Academic journal article The American Biology Teacher

Exploring the Diversity of Life with the Phylogenetic Collection Lab

Academic journal article The American Biology Teacher

Exploring the Diversity of Life with the Phylogenetic Collection Lab

Article excerpt


An awareness of the extensive diversity of living organisms is an essential component of a complete biology education. It is important for students to explore the spectacular variety of living things as well as to understand the many solutions to the challenges of living on Earth that have evolved in different organisms. The National Science Education Standards (NRC, 1996) require that K-12 students understand that "the great diversity of organisms is the result of more than 3.5 billion years of evolution that has filled every available niche with life forms" and that "organisms are classified into a hierarchy of groups and subgroups based on similarities which reflect their evolutionary relationships" (p. 185). At the college level, Bio 2010 (NRC, 2003) states that biology undergraduates should understand that, "although fundamental molecular and cellular processes are conserved, biological systems and organisms are extraordinarily diverse" (p. 33). Most biology textbooks contain extensive descriptions of the diversity of living things; virtually all general biology courses, at the high school and introductory college level, spend a significant amount of time on this subject.

The data described in this article show that introductory-level biology students at the University of Massachusetts Boston have a very limited awareness of the diversity of living organisms. When most of these students are asked to name different animals and plants, their responses are almost exclusively members of two phyla: chordata and angiospermae. In order to meet the Standards described above, it is important that students realize that these two phyla represent only a tiny fraction of the diversity of life on Earth. This article describes a lab exercise, the Phylogenetic Collection Lab, designed to expand students' knowledge of diversity. In this lab, students collect samples of organisms from 12-16 different phyla that they have chosen from a list of 81 phyla, and discuss their similarities and differences. The data presented here show that this lab exercise significantly increases students' awareness of plant and animal diversity.

* Course Context

General Biology II (Bio 112) is the second-semester introductory course for biology majors. The course takes place over a 16-week semester; each week consists of three 50-minute lectures given by the author and one three-hour lab led by graduate teaching assistants (TAs). Typically, there are 150-200 students enrolled; most of these are biology majors, some are post-baccalaureate pre-medical students, and a few are majors in other departments. In the spring of 2007, when this study was conducted, there were 185 students enrolled in the course.

* The Phylogenetic Collection Lab

The Phylogenetic Collection Lab consists of two parts. The first part takes place over the several weeks before the Phylogenetic Collection Lab session meets; during this time the students collect their specimens. The purpose of this part is to provide a compelling illustration that there is far more to the diversity of life than chordata and angiospermae. The second part takes place in lab where the students present their collections and discuss what they have found. The purpose of this part is to experience the diversity of life: to compare and contrast the different solutions to challenges that all organisms face and to see the similarities and differences that are used to classify living things.

Specimen Collection

The first part takes five to 14 weeks, depending on the constraints of the semester's schedule. During this time, the students work in groups of one to three to collect specimens of organisms from a specified number of different phyla--in different semesters this has varied between 12 and 16. These specimens must be actual physical samples of the organisms themselves, not photographs, models, or drawings. Students can collect from any phyla of their choosing from a list of 81 phyla provided on the course Web site (http://intro. …

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