A causal explanation in biology focuses on the mechanism by which a biological process is brought about, whereas a teleological explanation considers the end result, in the context of the survival of the organism, as a reason for certain biological processes or structures. There is a tendency among students to offer a teleological explanation instead of a causal explanation when they are required to describe how a particular biological phenomenon is brought about. They have difficulty distinguishing between the end result, generally biological adaptation and survival, and the cause that leads to the end. In this paper, examples of causality and teleology are discussed, with reference to: photosynthesis, transpiration and transport of water up the plant via pull of transpiration; the human circulatory and respiratory systems, particularly exercise physiology. This paper also aims to suggest ways in which students can be taught to differentiate between causal and teleological explanations, for example, through the specific ways in which questions can be phrased, and by explicitly teaching students to identify the cause and significance of biological events. This will reduce misconceptions that students have about certain biological processes in organisms. (Contains 1 figure.)