The Fossil Record Provides evidence about the history of life on Earth. It also shows how different groups of organisms, including species, have changed over time.

Relative Dating Can determine Is performed by Drawbacks Absolute Dating Comparing Relative and Absolute Dating of Fossils Imprecision and limitations of age data Difficulty of radioassay laboratory methods Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock Determining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimen Age of fossil with respect to another rock or fossil (that is, older or younger) Age of a fossil in years Relative vs. Absolute Dating

Principle of Superposition In an undisturbed sequence of sedimentary rocks, the oldest rocks are on the bottom with the most recent on top.

How fossils are formed Water carries small rock particles to lakes and seas. Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied.

Geological Time Scale After the Precambrian Time, the time scale is divided into eras, which are subdivided into periods. EraPeriodTime Permian Carboniferous Devonian Silurian Ordovician Cambrian (millions of years ago) EraPeriodTime (millions of years ago) EraPeriodTime (millions of years ago) 290 – – – – – – –present 65– –65 208– –208 Quaternary Tertiary Cretaceous Jurassic Triassic Vendian650–544

Geological Time Scale The major eras are Paleozoic, Mesozoic, and Cenozoic. EraPeriodTime Permian Carboniferous Devonian Silurian Ordovician Cambrian (millions of years ago) EraPeriodTime (millions of years ago) EraPeriodTime (millions of years ago) 290 – – – – – – –present 65– –65 208– –208 Quaternary Tertiary Cretaceous Jurassic Triassic Vendian650–544

Geologic Time Scale Each period hosts significant evolutionary changes to species diversity and extinction. EraPeriodTime Permian Carboniferous Devonian Silurian Ordovician Cambrian (millions of years ago) EraPeriodTime (millions of years ago) EraPeriodTime (millions of years ago) 290 – – – – – – –present 65– –65 208– –208 Quaternary Tertiary Cretaceous Jurassic Triassic Vendian650–544

Glaciations; mammals increased; humans Mammals diversified; grasses Aquatic reptiles diversified; flowering plants; mass extinction Dinosaurs diversified; birds Dinosaurs; small mammals; cone-bearing plants Reptiles diversified; seed plants; mass extinction Reptiles; winged insects diversified; coal swamps Fishes diversified; land vertebrates (primitive amphibians) Land plants; land animals (arthropods) Aquatic arthropods; mollusks; vertebrates (jawless fishes) Marine invertebrates diversified; most animal phyla evolved Anaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life Cenozoic Mesozoic Paleozoic Precambrian Time Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian 1.8–present 65– –65 208– – – – – – – – –544 Key EventsEraPeriodTime (millions of years ago) Summary of major events (pg )

Hypothesis of early Earth Very hot surface from colliding meteorites Very hot planet core from radioactive materials Volcanoes spewing lava and gases that helped to form the early atmosphere

Hypothesis of early Earth About 4.4 billion years ago, Earth might have cooled enough for the water in its atmosphere to condense. This might have led to millions of years of rainstorms with lightning, enough rain to fill depressions that became Earth’s oceans. The oldest rocks dated are 3.9 million years old.

Fossils: evidence of an organism that lived long ago that is preserved in Earth’s rocks Paleontologists estimate that about 95% species are extinct from life’s origins. Climate and ancient geography can be determined from fossils. Fossils Types Formation Trace fossils Casts Molds Petrified/ Permineralized fossils Amber- Preserved or frozen fossils A trace fossil is any indirect evidence left by an animal and may include a footprint, a trail, or a burrow. When minerals in rocks fill a space left by a decayed organism, they make a replica, or cast, of the organism. A mold forms when an organism is buried in sediment and then decays, leaving an empty space. Petrified-minerals sometimes penetrate and replace the hard parts of an organism. Permineralized-void spaces in original organism infilled by minerals. At times, an entire organism was quickly trapped in ice or tree sap that hardened into amber.

What has been learned from fossils several episodes of mass extinction that fall between time divisions –mass extinction: an event that occurs when many organisms disappear from the fossil record almost at once The geologic time scale begins with the formation of Earth about 4.6 billion years ago.

Precambrian – 87% of history Oldest fossils about 3.4 billion years old resembling cyanobacteria stromatolites. Stromatolites still form today in Australia from mats of cyanobacteria. The stromatolites are evidence of the existence of photosynthetic organisms on Earth during the Precambrian. Only prokaryotic life found in fossil record

End of Precambrian – 543 MYA multicellular eukaryotes, such as sponges and jelly-fishes, diversified and filled the oceans

Paleozoic and Cambrian Period Paleozoic Era: more animals and plants –Early: fishes, aquatic vertebrates, ferns –Middle: amphibians –Late: reptiles and mass extinction –Cambrian Period: oceans teemed with many types of animals, including worms, sea stars, and unusual arthropods

Mesozoic MYA Triassic Period: mammals and dinosaurs Jurassic Period: dinosaurs and birds Cretaceous Period: more mammals, flowering plants, but mass extinction of dinosaurs 65 MYA

Continental drift Earth’s continents have moved during Earth’s history and are still moving today at a rate of about six centimeters per year. The theory for how the continents move is called plate tectonics.

Miller-Urey experiment showed one possible way for inorganic molecules to form organic molecules. Mixture of gases simulating atmospheres of early Earth Spark simulating lightning storms Condensation chamber Cold water cools chamber, causing droplets to form Water vapor Liquid containing amino acids and other organic compounds

How eukaryotic cells evolved Lynn Margulis proposed the endosymbiotic theory. Aerobic bacteria Ancient Prokaryotes Ancient Anaerobic Prokaryote Primitive Aerobic Eukaryote Primitive Photosynthetic Eukaryote Chloroplast Photosynthetic bacteria Nuclear envelope evolving Mitochondrion Plants and plantlike protists Animals, fungi, and non-plantlike protists

Endosymbiotic theory Heterotrophic bacteria have plasmids (DNA loop) & simple ribosomes in their cytoplasm Mitochondria have circular DNA & bacteria-like ribosomes So…Eukaryotic cells may have engulfed prokaryotic cells & by mutualism created the “first mitochondria.”

Autotrophic bacteria are Cyanobacteria with chlorophyll So, Eukaryotic cells may have engulfed prokaryotic cyanobacteria & by mutualism created the “first chloroplast.”

Macroevolution  Large-scale evolutionary patterns and processes that occur over long periods of time.  Includes 6 topics:  Extinction  Adaptive radiation  Convergent evolution  Divergent evolution  Punctuated equilibrium  Changes in developmental genes

Patterns of evolution Darwin believed that organisms evolved gradually. Niles Eldredge and Stephen Jay Gould believed punctuated equilibrium is how organisms evolved, periods of rapid evolution followed by periods of stasis.

Adaptive Radiation Single species or small groups of species evolved into diverse forms living in different ways.

Convergent Evolution Adaptive radiation can produce unrelated organisms that look similar due to similar environments.

Coevolution Example: “This butterfly acquires a cardiac glycoside from members of the genus Asclepias. Because of their milky sap, these are commonly referred to as milkweed plants. The plants produce this toxin as a defense against herbivory, but the Monarch has the ability to sequester the toxin in fatty tissues so that it makes the butterfly unpalatable while not poisoning the butterfly.” ecologyf02 The process by which two species evolve in response to changes in each, other over time.