 When considering that species without sex chromosomes possess all of the genes necessary to develop the phenotype of both sexes, it becomes apparent that the process of sex determination and sexual differentiation represents a form of phenotypic plasticity.Using the leopard gecko ("E. macularius") as the animal model system, Dr. Crews determined how the experience of temperature during a narrowly defined period of embryogenesis affects the total phenotype of the adult organism, accounting for much of the variation observed among individuals in morphology, growth, endocrinology, neural activity, and neuroanatomy.Some sociosexual behaviors and brain measures are affected directly by incubation temperature, whereas both incubation temperature as well as gonadal sex influences others.