PaleontologyPaleontology

OnlineHS Biology: EvolutionOnlineHS Biology: Evolution

• What is stratigraphy?

• Write a statement about the age of the various layers (and fossils that may be found in those layers) you observe in the strata model at right.

PaleontologyPaleontology

Paleontology Essays DebriefPaleontology Essays Debrief

• Fossils can be formed in many ways:– Mineral replacement

– Cooled ash/lava encasing an organism

– Arctic Ice (mammoth)

– Tree Sap (insects)

– Footprints (“trace fossils”)

• Bones are a typically fossilized tissue.

PangeaPangea

• The theory of Pangea/plate tectonics suggests that changes in land connections allowed some living organisms to move to new areas.

• This changed the “environment” in which certain things lived.

PangeaPangea

• How do you think the movement of plates affected GROUPS of organisms living in Earth’s past?

How Old?How Old?

• There are a few ways to determine age of fossils:

– Indirectly, based on where it was found (“relative” dating)… “younger vs. older”

– Directly, based on the fossil itself (“absolute” dating) using elements that make up the fossil

• Chemistry!– Radioactive Isotopes: Elements

that undergo steady decay and can be useful for determining the age of objects.

• Example: C-14

Fossils in layersFossils in layers

• Observe the following diagram that represents Earth’s layers (“strata”).

• What can you infer about the fossils that appear in each of those layers?

• Radioactive Isotope: Elements that undergo steady decay and can be useful for determining the age of objects.

– Examples: C-14 • Half-Life: the rate at which

radioactive isotopes decay (which varies for each element/ substance)

• One half-life is the amount of time it takes for half of the atoms to change into something else.

• Scientists can apply the concept of half life and calculate approximate age by looking at how much “stuff” is left in the fossil.

TermsTerms

How Do You Determine Age?How Do You Determine Age?

• Potassium-argon dating. • A method of determining the time of origin of

igneous rocks and sediments--and thereby the fossils found within them--by measuring the amount of decay of potassium-40, a radioactive isotope of the element potassium, into the stable isotope argon-40, one of the rare gases.

• The half-life of potassium-40, which is the time it will take one half of any quantity of it to decay into potassium, is 1,265,000,000 years. Potassium-argon dating has been used to measure the ages of a wide variety of objects up to 4,500,000,000 years old.

• The popular Carbon-14 dating is accurate to 50,000 years old.

• The accuracy of potassium-argon dating declines, however, for dates more recent than about a million years ago.

Graphic from FactMonster.comhttp://www.factmonster.com/dk/science/dinosaurs/dating-fossils.html

Calculate Half-lifeCalculate Half-life

• The half life of Iodine-131 is 8.1 days.

• How much of a 20g sample will be left after 32.4 days?

• Bonus:What does 131 refer to? Graphic from: Georgia College & State University

Professor: Dr J Metzker

• Using all your research, work with your group of fellow Paleontologists to create this part of your presentation that you submit for a shared grade. Consider using one slide per number to assure that you’ve addressed everything.

• The following information (and diagrams for each) must be included in your PowerPoint:

1. How the movement and separation of continents affected the organisms living on land in earth’s distant past.

2. How the evidence for plate tectonics contributes to the theory of evolution.

3. How fossils form and how they can be dated.4. Information on Paleontology and what Paleontologists do.5. Answer the fundamental question from the Paleontologist point of

view: “How does your research provide evidence that all living organisms have common ancestry but have changed across time?”

AssignmentAssignment