Fossils

Earth's Eras

Precambrian, Paleozoic, Mesozoic, Cenozoic

Shortest Era

Cenozoic era

Longest Era

Precambrian Era

How are the boundaries between eras defined?

Major changes in fossils

Age of the Earth

~4.5 billion years old

Order of time divisions

Eras, periods, epochs

Fossil

any part, trace, or preserved remains of ancient life

Examples of fossils (8)

skeletons, shells, leaves, seeds, imprints, tracks, feces, and vomit

Majority of fossils

hard parts of extinct organisms

Paleontologist

scientist who studies fossils

How do fossils form?

body parts or impressions are buried in rock before they decompose

Are many ancient species in the fossil record?

No, most ancient species are not in the fossil record

Fossil Record

the growing collection of fossils that represents the preserved history of living things on earth

What type of rock are fossils formed in?

sedimentary rock

How does sediment bury the organism?

sediment is moved over the organism by lakes or seas

Amber preservation

hardened tree resin or sap that may trap and preserve small organisms

Examples of organisms preserved in amber

mosquitoes, scorpions, ants, moths, etc.

Does amber preserve the fine details of the organisms?

Yes 😁👍

Mummification

dead animals may dry up in hot and dry climates, possibly preserving their soft tissues

Carbonization

formed when a plant is pressed tightly between layers of slate rock, causing the plant's organic compounds to convert into a thin layer of carbon

Petrification

moving water over an organism dissolves its calcium and organic matter and replaces it with minerals, forming stone

Mold

formed when an organism makes an impression in soft mud, decays, and the mud turns into rock

Cast

formed when a mold is filled in by minerals, leaving a replica of the organism

Freezing

when an organism is trapped in a glacier, preserving soft tissues and last meal

Tar pits

an animal gets trapped in it, preserving its bones

La Brea Tar Pits

has provided the bones of many specimens

Why are predators usually trapped in tar pits?

they hear the cry of trapped prey, making them think they have the opportunity for an easy meal

Gastroliths

stomach stones that aid in digestion

Coprolites

fossilized feces

Which fossil types preserve the actual part of the organism rather than a resemblance?

Amber, Mummification, Tar Pits, and Freezing

Which fossil types preserve the soft parts of a creature?

Amber, Mummification, and Freezing

Relative dating

determines the age of fossils by comparing them to other fossils in different layers.

Law of Superposition

the oldest rock layers are in the lowest levels of the Earth's crust and the youngest are in the highest.

Radioactive/radiometric dating

process of dating rocks and fossils by measuring the amount of remaining radioactive isotopes it contains

Half-Life

the amount of time it takes for half of the radioactive elements in a sample to decay

Half-Life 2

a 2004 first-person shooter game developed and published by Valve Corporation, combining combat, puzzles, and storytelling

How is half-life used?

It is used to calculate the age of a specimen in years by multiplying the half-life.

Carbon-14 Dating

because of its shorter half-life and its abundance in organisms, it is used to accurately date organisms

Dendrochronology

dating trees by counting the spaces between dark rings

How do you calculate the year the tree started to grow?

(Year it started growing - age) + 1; A one is added to get the first year of the tree's life.

What do thin rings on a tree indicate?

sparse rainfall

How do you date back farther than a tree's lifetime?

by matching up the tree's rings with other trees to extend a timeline