1. Molecular sequence data are helpful, but these data should be considered carefully. Molecules change over time at different rates. Some are quite highly conserved. Certainly any tree based on a single character is incomplete, and it is better to include an array of characters. Molecular data from extinct forms are not available except in special instances of preservation.

2. What specific questions do you have about these topics? By yourself, or better yet, in a group, make a list of what you already know about this case in the “What Do I Know?” column. List questions you would like to learn more about in the “What Do I Need to Know?” column.

3. Put a check mark by 1–3 questions or issues from the “What Do I Need to Know?” list that you think are most important to explore.

4. What kinds of references or resources would help you answer or explore these questions? Identify two different resources and explain what information each resource is likely to give that will help you answer the question(s). Choose specific resources.

Memorandum

To: Miles Harrington, BioConsulting Associates

Re: Carboniferous Mural

Date: November 19, 2008

Enclosed are comments on the mural design for the new science building at Colter College. The stated goals of the mural project are to: (1) situate well in the local community, (2) relate to the donor’s connection to the coal industry, and (3) serve as a resource for teaching science.

The Carboniferous period is an appropriate choice for the mural, as there is a strong scientific connection to the region’s history of coal mining and the donor’s interests. However, your drawings of a swampy forest of the Carboniferous fall short. A similar conception of the Carboniferous is found in many museums, but it fails to emphasize several significant events of the period. Further, it gives the impression of a single climate—tropical—when in fact there were major glaciations with corresponding drops in sea level and increases in arid zones. Fossils of the period provide evidence of adaptive radiation of previously established terrestrial organisms such as seed plants, tetrapods, and insects.

The climatic changes in the Carboniferous were a significant factor in the evolution of plant communities, which changed in composition during wet and dry periods. During the periods of ice age, the vast swamps diminished as drier upland habitats became available. Instead of tree size lycophytes—a common feature of tropical swamps—conifers and seed ferns were dominant species forming the upland forest. Throughout the period, a wide variety of structural adaptations resulted in taller plants.

Although internal fertilization was well established previously, the first amniotes were tetrapods that produced shelled eggs during the Carboniferous. This enabled reproduction as well as embryonic development away from water for both synapsids (reptilelike ancestors to modern mammals) and reptiles. Another major development during the early Carboniferous was flight in insects. A tremendous radiation of flying insects is seen in the fossil record by the end of the Carboniferous.

While the Carboniferous was a time during which terrestrial habitats were well exploited by an increasing variety of life forms, keep in mind that many of the early adaptations for living on land, such as the insect exoskeleton, tetrapod body shape, and plant vascular tissue, arose during earlier geologic periods. We think that Wall Works, Inc., has a real opportunity to create a mural that richly illuminates the Carboniferous in a way that can serve the regional and educational communities. Let us know if we can be of further assistance.