Stephen P. Broker
The teaching of evolution is certainly one of the most difficult aspects of any life science course. This subject requires of the student an appreciation of the concepts of time and of change not the time durations of our own experiences (hours, days, years), rather, periods of thousands and millions of years. Geological change presents enough problems in comprehension. Rapid cataclysmic change, such as the recent volcanic eruptions of Mount St. Helens in Washington, catches our attention, but the more gradual forces of nature action of the wind and waves, slow erosion, sedimentation, continental drift can be understood only with a deeper insight. To accept the notion of long term biological change is something which requires a fair amount of substantiation, particularly when religious views seem to be in conflict with scientific thought.
I believe that too frequently the student is not given sufficient opportunity to examine the evidence for organic evolution. It is difficult to appreciate such a fundamental theory of biological science when one doesn’t have ample time to learn about it. The Smithsonian Institution’s Museum of Natural History has recently opened an exhibit on evolution, which emphasizes the unifying aspects of the theory. In this exhibit, the effort has been made to illustrate population growth, competition, natural selection, adaptive radiation, mimicry, parallel and convergent evolution, by providing as many visual examples as space will allow. The overall effect is to understand the processes by being surrounded by the products of evolution.
This unit attempts to take a similar approach to the study of plant evolution. The topic is discussed primarily in terms of paleobotanical evidence, as well as through an examination of living plant species. The objectives of the unit are as follows:
1. to strengthen the student’s understanding of the basic principles of evolution, as applied to the plant kingdom, through readings, classroom activities, and laboratory activities.
2. to develop in the student a greater awareness of the concepts of time and ecological change.
3. to consider the several methods of fossilization of plant tissues; 4. to present a brief review of the diversity of plant life, discussing some of the differences among plant in the context of evolutionary developments;
5. to provide an overview of the evolution of plants, with particular emphasis on the evolution of land plants;
6. to discuss some of the most notable of fossil plant species;
7. to familiarize the student with herbaria and with the procedures for preparing herbarium specimens.
Laboratory and field activities focus on the diversity of plant life and on the examination of preserved plant remains.
Paleobotany is an area of science which can require a strong science background and very sophisticated thinking. It is not the intention of this unit to be so involved and complicated that the average student will be unable to deal with the material. The chances are small that any one of my students will become a paleobotanist, this year or in ten years’ time. In presenting this material in the classroom, then, the greater emphasis is put on developing a better understanding of the concepts of time, physical and biological change, and the diversity of life.
Those changes in plants regarded as most significant are the invasion of the land, the development of seed plants, and the appearance of the angiosperms (flowering plants). The major divisions of plants will be considered in relation to their ability to survive on land, exploit ecological niches on land, and reproduce efficiently.