BIOEE 1780 - Macroevolution 1

Absolute Dating

Determining the number of years that have elapsed since an event occurred or the specific time when that event occurred

Daughter Isotope

The isotope that forms as a result of radioactive decay

Half-life

The amount of time it takes for half of the parent isotopes to radioactively deca to daughter isotopes

Index Fossil

A fossil that can be used to determine the age of strata in which it is found and to help or relate between rock unit

Isoptopes

Varieties of the same element that have the same number of protons, but different numbers of neutrons

parent isotopes

the atomic nucleus that undergoes radioactive decay

potassium-argon (K-Ar) method

Radiometric dating technique that uses the decay of 39K and 40 Ar in potassium-bearing minerals to determine the absolute age

principle of cross-cutting relationship

any geological feature that ross-cuts across strata must have formed after the rocks they cut through were deposited

principle of faunal succession

fossil species succeed each other in a definitive, recognizable order and once a species goes extinct, it disappears and cannot reappear in younger rocks

principle of original horizontality

Layers of strata are deposited horizontally or nearly horizontally, and once a species goes extinct it disappears and cannot reappear in younger rocks

principle of superposition

in a undeformed sequence, the oldest rocks are at the bottom and the youngest are at the top

radioactive decay

the process by which unstable isotopes transform to stable isotopes of the same or different elements by a change in the number of protons and neutrons in the atomic nucleus

radiocarbon dating

radio metric dating technique that uses the decay of 14C in organic material, such as as wood or bones, to determine the absolute age of the material

relative dating

rocks and structures are placed into chronological order, establishing the age of one thing as older or younger than another

strata (singular: stratum)

Distinct layers of sediment that accumulated at the earths surface

stratigraphy

the study f strata and their relationships

Fossil

Fossils are remains or traces of once living organisms

Ordinary Conditions impede fossilization

Predators and Scavengers

Bacterial Decay

Dissolution in water

Physical Disturbance (e.g. wave action, wind)

Special conditions promote fossilization

Rapid Burial

Protection from physical disturbance e.g, quiet, deep water

Anaerobic environment (prevent bacterial decay)

What gets preserved? (Animal)

Hard parts comprise most of the record (Bone, teeth, exoskeletons)

What gets preserved? (Plant)

seeds, pollen, leaves, wood, rarely flowers

What gets preserved? (microbes)

Bacteria, microbial mats

Original remains

Contain the most information

Permineralization

Retains structure

• Pores in plants, bone, shells with minerals from solution (silica, alliteration, iron)

Trace Fossils

Trace left by organisms

• Footprint, rodent burrow, root marks, mollusk trails

Impression Fossils

Only carbonaceous film

• a silhouette of carbon left

Lagerstatten

Spectacular fossil assemblages preserved in really favorable environments and gives a lot of info

The Burgess Shale, Canada, Cambrian

Preservation of soft tissues by rapid burial, anoxic conditionals (avalanche of fine mud mud into deep water)

• Helps us understand Cambrian explosion

• Avalanche of mud, burying animals in deep water

Lateral Continuity

Layers continue laterally over distances

Geological chronology

How do we know the age of the fossil?