The phenomenon known as "essentialism"--the belief that all species have an essential form with variation being a form of accident of aberration from the essence of the species--is widespread and important because it is at odds with biological reality. The prospect of teaching children about inheritance and evolution would be undermined if they assume that each individual within a species, and its offspring, is exactly the same. This report continues previous reports of Terry Russell and Linda McGuigan's Nuffield-funded project to explore the teaching and learning of evolution and inheritance. The authors describe how teachers used "The Tiny Seed," by Eric Carle, as the starting point to teach children to observe and measure variability in a number of contexts so as to appreciate the recurring "hill-shaped" pattern of given features within a population. Because evolution operates through populations rather than through individuals, opportunities for systematic measurement, interpreting patterns, and appreciating in some manner the nature of distributions are all important for later learning. Work of this kind provides a foundation for children's later consideration of changes in population distributions and an understanding of evolution by natural selection. [For the authors' previous reports, see "How Long Is a Piece of String? 4.5 Billion Years Perhaps!" (EJ1046916) and "Research into Inheritance and Evolution (with Dr Who's Help!)" (EJ1044249).]