have one. This system is found in several species of moths. Environmental For many species, sex is not determined by inherited traits, but instead by environmental factors such as temperature experienced during development or later in life. In the fern Ceratopteris and other homosporous fern species, the default sex is hermaphrodite, but individuals which grow in soil that has previously supported hermaphrodites are influenced by the pheromone antheridiogen to develop as male. The bonelliidae larvae can only develop as males when they encounter a female. Sequential hermaphroditism Some species can change sex over the course of their lifespan, a phenomenon called sequential hermaphroditism. Teleost fishes are the only vertebrate lineage where sequential hermaphroditism occurs. In clownfish, smaller fish are male, and the dominant and largest fish in a group becomes female; when a dominant female is absent, then her partner changes sex. In many wrasses the opposite is true—the fish are initially female and become male when they reach a certain size. Sequential hermaphroditism also occurs in plants such as Arisaema triphyllum. Temperature-dependent sex determination Many reptiles, including all crocodiles and most turtles, have temperature-dependent sex determination. In these species, the temperature experienced by the embryos during their development determines their sex. In some turtles, for example, males are produced at lower temperatures than females; but Macroclemys females are produced at temperatures lower than 22 °C or above 28 °C, while males are produced in between those temperatures. Haplodiploidy Other insects, including honey bees and ants, use a haplodiploid sex-determination system. Diploid bees and ants are generally female, and haploid individuals (which develop from unfertilized eggs) are male. This sex-determination system results in highly biased sex ratios, as the sex of offspring is determined by fertilization (arrhenotoky or pseudo-arrhenotoky resulting in males) rather than the assortment of chromosomes during meiosis. Sex ratio Sex differences Anisogamy is the fundamental difference between male and female. Richard Dawkins has stated that it is possible to interpret all the differences between the sexes as stemming from this. Sex differences in humans include a generally larger size and more body hair in men, while women have larger breasts, wider hips, and a higher body fat percentage. In other species, there may be differences in coloration or other features, and may be so pronounced that the different sexes may be mistaken for two entirely different taxa. Sexual dimorphism In many animals and some plants, individuals of