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Geology F795 > Microfossils > Flashcards

Flashcards in Microfossils Deck (17):

Why are microfossils useful?

Can be used to correlate rocks, well preserved and show strong evolutionary trends


What are Ostracods?

Complex crutaceans, two valves with teeth and sockets, car pace shell of chitin are calcite


Range of Ostracods?

Cambrian to present


How can ostracod fossils be used?

Long statigraphic range which limits use as zone fossil, paleoenvironment indicators as have different forms in water of different salinity


What are Forminfera?

Single called creatures, protective test, early forms glued together, feed via thread like structures, most Benthonic


Time range of Forminfera

Cambrian to present


How can Forminfera be used?

Stratigraphic tool used extensively in oil industry, detailed ranges can be determined for differ species, provide evidence for evolution


What are conodonts?

Teeth of soft bodies creature, calcium phosphate, occur in pairs, found in Precambrian ricks to Permo-Triassic extinction


What are Radiolaria?

Marine, planktonic organism, composed of silica, occupy niches near surface to hundred of m depths, rich diversity, preserved below CDC


Range of radiolaria?

Precambrian to present


How are spores and pollen preserved?

Tough, composed of sporopollenin, found from Ordovician onwards, pollen from late Devonian. Produced by plants in land or in shallow water, washed out to sea so found in lots of environments


How does evolution occur?

Phyletic gradualism, characteristics change by mutation and cross breeding, favoured by natural selection


What is gradualism?

Gradual evolutionary change over time, creation of new characteristics it genes


What is genetic drift?

Few selective pressures, random sampling of parent genotype can eventually lead to elimination of some characteristics


What is gene flow?

Exchange of genes between populations by migration or pollination


What is punctuated equilibrium?

For long periods no change occurs as population expands, at limits of environment, population forced to adapt and new species takes over quickly


Why are microfossils better for proving evolution than microfossils?

Small and abundant in rocks, tend to be better preserved