•morphologists: interested in structures and function•evolutionary biologists: support for evolutionary theory•systematists: interested in phylogenetic relationships of extant and extinct animals•paleontologists: interested in structures for identification of extinct animals

Who studies paleontology?

HOMOLOGY vs. ANALOGY

Homology: share a recent common ancestor

Homologies are established by:•fossil record, historical biogeography•embryology, comparative anatomy (e.g., topographic location)•genetics (DNA, molecular sequence data)

Homologous structures do not have to look alike (e.g., bird beaks, feet, or feathers) but they do share a recent common ancestor.

Analogy: shared function, but no recent common ancestor

Analogous structures often appear similar (superficially) because of their functione.g., penguin wing / dolphin fin shark fin / ichthyosaur fin

Slide of the rock cycle and importance of sedimentary rocks to the rock record and fossilization.

The Rock Cycle

Fossils are found in Sedimentary Rocks. The rocks can be:•detrital: physical break down of pre-existing rocks•chemical: produced by chemical precipitating dissolved minerals out of solution.

The minerals are in solution from chemical weathering of preexisting rocks.

Transportation and deposition processes: ice (glaciers), water (rivers, streams, oceans), and air (loess).

Transportation is related to the amount of energy in the system.

Depositional Environments•Continental environments: e.g., fluvial, desert, glacial•Transitional environments: e.g., beach, delta, barrier islands.•Marine environments: e.g., continental shelf, carbonate platform, continental slope and rise, deep-ocean basin, evaporite environments.

Paleoenvironmental interpretations are based upon the evidence found in the rocks, e.g., organisms, niche, habitat, water depth, etc.

Different environmental settings form little or no deposits, while other deposits become soils. Lithification is the process of compaction and/or cementation.

Sandstone

Sand is a particle size and sandstone is a composite.

Most sandstone is made up of quartzand a few other minerals.

For minerals to become sedimentary rock they must be available, mechanically durable, and chemically stable.

Typical sedimentary rock facies include: sand facies, mud facies, and carbonate (limestone) facies.

Marine transgressions and regressions are major worldwide events that are recorded in the rock record. They are used to hypothesize correlations of eustatic sea levels (rise and fall).

Examples of sedimentary structures are: strata or beds, graded beds, paleo-currents, and mud cracks.

Fossils are found in an altered condition, e.g., permineralized and an unaltered condition, e.g., mummification. Types of fossils can be body or trace fossils or coprolites. Fossilization as a process includes: petrified, permineralization, and carbonized.

Requirements for permineralization include: rapid burial, mineral rich water percolating through the sediments, and time.

Erosion exposes fossils to a trained observer.

Geologic Time

Relative versus Absolute time

Fundamental principles of relative time are the principle of uniformitarianism, superposition, lateral continuity,

cross-cutting relationships, inclusion, and fossil succession.

Principles of relative dating and the geologic maps explain ideas like correlation and include key beds and guide fossils.

Geologic maps also include information, e.g., unconformity (disconformity, angular unconformity, and nonconformity) and what is a hiatus (missing data).

Relative versus Absolute Time

Fossil Succession

Lateral Continuity

Singular History of Life on Earth

Origin of Life

3800 Million Years Before Present

Submarine Hydrothermal Vent

Age of Stromatolites2500 Million Years Before Present

Prokaryotic and Eukaryotic Cells

Major Episodes in the History of Life