Fossil Record

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Fossil Record
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Recap

• Who can explain to me
• What is a homologous structure?
• If two organisms share a homologous structure,
  what does that say about they relation to each
  other?
• What does that say about what their common
  ancestor looked like?
• What is a vestigial organ?
• What does a cladogram show?
• What is extinction?

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Objectives

• Have a general understanding of the timeline of
  life
• Be able to use fossil evidence to determine
  ancestry

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Fossils

• What is a fossil?

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Fossils
(155 mya, 15 cm wingspan)

• What is a fossil? A fossil is any trace or
  remains of an organism, preserved by natural
  processes.
• Fossilized skeletons are the obvious example, but
  thats not all that fossils are limited to.
• Fossils include fossilized droppings, tracks,
  eggs, nests, tracks, body imprints, and even
  whole bodies preserved in ice, tar, or amber.

(Baby Psittacosaurus in their nest, killed in
Volcanic eruption 100 mya)
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Fossils

• Preserved baby wooly mammoth, thats its REAL
  body! Preserved in ice for a little over 10,000
  years.
• From such preserved bodies, weve sequenced all
  the mammoths mtDNA and most of its nuclear DNA.
  Scientists are also working on extracting viable
  gametes.
• This, too, is a fossil even though its not a
  rock skeleton mold.

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Fossils

• Coprolites, or fossilized animal dung, indicate
  diet, behavior, infections, and more about the
  animal.
• It also provides information about the ecosystem.
  Even if theres no independent imprint of a
  plant, it can still be recorded in the droppings
  of local herbivores, for instance.
• T-Rex coprolite 50 cm long

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Fossils

• The oldest insect preserved in amber comes from
  146 million years ago. Amber has also preserved
  bacteria, archaea, plants, and protists.

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Fossils

• There are nearly 100 different ways to date a
  fossil.
• Carbon-14 dating, potassium-argon dating,
  uranium-lead dating, biostratigraphy
• Some methods are more chemistry-based, others are
  more exclusive to geologists
• Scientists use many of them on each fossil to be
  confident of their results.

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History of Life

• The Tree of Life is vast, beginning 3.8 billion
  years ago and with more extinct species than
  living ones. Humans have only occupied a small
  fraction of it. Observe
• Earth is 4.6 billion years old.
• The first thing that met all the characteristics
  of life developed 3.8 billion years ago.
• The first multicellular organism developed 1
  billion years ago.
• The first animal developed 600 million years ago.
• The first species in the genus Homo developed 2.5
  million years ago.
• The first Homo sapiens developed 200,000 years
  ago.
• http//www.wellcometreeoflife.org/

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Using the Fossil Record

• How can the fossil record be used with respect to
  evolutionary history?
• The broad trend Fossils show that the form and
  structure of organisms have changed over time.

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Using the Fossil Record

• How can the fossil record be used with respect to
  evolutionary history?
• The broad trend Fossils show that the form and
  structure of organisms have changed over time.

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Using the Fossil Record

• Fossils also provide information and the where
  and when.
• Dating the fossil tells you the when.
• The location of the fossil tells you about the
  range. (Well do a lab of this soon.)
• Geologists love us evolutionary biologists, our
  fossils have the added benefit of giving them
  more data on tectonic plate shifts.

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Using the Fossil Record

• You find two fossils in the same layer of rock.
  One is a plant, the other an insect. From this,
  you can conclude
• A. The insect ate the plant
• B. The insect laid its eggs on the plant.
• C. They lived at the same time.
• D. They lived at different times.

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Using the Fossil Record

• You find two fossils in the same layer of rock.
  One is a plant, the other an insect. From this,
  you can conclude
• C. They lived at the same time.
• Your conclusions about their lives will depend on
  more than just finding them in the same layer.

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Using the Fossil Record

• Remember the refrain?
• More _____ More ______ More ______ Last
  Common Ancestor

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Using the Fossil Record

• Remember the refrain?
• More SIMILAR More RELATED More RECENT Last
  Common Ancestor
• Fossils are used to determine ancestry by
  comparing them with living organisms and other
  fossils.
• Fossils show homologous and vestigial structures
  just like living creatures do.
• For example!

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• This fossil is dated to 145 mya. What are your
  observations?

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• Do you notice any homologous structures that this
  species shares with birds?

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Using the Fossil Record

• Do you notice any homologous structures that this
  species shares with birds?
• Feathers on wings, tail, body
• Fused clavicles
• Opposable big toe
• Many more

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• Do you notice any homologous structures that this
  species shares with dinosaurs?

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Using the Fossil Record

• Do you notice any homologous structures that this
  species shares with dinosaurs?
• Jaws with pointy teeth
• Long bony tail
• Three claws on each arm/wing
• Killing claws on toes
• Many more

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Using the Fossil Record

• This species is called Archaeopteryx. Which of
  the following are appropriate conclusions we can
  draw?
• A. Archaeopteryx shares a common ancestor with
  birds.
• B. Archaeopteryx shares a common ancestor with
  dinosaurs.
• C. The common ancestor for Archaeopteryx and
  birds had feather-like structures.
• D. The common ancestor for Archaeopteryx and
  dinosaurs had a bony tail.
• E. Archaeopteryx is more closely related to birds
  than to humans.

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Using the Fossil Record

• All of the above.
• Archaeopteryx is a classic intermediate form, a
  creature with features definitive to two groups.
• Its not a true bird, or a true dinosaur. It has
  recent common ancestry with both.

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Problems

• Five problems incoming. A sticker if you get all
  five correct.

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Essential Points About Fossil Formation

• A fossil is a trace or remains of an organisms
  thats been preserved by natural processes.
• These can include fossilized bones, imprints,
  tracks, amber or ice-preserved bodies, etc.
• Any organism can leave a fossil, though this
  happens more easily to some organisms than to
  others.
• We have fossils of everything from bacteria to
  plants to many kinds of animals
• There are more nearly a hundred different ways to
  date a fossil. Scientists use many of them on
  each fossil to be confident of their results.

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Essential Points About Life History

• The Tree of Life is vast, with more extinct
  species than living ones. Most of the Earths
  history has been lifeless, or has only featured
  unicellular life. Humans are a very recent
  arrival.

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Essential Points About Fossil Data

• Fossils show that the form and structure of
  organisms have changed over time.
• They also provide information about where when.
  Fossils found in the same layer of rock come
  from organisms that existed in the same time
  period. Deeper layers of rock come from further
  back in history.
• Fossils are used to determine ancestry by
  comparing them with living organisms and other
  fossils.
• Fossils show homologous and vestigial structures
  just like living creatures do.

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Extinction!

• What is an extinction?
• If species are all constantly evolving all the
  time according to the pressures of their current
  environments, why do extinctions happen?

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Videos

• http//videos.howstuffworks.com/hsw/12698-windows-
  into-the-past-how-fossils-form-video.htm
• How fossils form
• http//www.wellcometreeoflife.org/
• History of life