fossil Flashcards
Fossils
The preserved remains, imprints, traces or evidence of ancient, prehistoric living things organisms.
Prehistoric
before history was written.
What do fossils tell us
Tells when, where and how organisms lived.
Petrified wood
a special fossilized wood; the result of a tree or tree-like plants having completely transitioned to stone by the process of permineralization.
What cant fossils tells us?
While fossils reveal what ancient living things looked like, they keep us guessing about their color, sounds, and most of their behavior.
Are fossils common
No, they are very rare
What is a fossil record like
a big jigsaw puzzle, with most of the pieces missing.
Where are most fossils found
Sedimentary rocks
What exposes fossils at Earth’s surface
Weathering and erosion
What happens when minerals replace the organic matter or fill the empty pore spaces of an organism?
Minerals replace the organic matter or fill the empty pore spaces, leading to fossilization.
What do fossil clues provide
What living things existed in the past, How organisms changed over time, and what ecosystems and environments were like
What can you conclude about past in places fish fossils are found
The area was once covered by water, such as an ocean, lake, or river, where fish lived before being fossilized
Catastrophism
Idea that conditions and organisms change in quick violent events
Catastrophism example
volcanic eruptions, and widespread flooding
Did scientists agree with this idea?
Scientists disagreed with this idea bec Earth’s history is full of violent events and they believed that most changes on Earth happen slowly and gradually over time, not just through sudden, violent events
Uniformitarianism
\
Geologic processes that occur today are similar to those that have occurred in the past.
present is key to the past
* Earth has 2 types of change: Slow, everyday process and violent, unsual events.
example of Uniformitarianism
In the 1700’s Hutton observed how the landscape on his farm gradually changed over the years, concluding this could also shape Earth’s surface in a steady, uniform manner.
how does Uniformitarianism happen
though erosion caused by streams could weather down mountains
Why study fossils
helps determine the absolute age and relative ages of rocks, provides clues to past geologic events, climates, and evolution to living things, and it indicates and areas acient environmental conditions and climates
7 best conditions for fossils to form
Quick burial in moist sediments
quick burial in volcanic ash
Hard body or plant parts
consistent temapatures
lots of minerals in the ground and water
very fine sediments
calm conditions
Why is the brurial in moist sediments a good condition for fossils to form
prevents scavengers and bactiria from destroying
Why is lots of minerals in ground water a good condition for fossils to form
bc the minerals slowly replace the body
Types of fossils
Body fossil and trace fossils
Body fossil
The remains of part (or all) of an actual organism.
5 types of Body Fossil preservation
Permineralized remains
Carbon Films
Coals
Molds and Casts
Original remains
Trace fossil
traces or marks left behind by an organism. They show an organism was there, but are not the actual organism itself like trails, tracks, and burrows
Mineral replacement
When minerals fill small holes in hard parts like bone, teeth & shells
Permineralized remains also known as
petrified fossils
In some permineralized remains
Bones have small holes that are usually filled with blood, cells or nerves. When the original dies, soft tissue decays leaving holes for minerals to fill.
What type of fossilization process is described when water dissolves a buried fossil, fills the space with minerals, and replaces the remains with rock?
This process is called permineralization or replacement fossilization, where minerals in groundwater replace the original organic material, turning it into stone. In some cases, the fossil may even retain traces of the original genetic material.
Carbon Films
a type of fossil that forms when an organism is pressed between layers of mud or clay. Over time, heat and pressure remove liquids and gases from the organism, leaving behind a thin layer of carbon that preserves its shape and details. This process often occurs with plants, leaves, fish, and other soft-bodied organisms.
Coal
Plant matter is buried and carbonized, forming coal. The plant’s structure is usually lost, revealing little about it.
Mold
Rock has pore space & allows water to flow through decaying the organism & leaving behind a cavity in the shape of the organism
Cast
rich water flows through mold & fills cavity producing a copy of the organism
Amber
sticky tree resin
Soft parts in original remains can be preserved in
Amber, ice, tar
What can trace fossils tells us
Can tell size, weight, age, social behavior (how the animal lived.)
Trails and burrows
Tunnels have been left behind by
How can fossils determine past climates
Organisms that are limited to certain habitats can be found in completely different habitats.
How do you explain crinoid (animals that live in shallow sea) found in rocks by the desert today? .
This proves that when the crinoids were alive, shallow sea covered western and Central North America
how to figure out relative age
if the rocks haven’t been faulted or turned upside down.
In cases where rock layers have been disturbed you might have to look for fossils and other clues to date the rocks.
Rocks from different areas may be correlated if
if they are part of the same layer.
Relative age
its age in comparison to the ages of other things. It doesn’t tell you anything about the age of the rock layers in actual years, but you can conclude if it’s younger or older.
Geologists determine the relative ages of rocks and other structures by
examining their places in a sequence
Principle of Superposition
The Principle of Superposition states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom, and the layers become progressively younger toward the top. However, mountain-building forces can sometimes disturb this order.
Principle of Original Horizontality
The Principle of Original Horizontality states that most rock-forming sediments are originally deposited in horizontal layers. However, these layers can later be tilted or folded due to geological forces.
lateral Continuity
when the sediments are deposited in large, continuous sheets in all lateral directions, but then out / meet a barrier. Ex) River may erode but the placements do not change
Inclusions
When a piece of an older rock becomes part of a new rock
*If one rock contains pieces of another rock, the rock containing the pieces is younger than the pieces.
Cross-Cutting Relationships
*When forces within Earth cause rock formations to break/ fracture
*When rocks move along a fracture line this is called a fault.
*If one geologic feature cuts across another feature, the feature that it cuts across is older.
Unconformities
surface where rock has eroded away & younger rocks have been deposited, producing a break or gap in the rock record of a few hundred to billions of years
When rocks are exposed, wind & rain weather & erode them causing gaps in the rock record.
Disconformity
Sedimentary rocks form and then are eroded; new, younger sedimentary rocks are laid down on top of eroded surface
* Are gaps in the rock record.
Angular Unconformity
*Sedimentary rocks form and then
are tilted and eroded; new sedimentary rocks are laid down on top
Nonconformity
*Younger sedimentary rocks are deposited on top of igneous or metamorphic rock layers that may be eroded
3 possible cause of unconformities
Uplift, weathering and erosion, subsidence (Sinking of land)
Correlation/ Connection
matching rocks & fossils from separate areas may be related if they are part of the same layer.
Historical records can be determined.
Sometimes relative dating is not enough, other testing is needed.
index fossils- What is an index fossil and how are they used?
*remains of species that existed on earth for relatively short periods of time were abundant and widespread geographically.
*Organisms that became index fossils lived only during specific intervals of geographic times, geologists can estimate the ages of rock layers based on the particular index fossils they contain.
Radioactive decay
he process where unstable isotopes break down into other isotopes and particles. This decay is measured in half-lives, which is the time it takes for half of a given isotope to decay.
radiometric dating
by measuring the ratio of parent isotope to daughter product, one can determine the absolute age of a rock.
Relative dating
uses geologic sequence of events by comparing rock layers, but cannot tell how long ago the events occurred.
absolute dating
uses radioactive decay
the actual age in years of a rock or other objects
geologists determine absolute ages by using properties of the atoms that make up materials.
what are the 4 major subdivisions of geologic time
eon, era, epoch, period
eon
the largest division; divided into eras
era
2nd largest; includes two or more periods
period
3rd largest; unit into which includes more epochs
epoch
4th largest, the subdivision of a period
Scientists placed Earth’s rocks in order by relative age to create
the geologic column
Radioactive dating helped us determine
the absolute date of the divisions in the geologic scale
Precambrian
the name given to the earliest span of time in Earth history. Makes up nearly 90% of Earth’s history.
Rare fossils of multicellular life forms are from soft-bodied organisms different from today.
Hadean eon
rocks from meteorites & moon
Archean Eon
– earliest rocks on earth form
Proterozoic Eon–
organisms with well developed cells
Phanerozoic Eon–
means “visible life”
what eons are in the precambrian time
Hadean, archean, and proterizoic
4 eras
Precambrian,paleozoic, mesosoic, and cenozoic
Paleozoic Includes:
*Cambrian – being the first period is important; “Cambrian
Explosion”; 1st trilobites
*Ordovician – 1st Vertebrates
*Silurian – 1st Land Plants
*Devonian – Age of Fish (when it flourished)
*Mississippian – Winged insects
*Pennsylvanian – First reptiles
*Permian – Age of Amphibians
(when it flourished)
What is the term used that explains the ending of Precambrian Time,
Paleozoic Era & Mesozoic Era?
Mass extinction.
when and what caused the Precambrian Time mass extinction
4.5 billion to 544 mya
Glaciation events (Ice ages)
when and what caused the paleozoic era mass extinction
Volcanic activity
climate changes
lowering of sea levels
when and what caused the mesozoic era mass extinction
Asteroids, comments, and meteor collided with earth
when and what caused the cenozoic era mass extinction
There is none because we are still living
What animals lived during the Mesozoic Era?
Dinosaurs, birds, small mammals, and reptiles.
Did humans live during the Mesozoic Era? If not, in what era did they appear?
No, they appeared in the Cenozoic Era.
What types of fossils were found from Precambrian Time?
Trace fossils; Rare fossils of multicellular life forms are from soft-bodied organisms different from today.
Would Precambrian Time have a lot of fossils? Why or why not?
No, because soft bodied animals do not leave a lot of fossils
Early Paleozoic is known as the Age of
Invertebrates or trilobites
Middle paleozoic is known ad the age of
fish
Late Paleozoic is known as the age of
amphibians
Mesozoic is known as the Age of
Dinosaurs or Reptiles.
Cenozoic is known as the Age of
Mammals.
Determining relative age is easy, as long as the rock layers are horizontal. How can you determine the age of a rock if the rock layers are turned? What can cause the rock layers to no longer be horizontal?
Looking at fossils, earthquakes (thrust faults), mountain building.
unconformities and how r they formed
*Rock sequences are incomplete\
*layers are missing
*Develop when agents of erosion such as running water or glaciers remove rock layers by washing or scraping them away.
How do scientists match up rock layers?
*rock layers are exposed only where rivers have cut through overlying layers of rock and sediment.
*Same type of fossils were found in layers- good indication was one continuous deposit
What is absolute age? How do scientists determine the absolute age of rocks?
*Age in years of a rock or other object
*You can determine the absolute age by using radioactive decay and properties of atoms that make up materials - some isotopes are unstable and break down into other isotopes and particles - a lot of energy is given off during this process
What are some slow, everyday processes and what are some violent, unusual events?
Slow: Plate movement, glaciers, ice age, changes in atmosphere/water
Violent: Meteor, earthquakes, volcano, extreme water.
What eon, era, period, and epoch are we currently living in?
Phanerozoic Eon, Cenozoic era, Quaternary period, Holocene Epoch
What happend in the early paleozoic?
The Cambrian Explosion = “Age of Invertebrates”,
lived in the ocean and had no backbones.
Ended with mass extinction.
Middle Paleozoic “Age of Fish”
*Animals with backbones evolved.
*On land, cockroaches, dragonflies & insects evolved.
*Earth’s 1st plants appeared, they were small & lived in water.
*Continents collided. Appalachian mountains formed.
*Ended with mass extinction.
Late Paleozoic
“Age of the Amphibians”
*Amphibians adapted to land-had lungs, could breath air, thick skin slowed moisture loss.
*Strong limbs let them move around on land, but they did go back to the water to lay eggs.
*Reptiles evolved. Did not need water for reproduction. It’s eggs have rough, leathery shells that protect them from drying out.
*Coal swamps during the Carboniferous & Permian Periods became our major source of coal we use today.
*Continental collisions formed a giant supercontinent called Pangaea. Coal dried up, climate became cooler.
*Carboniferous period is the Mississippian Period & Pennsylvanian Periods combined.
Permian mass extinction
Large mass extinction.
*95% of marine life & 70% of all life on land became extinct.
*Maybe Pangaea decreased the amount of space where marine mammals could live.
*Ocean currents made the center of Pangaea drier.
*A large meteorite or a massive volcanic eruption could’ve impacted climate change-reducing sunlight, reducing temperature and collapsing the food web.
Mesozoic Includes:
Triassic – First Dinosaurs/Small mammals
Jurassic – First Birds/Flowering Plants
angiosperms-plants with flowers & seeds enclosed in their fruit
gymnosperms- plants with cones, no flowers or fruits; have naked, no protective covering seeds on the surface of their leaves
warmer then paleozoic
Dinosaurs & reptiles dominated during the Mesozoic Era. Mammals evolved & remained small in size.
*But other animals adapted to environments of lush tropical forests & warm ocean waters.
Most of the time there were no ice caps & no glaciers so the oceans had more water.
- Narrow channels grew larger as the continents moved apart. The channels became oceans, Atlantic ocean for example.
*Sea level rose, evaporated & massive salt deposits were left behind.
*The Rocky Mountain formed during this time.
Cretaceous Mass Extinction
Was due to large meteorite or volcanic eruption.
*This added extra dust, no sunlight, killing plants & animals.
*Dinosaurs & large Mesozoic species could not adapt & became extinct.
Cenozoic Era Includes:
Tertiary – Mammals Thrive
Quaternary – Age of Man/Technology
Pleistocene Epoch-
the 1st epoch of the Quaternary period.
Ice Age: when a large proportion of Earth’s surface is covered by glaciers
Mountain Building:
*India crashed into Asia forming the Himalayas-the highest mountain on Earth today.
*Africa pushed into Europe-forming the Alps.
*On the west coast of North America -the Rocky Mountains continue to grow.
The Cascade & the Sierra Nevadas-formed on the West coast.
*On the east coast the Appalachian Mountains continue to erode.
Cennozoic life
large mega-mammals; woolly mammoth, giant sloths, saber-toothed cats- lived under the cooler climate Pliocene and Pleistocene
*Humans appeared.
