BSC2010 - Chapter 17

Igneous rock

volcanic

sedimentary rock

sand, soil

Metamorphic rock

rocks formed by pressure

Fossils form in … rock

sedimentary

formation of a fossil

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.

best preserved fossils

aquatic organisms with hard skeletons

relative dates

younger layers are deposited on top of older, fossils appears in the same order in different outcrops

Igneous (volcanic) rock contains …

radioisotopes that are used for dating sedimentary strata & the fossils they contain

half life

the time in which ½ of the remaining radioisotope decays (changing into another element

carbon dating

measuring the ratio of parent to daughter atoms allows us to determine how long since the rock was formed

plate tectonics

geophysics of the movement of land masses

Early atmosphere had little to no

O2

First life was…

anaerobic until photosynthesis evolved

increase in O2 led to

evolution of aerobic bacteria

Precambrian era (4.5 bya - 542 mya)

for most of this era, life consisted of microscopic prokaryotes living in oceans, life first appeared about 3.8 by a. Eukaryotes evolved about 1.5 bya

Paleozoic Era: Cambrian period (542-488 mya)

similar to O2 concentration today, the Cambrian explosion was a rapid diversification of multicellular life

Paleozoic Era: Ordovician period (488-444 mya)

• radiation of marine organisms, especially brachiopods and mollusks

• ended w/ a mass extinction due to massive glaciation event and lowered sea levels

Paleozoic Era: Silurian period (444-416 mya)

• marine life rebounded, first jawed fish

• vascular plants appeared, as well as some terrestrial scorpions and millipedes

Paleozoic era: Devonian period (416-359 mya)

• Age of fishes

• Forest appeared:club mosses, horsetails, tree ferns, common; first seed plants

• Earliest insect, spider, and amphibian fossils (first tetrapod)

• major extinction event for marine species

Paleozoic era: carboniferous period (359-297 mya)

• glaciers at high latitudes and expansive swamp forests in tropics, later became fossilized as coal

• Winged insects; amphibians diversified; origin of amniotes - vertebrates with shelled eggs

Paleozoic Era: Permian period (297-251 mya)

• continents came together to form the super-continent Pangaea

• amniotes split into reptilian & mammalian lineages

• ended with the greatest mass extinction in Earth’s history

The great dying

96% of all multicellular species became extinct, likely due to volcanic activity that led to climate cooling, glaciers, and sea-level drops.

Atmospheric O2 declined, making land above 500 m uninhabitable for animals

Siberian Traps

massive volcanic activity in Large Igneous Provinces (LIP) may have role in major extinctions at end of Permian

Mesozoic Era: Triassic period (251-200 mya)

• Pangaea began to break apart

• conifers and seed plants dominant on land

• radiation of reptiles

• ended in mass extinction (60%)

Mesozoic era: jurassic period (200-145 mya)

• Pangaea divided into Laurasia, which drifted north, and Gondwana, which drifted south

• lizards and flying reptiles (pterosaurs) appeared; most large terrestrial animals were dinosaurs

• flowering plants and several mammal groups appeared

Mesozoic Era: Cretaceous period (145-65 mya)

• earth was warm and humid

• dinosaurs and flowering plants radiated; first snakes

The K-T boundary

another mass extinction at the end of the cretaceous was caused by a meteorite, on land, all animals >25 kg and many insects became extinct

Cenozoic Era: Tertiary period (65-2.6 mya)

• climate was become cooler and drier. Grasslands spread.

• Radiations of flowering plants, snakes, lizards, birds, and mammals

Cenozoic Era: Quaternary period (2.6 mya-present)

• pleistocene & holocene epochs

• Multiple “ice ages” continental glaciers spread, shifting species ranges

• hominid evolution and radiation

• many large mammal species went extinct in Australia and the Americas when Homo sapiens arrived.

Ice ages

continental glaciers spread, shifting the ranges of plants and animals

Pleistocene overkill

many large mammal species became extinct in Australia (45,000 ya) and the Americas (15,000 ya) when Homo sapiens arrived- possibly due to hunting pressure.

mass extinction

defined by the loss of at least 75% within a short period of time (geologically, this is around 2 million years)