For 2026: Please note that units are considered "under revision" until two weeks before the class date, and page content, web assignments, and exercises may change before that deadline.

Unit 13: Plant Classification

Preparation

• History Web Lecture: The web readings this time take us to a college student's discussion of the differences in the classification of plants by Theophrastus and Dioscorides, two Greek botanists. Theophrastus is a student of Aristotle's, and his interest in classifying plants is similar to that of a "pure" scientist. He uses an anatomical approach, identifying plant structures and their functions, and grouping plants by similarities in these areas. Dioscorides approach is very different: he is a doctor writing an herbal, a book about the medicinal qualities of the plants he collects, so he groups his plants by the types of disease that the plant can cure or alleviate.

  We have now spent three sessions on biological topics, all of them centered in the problems of classification. These problems are not restricted to biology but permeate all areas of knowledge. We need to classify information in order to "keep track" of it and find it again, but we also need to avoid the perils of judging something entirely by its assigned class. Classification systems can lead us to look at only certain characteristics, and miss others that may help us understand better the function of a given individual object in nature, or a person in society.

• Science Web Lecture: The weblecture provides some additional information for the different classes of plants.

• Homework: The mastery exercise questions require a fairly accurate reading of the article on Theophrastus and Dioscorides. Not a lot of interpretation and application is required in this particular assignment.

• Discussion:
  • How do our assumptions shape our classification systems?
  • What are the advantages and disadvantages of having more than one classification system for a given area of knowledge or type of thing?
  • What are the types of characteristics that we use to classify plants?
  • How do plants reproduce?

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