1 Flashcards
What are direct evidence of organisms that lived in the past?
Fossils
Coprolite?
Fossilized feces
How do fossils form? 7•
•predators and scavengers
•bacterial decay
•dissolution in water
•physical disturbance (wave action, wind)
Special conditions:
•Rapid burial
•protection from physical disturbance
•Anaerobic environments
•No bacteria
Since brutal is key, a lot of fossils are found in?
Sedimentary rock.
Types of preservation? 4•
•Original remains: skeletal or other body elements
•Preminerlization: minerals deposited within tiny holes within bones or wood and overtime replace the original organism.
•trace fossils
•Impression fossils: only carbonaceous film
What is the most important type of fossilized preservation that can greatly inform morphology?
Original remains
Lagerstatten?
Lager = storage, satte = place
Cambrian explosion?
The period of time where such a diversity of animals exploded about 541 million years ago.
Steno’s four principle on relative dating?
•Superposition
•Original horizontality
•Lateral continuity
•Cross-cutting
Superposition?
Layers of rocks differ in age. Oldest at the bottom and youngest at the top.
Original Horizontality?
Layers are first deposited horizontally and then may deformed later.
Lateral continuity?
All rock layers are laterally continuous but may be broken up eventually, such as erosion.
Cross-cutting later?
Intrusions are always younger than any of other layers they are cross cutting.
Index fossils?
Fossils that are distinct to a particular rock layer and are also geographically widespread to help identify layers in different locations.
Conditions for index fossils? 2•
•have lived for a short time
•are geographically widespread
Trilobites?
Extinct arthropods, crustaceans, and insects that are all marine and really widespread.
William Smith discovered what?
Found many of the same fossil sequences in different areas around the UK.
Some geological timescale layers are named after?
Features, some as places
Stratigraphic mapping during William Smith’s time lead to?
The geological timescale
The geological time scale (GTS) only contains the eras and periods within the?
Phanerozoic Eon (visible life).
What period did the GTS start?
Cambrian (where multicellular animals appear)
When did life first evolve?
3.7 billion years ago
Relative dates?
Comparing which is older between two rock laters.
Absolute dates?
Finding precise dates of a rock layer
Absolute dating is based on?
Radiometric dating
Absolute data can only be done in?
Igneous rocks because 100% of the parent isotopes are present at day 1
The intrusion in cross-cutting is always older/younger than the layers?
Younger
