Life Spirals: A Critique of Life Cycle Diagrams

Life cycle diagrams are ubiquitous in a variety of scientific materials, ranging from introductory biology textbooks to professional publications. These diagrams typically depict stages of a particular organism’s life connected by arrows, such as, for a frog: egg(s) → embryo → tadpole → tadpole with two legs → tadpole with four legs → young frog → adult frog → egg(s). In this paper, we present a critique of this sort of life cycle diagram, drawing on both metaphysics and epistemology of science. We suggest that these diagrams do not accurately represent an organism’s life stages, its reproduction, or species persistence. These misrepresentations have implications for scientific reasoning, explanatory efficacy, and pedagogical efficacy. To address the shortcomings of these diagrams, we propose a new kind of diagram which we call the life spiral diagram. The life spiral diagram more accurately reflects an organism’s life stages, its reproduction, and species persistence. Thus, the life spiral diagram better aids scientific reasoning, explanations of life processes, and learning.