androdioecy animal colouration animal sexual behaviour anisogamy ant biological dispersal biology bird chromosomal crossover chromosome cloaca clownfish cone conjugation developmental biology digital object identifier eukaryote evolution external fertilization female fern field cricket fish flagellum flower gamete gender genetics gestation handicap principle haplodiploid sex-determination system heredity hermaphrodite honey bee hoverfly human human sexuality insect insemination internal fertilization intraspecific competition intromittent organ isogamy malaria male mammal mating mating in fungi mating system mating type meiosis mitosis mushroom organism ovary ovule penis pine plant sexuality pollen pollination polygyny protist reptile seed semen sex-determination system sex differences in humans sex ratio sexual conflict sexual dimorphism sexual dysfunction sexual intercourse sexual reproduction sexual selection sperm spore stamen temperature-dependent sex determination testicle turtle uterus vagina wrasse zw sex-determination system