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Lecture 18

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Department
Biology
Course
Biology 1001A
Professor
Tom Haffie
Semester
Fall

Description
Chapter 20.2, 20.4, 20.6 (Lecture 18) 20.2- Changes in Earth • Plate tectonics can be responsible for phenomena such as continental drift and have strong influences on the distribution and evolution of organisms • Changes in Earth’s crust can also cause calamitous events, such as earthquakes, which also have implications for living organisms Patterns in macroevolution • The fossil record • Mode and tempo evolution • Evolutionary trends: changes in body size 20.4- The Fossil Record • Most fossils are found in sedimentary rocks • Conditions of low oxygen or high acidity are ideal for fossilization. • Hard structures such as skeletons and teeth do not readily decompose and are more often fossilized than softer structures. o Some fossils are casts or moulds; in others, the original materials are replaced by dissolved minerals • The availability of fossils is highly skewed toward certain areas, certain organisms, or parts of organisms • Scientists can assign relative and absolute dates to geological strata and the fossils they contain o Sequence of fossils in the lowest (oldest) to the highest (newest) strata reveals their relative ages o Radiometric dating is based on the decay rates of unstable isotopes and permits absolute dating (half-lives) • Fossil Record is incomplete and biased o Most species have never formed fossils o Biases in fossil record  Temporal- more likely to find new fossils than old fossils due to erosion, etc.  Taxonomic- not everything is likely to fossilize  Habitat- Some environments are better for fossil formation i.e. ocean good environment 20.6- Interpreting Evolutionary Lineages • The evolution and adaptive radiation of horses demonstrate that many species arise
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