Activity: biodiversity patterns of speciation and extinction

Hint: the background information that will help you complete this activity is found in the videos and article.

This activity involves constructing a geologic timeline to show the relative lengths of the different time intervals, as well as major events that occurred during them, including mass extinctions.

Background: Have you ever wondered just how long ago a billion years is? In this activity, you will make and then travel along a scale model of Earth’s geologic history. Scientists have divided the geologic history of this planet into different time intervals. From largest to smallest, the intervals are eons, eras, periods, epochs, and ages. Eons are made up of eras, eras are made up of periods, and so on. During these intervals, there were great changes in Earth’s biodiversity, as documented by the fossil record.

During the Earth’s long history, five major mass extinctions significantly changed life on Earth. 

For more information on each eon, era, period, epoch, and age, explore the Smithsonian’s Story of a Changing Earth.  http://paleobiology.si.edu/geotime/main/

Materials:

·      a ruler, yard or meter stick, or tape measure

·      masking tape or chalk

·      14 index cards or pieces of paper

Procedure:

a)    Pick a suitable location to make your timeline. Find an area that has a long stretch of flat, uninterrupted pavement, grass, or dirt about 425 feet long (130 meters) or at least an area where you can curve around. This 425-foot stretch represents the entire 4.6 billion year history of Earth, from the planet’s formation to the present day. If you can’t find such a long space, you can divide all of the measurements below by 10, but the timeline won’t be as impressive, and the start of it will be hard to measure.

b)   Mark your starting point (modern day) with tape or chalk. Measure the distance from the starting point to the first time listed, which is 200,000 years ago. Mark that point with tape or chalk, and make a note about what the important event was. Continue in a straight line like this for each of the other 12 times listed in the chart. Note that the distances listed are all from the starting point. So you will have your starting point, and then a mark that is 0.221 inches (0.005 meters = 5.0 mm) from the starting point for 2,000 years ago; another mark in a straight line from the starting point and the 2,000-year mark at 2.212 inches (0.056 meters) from the starting point to represent 2 million years ago; the next mark in the same straight line at 5.530 inches (0.140 meters) from the starting point to represent 5 million years ago; and so on. Because the first few marks are such small distances, feel free to round them to just one decimal place (e.g., 0.2 inches = one-fifth of an inch)

​After creating your timeline, answer the following questions:

a)    What surprised you the most about this timeline?

b)   How do the distances on the timeline differ among the five major mass extinction events?

c)    Pick a point in time in the history of Earth at least one million years ago.  If you could go back in time and live the rest of your life in that time, what would you observe?  Consider how the world would look and what plants and animals might dominate the scenery. Would you expect to see a lot of species evolve or go extinct in the 80 or so years you might live?

d)   Consider the types of changes that occur over an interval of millions of years.  How different do you imagine the life and geology on Earth will look one to two million years from now?  What will the Earth be like 50 million years in the future?