Examining the Fossil Record

1. Examining the Fossil Record

4. Lab Investigation: Fictional genus Crustaceous

5. Objectives:* Analyze characteristics of fossils* Compare placement of fossils and determine relative ages* Develop a model evolutionary tree based on the morphology and age of fossils

6. Fossils are traces of organisms that lived in the past. • When fossils are found, they are analyzed to determine the age of the fossil. • The absolute age of the fossil can be determined though radiometric dating and determining the layer of rock in which the fossil was found. Older layers are found deeper within the earth than newer layers.

7. The age and morphologies (appearances) of fossils can be used to place fossils in sequences that often show patterns of changes that have occurred over time. • This relationship can be depicted in an evolutionary tree, also known as a phylogenetic tree.

8. There are two major hypotheses on how evolution takes place: gradualism and punctuated equilibrium.

9. Gradualism suggest that organisms evolve through a process of slow and constant change. • Example: an organism that shows a fossil record of gradually increased size in small steps, or an organism that shows a gradual loss of a structure.

10. Punctuated equilibrium suggests that species evolve very rapidly and then stay the same for a large period of time. This rapid change is attributed to a mutation in a few essential genes.

12. Procedure: 1a) Obtain lab instructions 1b) The CHART you are drawing requires a poster 2. Use a ruler to draw the lines on your chart.

14. Procedure: 3. Obtain a fossils sheet. 4. Cut each fossil, but leave the age of the fossil.

15. 5. Begin arranging the fossils by age on your chart. 6. Lower means “older” fossils, and “upper” means most recent fossil.

16. Not all fossils are represented, illustrating the incompleteness of any fossil record.

18. 8. If you have several fossils from the same period, place them by age order.

19. 9. While keeping the fossils in the proper age order, arrange them by morphology (appearance):

20. 10. Once all the fossils have been placed correctly according to time and morphology, glue the fossils in place.

21. 11. You need to graph your poster’s chart results!

23. Poster and Graph Results should match!

24. The number 0 on the Change in Morphology shows the appearance of the original (oldest) fossil. Each tick mark to either side denotes one fossil to the next-youngest fossil according to your poster results.

27. Get a 2nd sheet of fossils to create a drawing of an evolutionary tree on your graph paper. 25 20 15 10 5 0 5 10 15 20 25

28. Example of Phylogenetic Tree

29. Grading: Your 11 answers are worth 20 points each! Your graph is worth 100 points Your poster is worth 75 points

30. Analysis 1. Give a brief description of the evolutionary changes that occurred in Crustaceous. Refer back to the morphology of Crustaceous and use the terms used to describe the various body parts of the organism that have evolved. 2. During which period did the fossils start to differentiate into two branches? 3. How long did it take to differentiate into two branches? 4. In what period does the common ancestor of the Crustaceous species of the Montanian period appear? Conclusions: • No examples of Crustaceous survive today. Determine when the genus became extinct. Support your answer. • What did scientists use to determine the absolute age of the fossils found? Explain the process. • Did the set of fossils show gradualism or punctuated equilibrium? Explain. • Using Crustaceous, sketch an example of an evolutionary tree that shows punctuated equilibrium. • What is a fossil? • What do scientists do to categorize fossils? • Why is the fossil record evidence for evolution?