Abstract:

Zoology is an integral subject of the four-year Biology Degree in Spanish Universities that is usually taken during the first or second academic year. Given the key role of zoology as a descriptive foundation for other disciplines, and the tight schedules to develop contents, emphasis is given to a functional and evolutionary account of adult body plans and diversity patterns. This sensible approach, however, hampers an in-deep treatment of the extraordinary diversity of animals' life cycles, which requires a great deal of integration to foster significant learning in students; otherwise, students could end up just memorizing a number of life cycles and names of larvae. In this presentation, we propose a single-session activity (2 h) devoted to understand major ecological and evolutionary principles behind animals' life cycles, with a special focus on the differences between direct and indirect (i.e., with larvae) cycles. The activity is devised for small-groups (up to 16 students) and is scheduled after lectures dealing with at least several invertebrate phyla (e.g., Porifera, Cnidaria, Platyhelminthes, Annelida and Mollusca).

The structure of the activity is as follows:
(1) Before the face-to-face session, the students are requested to condense basic data on the life cycles and names of larvae (if any) of the phyla dealt with in lectures;
(2) in the face-to-face session, students, working in groups, are asked to find patterns in the occurrence of larvae (e.g., when adults are sessile);
(3) a discussion follows, in which students agree about the regularities they have found;
(4) students are then asked to create a conceptual map that explains the adaptive advantages of having / lacking larval stages;
(5) students share their conceptual maps and, after a discussion, a merged map is agreed upon.

The activity is evaluated through:
(1) quality of the individual report on larval types;
(2) active participation during the discussion, and
(3) a problem in the theory exam. In the latter, students are asked to predict whether, and why, the life cycle of an animal from a phylum they have not dealt with in theory lectures should contain larval stages.

In our experience, the activity has clear pedagogic virtues. First, students must review their factual acknowledge about life cycles and larval types. Second, students must search functional principles to integrate information, and this strongly facilitates meaningful learning. In fact, students could readily apply these principles to new contexts (e.g., to understand the life cycles of plants). Third, students work on concepts that will serve as a basis for upper-level subjects (e.g., ecology). Finally, the activity is cost-effective because it is little time-consuming.

Keywords:

Zoology, life cycle, significant learning, larvae.