abdomen abdominal cavity animal anisogamy asexual reproduction australia bacteria bacterial conjugation bird bryophyte calorie cervix chemotaxis childbirth chorion clade cloaca dna dog ejaculation embryo embryogenesis equisetum eukaryote evolution of sexual reproduction extant fallopian tube fern fertility flowering plant fossil fruit gametophyte gestation period giraffe guppy hamster hermaphrodite hornwort immune system implantation infant isogamy karyogamy liatris liverwort lycopodium marsupial mating in fungi menstrual cycle mitosis monotreme morphogenesis moss new guinea nipple nutrient nutrition offspring oogenesis operational sex ratio organism ovary ovum parthenogenesis penis placenta plant plant sexuality poecilia pollen pollination pregnancy psilotum reproduction reptile resting spore rhizome self-pollination semen seta sex sex organ sexual dimorphism sexual intercourse sexual maturity spermatophore spermatozoon sporangium spore sporophyte stamen stenian testicle thallus thermoregulation umbilical cord uterus vagina vitamin zygote