Radioisotopes.docx

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Department
Biomedical Engineering
Course
BMEN 515
Professor
William Huddleston
Semester
Fall

Description
 Fossils- the preserved remains of ancient organisms  Paleontologists- scientists who study fossils  Morphology- the body form  Age of rocks cannot be determined by just looking at them, but the age of rocks can only be determined when comparing one another  Strata- oldest layers in rocks; are known to lie at the bottom, and successively higher strata are progressively younger  William Smith concluded that: o Fossils of similar organisms were found in widely separated places on Earth o Certain organisms were always found in younger rocks than certain other organisms o Organisms found in higher, more recent strata were more similar to modern organisms than were those found in lower, more ancient strata Radioisotopes  Radioactivity- a method of dating rocks; discovered at the beginning of the twentieth century  Half-Life- a successive time interval in which half of the remaining radioactive material of the radioisotope decays, either changing into another element or becoming the stable isotope of the same14lement  For C, production in the upper atmosphere is about equal to its natural decay.  In an organism, the ratio of C to C stays constant during its lifetime. 14  When14n organism dies, it is no longer incorporating C from the environment. 14 12  The C that was present in the body decays with no replacement and the ratio of C to C decreases.  As soon as an organism dies, it ceases to exchange carbon compounds with its environment  Isotopes in a sedimentary rock do not contain reliable information about the date of its formation o Since they are transported over long distances and are deposed in another location  But igneous rocks (e.g., lava or volcanic ash), that have intruded into layers of sedimentary rock can be dated.  Other radioisotopes are used to date older rocks.  Decay of potassium-40 to argon-40 is used for the most ancient rocks.  Radioisotope dating is combined with fossil analysis.  Lithosphere- is Earth’s crust which consists of a number of solid plates each about 40 kilometers thick o Floats on a fluid layer of molten rock or magma; the magma circulates because heat produced by radioactive decay deep in Earth’s core sets up convection currents in the fluid  The plates move because magma rises and exerts tremendous pressure  Where plates are pushed together, either they move sideways past each other, or one plate slides under the other, pushing up mountain ranges and carving deep rift valleys (when they occur under water, such valleys are known as trenches)  Where plates are pushed apart, ocean basins may form between them  Continental Drift- movement of the lithospheric plates and the continents they contain  Throughout Earth’s history, the plates that carry the continents have drifted apart and moved back together numerous times.  Plate movement has affected climate, sea level, and the distribution of organisms. Increase of Oxygen in Atmosphere  Increase in atmospheric oxygen have been largely unidirectional  Oxygen first in atmosphere 3.8 bya (billion years ago)  Oxygen concentrations began to increase significantly about 2.4 billion years ago when some prokaryotes evolved the ability to split water as a source of hydrogen ions for photosynthesis. The waste product is O .2  One lineage of these oxygen-generating bacteria evolved into the cyanobacteria. These organisms formed rocklike structures called stromatolites.  The cyanobacteria liberated enough O to a2low the evolution of oxidation reactions as the energy source for the synthesis of ATP  When oxygen first appeared in the atmosphere, it was poisonous to the anaerobic prokaryotes that inhabited Earth at the time  Organisms with aerobic metabolism replaced anaerobes in most of Earth’s env
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