fossils

Why are fossils important?

• Reconstructing Environments

• ID-ing animals/plants

• tracing evolution.

What are the three types of fossils?

Plants, Insects, vertebrates

What percent of known fossils are marine animals?

90% of all fossils are marine animals

How old must remains be to be considered a fossil?

Depends-

• Some say older than historic time

• others say it must date back from before start of Epoch known as recent (or at least 11,000 years ago)

• if animals are extinct, they are considered fossils no matter the age.

What is a subfossil?

A fossil not yet mineralized yet (if they are recent remains)

What parts of animals and plants are normally preserved?

The hard parts of them. For instance, on animals, these "hard parts" may be shells, bone, or teeth.

What are molds and how are they formed?

Hard parts of a fossil might dissolve, sediment hardens, leaving a cavity in a rock called this.

What's it called when the outside of a shell eaves an imprint?

External mold.

What's it called when the inside of a shell leaves an imprint?

Internal mold

What are Steinkerns

if interior shell fills with mud, and hardens, and the matrix surrounding it is taken away, the internal mold is called this.

In what organisms are Steinkerns most commonly formed?

Snails.

Bivalves/Brachiopods can be preserved this way too.

What is a cast?

If the cavity left by a shell has filled with minerals, it is called this.

What minerals normally fill a cast?

Calcite, silica, and pyrite.

What are petrifactions?

When original material is replaced by minerals which gradually seep into the fossil thru surrounding matrix.

What is often preserved by petrifactions?

Wood and bone

What are films?

When leaves (and occasionally animals) leave a carbon film on rock surfaces.

What color carbon is most stable to record exact shape of a leaf (with film fossils)?

Brown/black carbon

Are animals preserved by "Films"?

Sometimes, but when it is, the material remaining may not be carbon. The leaves/animals preserved by distillations leaves impression on rock.

What are trace fossils?

Not part of an animal, but a trace of animal activity.

What are examples of animal activity trace fossils?

• record of animal movement (tracks)

-feeding activity

• burrows

-feces (poop :O)

When feces (coprolite) fossils are left, what is useful about it?

It may have partially digested food remains, which can give you a glimpse at animals ecology.

What basic units is geologic time broken up into?

Eons, eras, periods, and epochs.

What are geologic time units characterized by?

• Different environmental conditions

• specific kinds of life that flourished there

How are fossils found in rock normally formed?

Formed from sand, silt, or other fine sediments that settled from bottom of water body, then hardened into stone.

Fill in the blank.

Before the beginning of this century, scientists could only determine the _ ages of fossils/rock.

Relative

What are layers of rock separated by?

Erosional surfaces

Fill in the blank.

Rocks that are laid down first are than rocks laid down above them.

older

When was the first success time someone predicted absolute geologic time?

1896.

What discovery lead to absolute dating?

Radioactive decay.

Explain what radioactive decay is.

When elements loose particles from atomic nuclei, and give off electromagnetic radiation in the process.

How does radiometric dating work?

Since rock crystals have proportion of different elements when they form, it's possible to measure the amount of new isotope since the formation, and the age can be determined b/c the rate of decay for rocks is known.

What is the possible range of error for radiometric dating?

2-10 million years of error

What were the two eons?

Precambrian and Phanerozoic eons

When did the precambrian eon start and end?

• Began with the formation of earth

• ended when fossils became abundant

when did the Phanerozoic eon start and end?

• began with close of precambrian

• hasn't ended, and continues today

What are the three eras of the Phanerozoic eon?

Paleozoic, mesozoic, and cenozoic.

What are eons divided into?

Eras.

What are eras divided into?

Periods.

What periods is the paleozoic era divided into?

Cambrian, ordovician, silurian, Devonian, Mississippian, Pennsylvanian, and permian periods.

What periods is the mesozoic era divided into?

Triassic, jurassic, and Cretaceous periods.

What periods is the cenozoic era divided into?

Tertiary and quaternary.

How are the paleozoic/mesozoic era's period's epoch's divided into?

Early, middle, and late.

What epochs are the tertiary period divided into?

Paleocene, Eocene, Oligocene, Miocene, and pliocene.

What epochs are the quaternary period divided into?

Pleistocene and the Recent (holocene).

What are Cambrian rocks called?

the Cambrian System.

How fast are tectonics moving a year?

1-6 cm a year.

How do plate tectonics help explain the history of life?

-W/ Plate tectonics, paleontologists could account for moving organisms without land bridges.

• it explains why rocks of the same located close to one another have different fossils .

How are changes in sea level important to marine/terrestrial life?

Most marine species are in shallow seas bordering continents.

Is sea level very constant?

Nah

What are the three factors determining how much continents are covered by seas at a time?

Volume of ocean basins, volume of water in ocean basins, and height of the continents.

What is an important factor when thinking about the volume of ocean basins?

The height of mid ocean ridges

Fill in the blank.

If ridges are _ (high/low?), the ocean holds less water.

High.

How is the volume of water in ocean basins affected by continental glaciation?

It has huge withdrawals of water.

What are the short/long term affects if the sea level fell 500' now?

• Edges of continental shelves would be exposed.

• short term- mountain ranges rise and eroded down to sea level in a few million years

-long term- processes of plate tectonics add light crust material to continent, which becomes higher thru time.

How many mass extinctions were there during the Phanerozoic Eon?

6 times

What percent of fossil families extinct during the mass extinctions?

25-50 percent fossil families extinct in a short time.

When did these 6 mass extinctions of the Phanerozoic eon take place?

Close of the..

-Cambrian, ordovician, Devonian, permian, triassic, and Cretaceous periods.

If there is a 50% reduction in families of fossils, what is the percent of reduction for species.

90% ( D: )

Was the phanerozoic or precambrian eon bigger?

Precambrian.

The largest division in Earth's history is the ____ eon.

Precambrian.

The precambrian eon is ____% of earth's total time (of 4 billion years)

88%

What is the oldest rock dated?

3.8 billion years ago.

How long is the Phanerozoic eon?

less than 600 million years.

When was the first evidence of life in rocks?

3.4billion years ago.

In what kind of rock was the first evidence of life found?

Chert and Silicon dioxide, in the formation called "fig tree" .

Describe the oldest first fossils found.

• Found in Chert and Silicon dioxide.

• spherical, cylindrical, all like varieties of bacteria

• procaryote

• fed by absorbing nutrients thru cell walls

-

What is proof there was no oxygen during early precambrian?

Because there was no oxidization of compounds.

Where did the first organisms get nutrients?

From nutrients dissolved in water.

After the supply of nutrients in the water went away, what happened? How did organisms get energy?

They started making their own food- By photosynthesizing!

What are stromatolites?

Mounds of layered rock formed in shallow water, when algae filaments make a layer binding sediment together, and this pattern continues.

When were the first certain photosynthesizes, and what were they called?

3 billion years ago.

They were called Blue Green Algae

How old are the first Eukaryotes?

1.4 billion years old.

where were the first Eukaryote fossils found?

Beck Spring area, California.