Mechanisms of Change and the Fossil Record

Assignment Overview

Mass extinctions are periods in Earth's history when abnormally large numbers of species die out simultaneously or within a limited time frame. The Cretaceous-Tertiary (or K-T) extinction event is probably the most well-known to many people because it wiped out the dinosaurs, but many other mass extinction events have occurred throughout the history of the Earth. Some of these mass extinction events are even more devastating than K-T. The most severe occurred at the end of the Permian period when approximately 96% of all species disappeared. Many smaller scale mass extinctions of plants and animals have occurred as recorded in the fossil records. Discover more about Earth's major extinction events below in the following case assignment.

Case Assignment

STOP! Before you proceed, make sure that you have read the Home page for this module and followed the links provided there. This assignment requires information from those resources.

Case Part I: Geologic History of Earth

The first part of this assignment requires that you consider the history of extinction on our planet as explained in the links you viewed on the Home page. From the Museum of Paleontology tutorial on the Home page, answer the following questions. Use full sentences in paragraph form:

When you clicked on the "bookmarks," which events were listed and in what order (there were six)?

In the Geologic Time Scale section, images of which organisms are included in the Archaean time period?

Which three periods of time are described as "Eras"? List the representative organisms included in the photos that appear when you click on each Era.

From the Sam Noble Museum Mass Extinctions

How many major mass extinction periods are listed here? Follow the links from that page to learn more about each period. What caused each, and which major groups of species disappeared from each period?

Choose two of the recent extinctions listed on this link and explain how they occurred.

Case Part II: Global Climate Change

Scientists have concerns that human activities are changing our environment at rapid rates that could result in a sixth mass extinction. Let's examine the evidence:

Review this tutorial on the carbon cycle and greenhouse gases.

What were listed as human activities related to greenhouse gas production? What does this do to the rate at which carbon is returned to the atmosphere?

Opponents of the theory of global climate change propose that extinctions are a normal part of our planet's history and that the temperature of the planet has also historically fluctuated. Use the following Greenhouse Gas simulation. Begin by clicking on the "Simulation Controls" in the upper left-hand corner. Set the greenhouse gas level to the highest, check the boxes "view labels" and "view a possible consequence." Use the arrow in the lower right-hand corner to watch the interactive graph, then select "run" on the simulation control window.

When you click on the "Graph" menu, what is the relationship between percent (%) of greenhouse gases and temperature? What is the relationship between temperature and ice? Which mass extinction from the Natural History Museum website in Part I does this remind you of?

What role does human activity play in the current global warming trend?

Part III: Drawing Conclusions

Now provide a Conclusion paragraph that explains what conclusions you can make for yourself based on the evidence provided and what you now know about the geologic time scale of the history of the Earth. What questions are still left unanswered for you?

Assignment Expectations

Organize this assignment using Part I, Part II, and Part III, with a brief description as subtitles. Answer each question under the subtitle using complete sentences that relate back to the question. For example, Question 1 should be organized this way:

Part I: Geologic History of Earth

For example, when describing items you found in the tutorial, phrase your answers in complete sentences: "Using the Museum of Paleontology website, I found <> listed when I clicked on the bookmarks in the tutorial."

Be sure to include a references section at the end of your assignment in APA format that lists the websites used above and any additional resources you used to research your answers.