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