The layers are young at the top and older at the bottom
How can the ACTUAL ages of rocks be determined?
How do radioisotopes decay?
In a predictable pattern.
What is a half life?
The time in which 1/2 of the remaining radioisotopes decay and change into another element
How did old geologists develop a time scale?
Using various dating methods and fossil stratigraphy
How is the history of life divided?
Into ERAS which are then divided into periods
Why is the fossil record incomplete?
Organisms decompose quickly; they can fossilize when there is little or no oxygen, marine animals with shells or exoskeletons are more likely to leave fossils.
Why are some fossils destroyed?
Many geological processes transform the rocks and destroy the fossils or they are buried and are too deep to reach
Are all animals fossilized and found?
No, only a small fraction of organisms become fossils, and an even smaller fraction of those fossils are found by paleontologists.
Can the incomplete fossil record tell the history of life on earth?
Yes, although it is incomplete, it does contain enough information.
What is the continental drift/plate tectonics idea?
Positions of the continents have changed over time, they shape the position and size of continents and influence ocean circulation patterns, global climate, and sea level
What do dramatic geological changes result in?
How can large volcanic eruptions have effects on the planet?
Ash and SO2 are released into the atmosphere blocking sunlight and resulting in cooling of the planet which can then lead to glaciation and a drop of sea level (since the water is freezing) and finally a mass extinction.
How did O2 first increase?
When cyanobacteria evolved photosynthesis (2.4 bya)
Where are stromatolites found and what formed them?
They are abundant in fossil records and formed by cyanobacteria
What did the O2 released by cyanobacteria allow?
The evolution and oxidation of reactions as the energy source for ATP synthesis
After the initial introduction to O2 into the environment, how did cyanobacteria increase the levels again?
The cyanobacteria were incorporated into eukaryote host cells as chloroplasts evolved
What happened to the anaerobic organisms after the introduction of O2?
They were replaced by aerobic organisms.
In larger and more complex organisms, how is surface area:volume?
They require higher O2 concentrations and have lower surface area:volume ratios
When was the precambrian Era?
4.4 bya - 542 mya
How was the precambrian era? What did life consist of?
It consisted of microscopic prokaryotes living in oceans
When did life first appear? What era?
3.8 bya; during the during the precambrian era
When did eukaryotes first evolve? During what era?
Precambrian, 1.5 bya
What kinds of animals evolved in the precambrian era?
Many multicellular soft-bodied animals, very different from the ones today
During what period did the rapid diversification of life, known as an evolutionary radiation, take place?
The Cambrian explosion, in the cambrian period in the paleozoic era
How was the O2 concentration in the cambrian period in the paleozoic era?
Describe the Ordovician period in the Paleozoic era? How long ago? How did it end?
488-444 mya; radiation of marine organisms (brachiopods and mollusks), ended with mass extinction because of massive glaciers and lowered sea levels.
Describe the Silurian Period in the paleozoic era. How long ago?
444-416 mya; marine life rebounded, vascular plants appeared, some terrestrial scorpions and millipede
Descibe the Devonian period in the Paleozoic era. How long ago?
416-359 mya. Age of fishes, club mosses, horsetails, tree ferns, first seed plants, earliest insect, spider, and amphibian fossils.
Describe the Carboniferous period in the paleozoic era. How long ago?
359-297 mya; glaciers at high atitudes, swamp forests on tropical continents (fossilized as coal), winged insects, amphibians diversified, origin of amniotes
Describe the permian period in the paleozoic era. How long ago?
297-251 mya, continents came together and formed pangea, amniotes split into reptiles and mammals.
How did The permian end?
With the greatest mass extinction in the earth's history. 96% of all speices became extinct.
What is believed to be the cause of the End-Permian event?
Massive volcanoes that led to climate cooling, glaciers, and low sea levels causing drop of atmospheric oxygen and making land over 500m uninhabitable
Describe the triassic period in the mesozoic era. How long ago?
251-200 mya. Pangea broke apart. Conifers and seed plants dominated. Radiation of reptiles (crocs, dinosaurs, and birds)
Describe the jurassic period in the mesozoic era. How long ago?
200-145 mya. Pangea divided into LAURASIA in the north and GONDWANA, which drifted south. Lizards and flying reptiles (pterosaurs), most large terrestrial animals were dinosaurs. Flowering plants and mammalian groups appeared.
Describe the cretaceous period in the mesozoic era. How long ago?
145-65 mya. Earth was humid and warm while dinosaurs and flowering plants radiated. First snakes
When did the K-T boundary mass extintion happen? What caused it?
During the cretaceous period; caused by a meteorite
What is evidence that the K-T boundary mass extinction was caused by a meteorite?
A thin rock layer with high iridium content and a huge impact crater beneath the northern coast of the yucatan peninsula, extincting all animals larger than 25kg on land and many insects.
Describe the tertiary period in the cenozoic era. How long ago?
65-2.6 mya. Climate was cooler and drier, grasslands spread. Radiation of flowering plants, snakes, lizards, birds, and mammals.
Describe the quaternary period in the cenozoic era. How long ago?
2.6 mya- present. During Pleistocene ice ages, continental glaciers spread shifting species ranges. Hominid evolution and radiation, many large mammals went extinct in Australia and the Americas when Homo sapiens arrived.