Fossil Record

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?  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?

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

Fossils  What is a fossil?

Fossils  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 that’s 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.  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 that’s 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. (155 mya, 15 cm wingspan) (Baby Psittacosaurus in their nest, killed in Volcanic eruption 100+ mya)

Fossils  Preserved baby wooly mammoth, that’s its REAL body! Preserved in ice for a little over 10,000 years.  From such preserved bodies, we’ve sequenced all the mammoth’s mtDNA and most of its nuclear DNA. Scientists are also working on extracting viable gametes.  This, too, is a fossil even though it’s not a rock skeleton mold.  Preserved baby wooly mammoth, that’s its REAL body! Preserved in ice for a little over 10,000 years.  From such preserved bodies, we’ve sequenced all the mammoth’s mtDNA and most of its nuclear DNA. Scientists are also working on extracting viable gametes.  This, too, is a fossil even though it’s not a rock skeleton mold.

Fossils  Coprolites, or fossilized animal dung, indicate diet, behavior, infections, and more about the animal.  It also provides information about the ecosystem. Even if there’s 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:  Coprolites, or fossilized animal dung, indicate diet, behavior, infections, and more about the animal.  It also provides information about the ecosystem. Even if there’s 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:

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

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.  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.

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.   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. 

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.  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.

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.  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.

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. (We’ll 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.  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. (We’ll 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.

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.  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.

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.  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.

Using the Fossil Record  Remember the refrain?  More _____ = More ______ = More ______ Last Common Ancestor  Remember the refrain?  More _____ = More ______ = More ______ Last Common Ancestor

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!…  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!…

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

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

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

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

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  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

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.  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.

Using the Fossil Record  All of the above.  Archaeopteryx is a classic “intermediate form,” a creature with features definitive to two groups.  It’s not a true bird, or a true dinosaur. It has recent common ancestry with both.  All of the above.  Archaeopteryx is a classic “intermediate form,” a creature with features definitive to two groups.  It’s not a true bird, or a true dinosaur. It has recent common ancestry with both.

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

Essential Points About Fossil Formation  A fossil is a trace or remains of an organisms that’s 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.  A fossil is a trace or remains of an organisms that’s 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.

Essential Points About Life History  The “Tree of Life” is vast, with more extinct species than living ones. Most of the Earth’s history has been lifeless, or has only featured unicellular life. Humans are a very recent arrival.

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.  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.

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?  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?

Videos  windows-into-the-past-how-fossils- form-video.htm windows-into-the-past-how-fossils- form-video.htm  How fossils form   History of life  windows-into-the-past-how-fossils- form-video.htm windows-into-the-past-how-fossils- form-video.htm  How fossils form   History of life