Review Questions for Honors 301T

HOL Ch. 8: Leaving the Water

1. What are some major challenges faced by plants and animals in order to colonize land? Why is it plausible that the groups of organisms that were successful in colonizing land already had attributes that predisposed them for the transition to land? In other words, how could adaptations to life on land actually be beneficial and be selected for in organisms that were primarily aquatic?

2. Approximately characterize the important changes in land plant communities from the Silurian, Early, Middle, and Late Devonian, to Carboniferous (Mississippian + Pennsylvanian) Periods. What were the dominant plants? What major new innovations characterized these plants in each successive time interval? For help in this question, refer especially to Figures 8.2 to 8.7.

3. Compare plants and animals on land with respect to vulnerability to extinction by competition, climatic changes, and mass mortality events. Be able to defend your assertions.

4. Of all the groups of animals in marine habitats, which ones were successfuly in colonizing terrestrial (land) habitats?

5. Compare fins and extent of air breathing in coelacanths (see p. 92) and osteolepiforms (Osteolepimorpha or aquatic "rhipidistians").

6. Compare the problems of obtaining oxygen and getting rid of carbon dioxide for aquatic and land animals. Besides such gas exchange, what are some other possible reasons why it might be an advantage to spend at least part of the time out of water?

7. Compare and contrast a osteolepiform such as Osteolepis (see p. 103) to Ichthyostega. Using this link to Jenny Clack's website, also bring Acanthostega into this comparison. Given the evidence that Clack has emphasized, which of these differences were likely already present in aquatic ancestors?

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revised 8/25/07 - de