101 Chapter 8 Notes
Fossils: Memories of the Biological Past
What are fossils?
Fossils are the remains of organisms chemically changed into rock.
Taphonomy and Fossilization
Taphonomy is the study of what happens to an organism’s remains after death.
Describes what circumstances are necessary for fossilization to occur.
Fossilization requires an anoxic environment, where decomposition is limited.
Limitations of the Fossil Record: Representation Is Important
The fossil records present a “snapshot” of life in the past.
Recognition of this limitation is critical in interpreting the fossil record.
The best preservation of early human primates is in east & south Africa after 4 mya.
Just How Old is the Past?
Time in perspective
Long expanses of time that paleontologist handle (e.g., millions of years) are difficult for
many people to conceive.
It is necessary to place fossils in time and space to fully understand their significance.
Relative Methods of Dating
Stratigraphic Correlation
Relative age is determined by comparing the incidence of one event to another.
Those at the bottom of a stratum are older than those nearer the top.
Fluorine Dating
Flourine dating measures levels of fluorine in bones to determine relative age.
Dragutin Goranovic developed the fluorine dating technique and later proved that
Neandertals cooexisted with extinct mammals.
Biostratigraphic (Faunal) Dating
Faunal dating compares different fossil forms based on the first appearance of an
organism through its extinction
Cultural Dating
Cultural Dating uses changes in material culture (such as stone tools) to establish
a chronology
Absolute Methods of Dating: What Is the Numerical Age?
Absolute (numerical) age is determined through methods that result in a numerical scale.
Dendrochronology counts the rings of trees
Each ring marks one year of growth.
Radiocarbon Dating
Radiocarbon dating measures the half-life of carbon isotopes.
This method is accurate for only the last 50,000-70,000 years ago.
Can only date organic material (bone, wood, shell, fiber, etc.)
Radiopotassium Dating
Radiopotassium dating measures the potassium radioisotope in volcanic rock
associated with fossils
Potassium has a long half-life, used to date fossils older than 200,000 years.
Reconstruction of Ancient Environments and Landscapes
In addition to constructing time scales, researchers also try to reconstruct ancient
environments.
The Driving Force in Shaping Environment: Temperature
Temperature drives climate, which is linked to biology and chemistry.
Ancient temps are reconstructed through study of ocean dwelling organisms.
One of the most dramatic changes in temperature occurred around 6 mya and was
a cooling period in Earth’s history.
Chemistry of Animal Remains and Ancient Soils: Windows onto Diets and Habitats
Chemical analysis of bones and teeth can reconstruct diets and habitats based
on plants the animals ate.
Different environments are associated with different types of carbon dioxide
(e.g., C3 or C4).
Time, space, habitat, and diet are important factors in the interpretation of the
fossil record.