologic Time Scale

1.Precambrian (4,600 – 542 MYA) -Life (prokaryotes) probably began 3.5 billion years ago. -Photosynthesis evolved ~ 3 billion years ago. Ediacaran Seascape

2.Paleozoic Era ( MYA) - Cambrian explosion marks appearance of most phyla of living animals. A Cambrian Seascape

3.Mesozoic Era ( MYA) - Age of dinosaurs (& conifers) - Emergence of coral reefs Coastal Cretaceous Scene

4.Cenozoic Era (65 MYA- Present) - followed the mass extinctions of many terrestrial and marine animals The real reason dinosaurs went extinct

4.Cenozoic Era (65 MYA- Present) - followed the mass extinctions of many terrestrial and marine animals The Cretaceous mass extinction was probably caused by a meteorite and led to the extinction of the dinosaurs.

- Age of mammals -Insects and flowering plants diversified A Pleistocene Environment

WASP IN AMBER C.Clues in Rocks 1.Fossils - any preserved remains of a once-living thing - examples: PETRIFIED BONE PETRIFIED LOG SLOTH IN TAR PIT IMPRINT

2.Fossil Formation a.An organism dies quickly and is buried under sediments. b.Sediments build up over the years. c.Pressure causes mineralization (organic tissues replaced by mineral deposits).

3.Dating Fossils a.Relative Dating - Law of Superposition: rocks (and fossils) contained in upper layers are younger than those found in lower layers

b.Radiometric Dating - determining the age of rock or fossils by measuring the rate of decay radioisotopes such as Carbon-14, Uranium-238

-Evidence suggests a sequence of chemical events lead to the origin of the first cells. -Life has continuously evolved since then. Land plants Animals Multicellular eukaryotes Single-celled eukaryotes Atmospheric oxygen Prokaryotes Origin of solar system and Earth Humans Ceno- zoic Meso- zoic Paleozoic BYA II.The Origins of Life

A.Early Ideas 1.Spontaneous Generation - The idea that life could arise from nonliving things. Wheat Open-mouthed Jar Sweaty Underwear 21 Days Mice “Recipe” for Mice (1698)

Toads from emerging from the soil A.Early Ideas 1.Spontaneous Generation Barnacle Goose Tree

Francesco Redi’s Experiment 2.Biogenesis - Spontaneous generation disproved by F. Redi (1668) and Louis Pasteur (1859). - Living organisms come only from other living organisms.

2.Biogenesis - Spontaneous generation disproved by F. Redi (1668) and Louis Pasteur (1859). - Living organisms come only from other living organisms. Louis Pasteur’s Experiment

Electrode Condenser Cooled water containing organic molecules H2OH2O Sample containing amino acids and other organic compounds Cold water Water vapor CH 4 H2H2 NH 3 B.Modern Ideas -Miller and Urey (1953) showed that simple organic molecules could spontaneously form from inorganic compounds.

DNA Plasma membrane Ancestral prokaryote Infolding of plasma membrane Endoplasmic reticulum Nuclear envelope Nucleus Engulfing of aerobic heterotrophic prokaryote Cell with nucleus and endomembrane system Mitochondrion Ancestral heterotrophic eukaryote Plastid Mitochondrion Engulfing of photosynthetic prokaryote in some cells Ancestral Photosynthetic eukaryote C.Endosymbiotic Theory - Mitochondria and chloroplasts probably originated as free- living prokaryotic cells. - Both organelles have their own DNA and ribosomes distinct from eukaryotic host cells. - Both reproduce independently from host cells.

The End Triassic Landscape, Karen Carr