Fossils and Geologic Time Flash Cards
What are the five types of fossils?
Original remains, carbon film, mold, cast, and trace.
What is original remains?
These are fossils that contain the original parts of the actual organism. Ex, bones, teeth, and entire body.
What is carbon film?
All living things are made of carbon. A carbon film is the film of carbon left on a rock by a decaying organism and is preserved as a fossil.
What is mold?
Fossil that forms when an organism decays or dissolves and leaves a cavity in the rock.
What is cast?
Fossil that forms when a mold fills with sediment and then hardens into rock.
What is trace?
Preserved footprints, trails, burrows, or any marks that tell about how things lived.
What is fossil indexing?
- Fossils can be used to date layers of sedimentary rocks.
* These are remains of species that lived for a short time and were numerous, and found in many places.
What is the geologic time scale?
- The division of Earth’s history into time periods based on the type of life forms that existed.
- The appearance or disappearance of organisms throughout history marks the important events in geologic time.
What is the first time period?
PRECAMBRIAN TIME
Time: 4.5 billion years ago-544 million years ago
What is a fossil? What type of rock is it mostly found in?
A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth’s crust; mostly found in sedimentary rocks.
What were the earth and life forms in the Precambrian time?
Earth: *Most things lived in the oceans *Land covered with volcanoes Life: *First forms of bacteria *Jelly fish, worms, and other soft-bodied animals
What led to the end of the Precambrian time?
The appearance of shelled organisms.
What was the second time period?
PALEOZOIC ERA
Time: 544 million years ago-248 million years ago
What were the earth and life forms of the Paleozoic era?
Earth:
*Warm, shallow seas covered much of Earth
*Several mountain ranges began to form as plates collided
Life:
*Shelled organisms, especially trilobites
*Fish-like organisms without jaws
*Early plants
*Toward the end of the era, amphibians and reptiles appeared
What led to the end of the Paleozoic era?
- Most of the ocean and land animals became extinct
- Perhaps, as Pangaea formed, changes to the ocean and land caused species to die.
- Another theory is that massive volcanic eruption led to the death of these species
What was the third time period?
MESOZOIC ERA
Time: 248 million years ago-65 million years ago
What were the earth and life forms in the Mesozoic era?
Earth: *Pangaea begins to break up *The climate became very dry Life: *Reptiles survived mass extinction of Paleozoic era *Age of the dinosaurs *Early birds, fish with bones, and small mammals *More modern plants
What led to the end of the Mesozoic era?
- Most land and ocean species became extinct (dinosaurs disappeared)
- Possibly, a huge asteroid hit the Earth
- Impact put huge cloud of dust in the atmosphere, blocking out the sunlight. Without sunlight, plants dies as well as the animals that fed in plants
What is the current era?
CENOZOIC ERA
Time: 65 million years ago-present time
What were are the earth and life forms of the Cenozoic era?
Earth:
*Mountain ranges in North and South America formed
*Modern grasslands
*The climate became cooler (Ice Age occurred)
Life:
*During Ice Age: mammoths, saber tooth tigers, etc. (became extinct after Ice Age)
*Grazing animals arrived: horses, rhinos, etc.
*Modern mammals: birds, reptiles, fish, and amphibians
*Modern plants
