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FossGeo
Fossils and Geological Timeline
| Question | Answer |
|---|---|
| It is estimated that less than ____ of all the species that have inhabited this Earth are still alive today. | 1% |
| When the last member of a species dies that species is said to be __________ | extinct |
| Geologic changes such as earthquakes, volcanoes, floods, changes in climate, and asteroid impacts are all possible explanations for _____ __________ | past extinctions |
| organic evolution must follow __________ ___________ or extinction will result | geologic evolution |
| Paleozoic Era | Cambrian Period—500-600 million years ago, The first shelled animals (brachiopods) |
| The Cambrian Explosion | a burst of diversification unmatched in the history of the world. All modern animal phyla represented although not in their current form. |
| Ordovician Period | 440-500 million years ago - The first vertebrates-primitive fish appear |
| Silurian Period | 395-440 million years ago - The first true land plants appear, First air-breathing land animals |
| Devonian Period | 345-395 million years ago |
| Carboniferous Period | 280-345 million years ago - Amphibians dominant while the first reptiles appear Spiders, cockroaches, and scorpions appear The first land-dwelling animals |
| Permian Period | 225-280 million years ago - Amphibians decline while reptiles become abundant Modern insects appear Trees similar to the pine develop |
| Triassic Period | 190-225 million years ago - Beginning of the dinosaurs-plant eaters, meat eaters, flying reptiles, and crocodiles First mammals and bony fishes |
| Jurassic Period | 136-190 million years ago - Giant dinosaurs developed Abundant plant life-conifers and cycads. Flowering plants appear |
| Cretaceous Period | 65-136 million years ago - Peak of development as well as the downfall of the dinosaurs Small marsupials, toothed birds, and modern fish appear Conifers decrease while flowering plants increase. Deciduous trees appear |
| Tertiary Period | 2-65 million years ago - Early placental mammals appear along with modern birds Mammals such as camels, bears, cats, monkeys, rodents, and dogs appear. Grasses and fruits very similar to those we have today develop. |
| Quaternary Period | 2 million years ago-present More mammals develop including the Saber-Toothed Tiger and Mastadon (now both extinct) Modern man appears |
| the extinction of all the dinosaurs at the end of the Cretaceous period ____ __________ years ago. | 65 million |
| What periods are in the Paleozoic Era? | Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian |
| What periods are in the Mesozoic Era? | Triassic, Jurassic, Cretaceous |
| What periods are in the Cenozoic Era? | Tertiary, Quaternary |
| Paleontologist | One who studies fossils Science founded by George Cuvier (1769-1832) an English vertebrate zoologist |
| Dinosaurs at the end of the Cretaceous Period | Example of a mass extinction |
| Define the Imprint Fossil Type | impressions left in mud harden into rock (leaves, feathers, footprints) |
| Define the Mold Fossil Type | the remains of an organism decay but leave a hollow depression outlining the size and shape of the organism |
| Define the Cast Fossil Type | formed when the mold filled with sediment and hardened to form a copy of the external features of the organism |
| Define the Petrifaction Fossil Type | organisms die and lie in a body of water with a high mineral content. Eventually the organism decays, dissolves, and its body is replaced with minerals which turn to stone |
| Define the Intact Fossil Type | whole remains or parts are preserved in tar, amber, ice, etc. |
| Relative Dating Method: | relative age may be determined by a fossil’s relative position in sedimentary rock layers or strata, Older fossils found in deeper strata Newer fossils nearer the surface Layers of sediment form at about 30cm/1,000 years |
| ____________ had a very distinctive shell pattern often seen as a mold fossil. They only lived during a finite period from 500-600 million years ago | Trilobites |
| Absolute Dating Method | Method to determine the actual age of a fossil Ex. C-14 dating Some radioactive isotopes have unstable nuclei that breakdown or decay over time giving off radiation. The rate of decay is constant or fixed and unaffected by physical conditions. |
| Radioactive Dating Method | Half-life = time it takes for half the atoms of an isotope to decay Half-life of C-14 = 5,700 years So, if a fossil were found containing ½ the original amount of C-14 it would be 5,700 years old. |
| Carbon Dating Method | There is always a mixture of C-12 and C-14 in the atmosphere and thus reflected in the organism. Once the organism dies, it stops taking in carbon and radioactive decay begins. |
| With carbon dating, we are comparing ____ to its own decay product ______. Therefore the more N-14, the more __________ decay, the ________ the fossil | C-14, N-14, radioactive. older |
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