Evolution and Fossils. Fossils: Fossil: the preserved or mineralized remain or imprint of an...
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Transcript of Evolution and Fossils. Fossils: Fossil: the preserved or mineralized remain or imprint of an...
![Page 1: Evolution and Fossils. Fossils: Fossil: the preserved or mineralized remain or imprint of an organism that lived long ago.](https://reader030.fdocuments.net/reader030/viewer/2022033102/56649ee05503460f94bf0033/html5/thumbnails/1.jpg)
Evolution and Fossils
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Fossils:
• Fossil: the preserved or mineralized remain or imprint of an organism that lived long ago.
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Age of rocks can tell us the age of fossils
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Fossils are remains of ancient life
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3 major points on evolution through the
use of the fossil record:•Earth is about 4.5 billion years old
•Organisms have inhabited Earth for most of its history
•All organisms living today evolved from earlier, simpler life forms
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• Most fossils form when organisms and traces of organism are rapidly buried in fine sediments deposited by water, wind or volcanic eruptions
• Paleontologists: scientists who studies fossils.
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Becoming A Fossil• Scientists have
described about 250,000 different fossil species– Yet that is a small fraction of
those that lived in the past!
• Evolution can be seen in the fossil record.– Fossilized species found in
older rocks are different from those found in newer rocks
•
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Fossil formation• The oldest fossils are
remains of marine organisms that populated the planet's oceans.
• When they died, the plants and animals were buried by mud, sand, or silt on the sea floor.
• Land animals and plants usually decomposed or were eaten, and mainly the hard parts -- teeth, bones, shells, or wood -- were preserved.
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Fossils can be formed in several ways
• Buried bone and shell contain tiny air spaces into which water can seep, depositing minerals.
• Reinforced by these mineral deposits, bone and shell can survive for millions of years.
• Even if the bone or shell dissolves, the mineral deposits in the shape of the body structure remain.
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Quick Recap:
• Arrange fossils in sequence from oldest to youngest to see patterns of evolution
• Fossils are classified according to the way they are found
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Fossils are found in layers of rock
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• The oldest rock layers (and therefore the oldest fossils) are always on the bottom
• The youngest are on top.
• This is referred to as superposition (super = above)
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Oldest to the bottom:
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Becoming a Fossil
http://www.ucmp.berkeley.edu/education/explorations/tours/fossil/9to12/intro.html
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Organisms die and are buried by sediment
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• Their weight causes the lower layers to harden into sedimentary rock, trapping the organism or trace inside.
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Not all fossils are formed by sediment
Found in Tar Pit
Found in Amber
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• http://www.pbs.org/wgbh/evolution/library/04/3/l_043_01.html
• Casts: a mold of an organism is created and then filled by minerals making an exact copy
• Molds: AN organism decays leaving an empty space in the rock that is the exact shape of the organism
• Imprints: Thin objects such as leaves or feathers fall into mud and then mud hardens
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• Trace Fossils: Evidence of animal activity (footprints, trails, etc.)
• Petrified fossils: the hard part of the organism is replaced with minerals and the minerals harden making an exact stone copy.
• Amber-preserved: Rare, but when found whole organism is preserved.
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• Interpretation of fossils poses another set of challenges
• Their age can only be estimated by radiometric dating of rocks they were found near or within
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Relative dating:
•fossils on the bottom are the oldest, and the ones on the top are the youngest
– Only tells if one fossil is older than another
Relative dating:
•fossils on the bottom are the oldest, and the ones on the top are the youngest
– Only tells if one fossil is older than another
Radiometeric dating:
•radioactive isotopes are used to determine age of fossil
Radiometeric dating:
•radioactive isotopes are used to determine age of fossil
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Fossils can show us how ecosystems change• Nevada’s Silver Peak Mountain Range
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Fossil of a marine animal found in the rocks of the desert
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• Archaeocyathids were a group of sponges that lived about 500 million years ago, and are now extinct.
• They built huge reefs (similar to coral reefs we see today) and were extremely important members of their ecosystems
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What could explain finding fossils of sponges in the Nevada desert?