Asexual Reproduction: reproduction without the union of “germ cells,” and consequently without their production. (Richards, 393) Reproductive strategy that occurs when offspring are produced from a single parent. The offspring are therefore clones of the parent. (Brooker, 1087) Reproduction without fusion of two types of cells, mostly found in “algae,”  “fungi,” and plants. Asexual reproduction occurs in several ways, such as ‘budding,’ and splitting from parent cells. Only a few groups of animals reproduce asexually. (MeSH)

Parthenogenesis: reproduction from a female gamete without without fertilization by a male gamete. (Lawrence) A unisexual reproduction without the fusion of a male and a female gamete (fertilization). In parthenogenesis, an individual is formed from an unfertilized “ovum” that did not complete “meiosis.” Occurs in nature and can be artificially induced. (MeSH)

Fertilization: broadly considered, the union of the “gametes” of two sexes. Strictly speaking it has two phases, initiation of development and the union of the egg and sperm. (Richards, 396) The process which involves the fusion of male and female gametes to produce a “zygote.” (Indge, 108) The fusion of the sperm and oocyte in the “fallopian tube.” (Patestas, 10) A sperm cell can survive in the woman's body for up to 3 days, but the oocyte can only be fertilized in the 12 to 24 hours after "ovulation." (Lewis, 53)

Cross Fertilization: fertilization where male and female gametes come from different organisms (i.e. not self-fertilized). (Indge, 72) The fusion of male and female gametes from different individuals, especially of different “genotypes.” (Lawrence)

Self-Fertilization: the fusion of male and female gametes from the same individual. (Lawrence) Fertilization where male and female gametes come from the same organism. (Indge, 72)

Gametogenesis: gamete formation. (Lawrence) The process of development of the mature gamete from a 'primordial' germ cell. (Richards, 396)

Germinal Period: (weeks 1-2 of "pregnancy" when) the zygote undergoes rapid cell division before becoming implanted on the wall of the mother’s "uterus." By the end of the germinal period, the single-celled zygote has developed into a cluster of cells called the embryo. (Hockenbury, 355)

Incubation: the process of development of an egg or a culture of “bacteria.” (OxfordMed) The growth of a culture of microorganisms by keeping it for some time at an optimum temperature. The hatching of eggs by means of heat, natural or artificial. (Lawrence)

Implantation: the process by which the mammalian “blastocyst” becomes attached to the “uterine” wall. (Richards, 398) A week after conception, the blastocyst nestles onto the uterine lining. This event, called implantation, takes about a week. As it starts, the outermost cells of the blastocyst secrete the 'pregnancy hormone' (human chorionic gonadotropin - hCG) which prevents menstruation. hCG detected in a woman's urine or blood is one sign of pregnancy. (Lewis, 54)

Chorion: the outermost layer of the membranous sac enclosing the embryo in higher vertebrates. (NCIt) The blood vessels are concentrated in the region of the chorion that is attached to the wall of the uterus and forms the "placenta." (OxfordMed) Embryonic membrane external to and enclosing the "amnion" and "yolk sac." (Lawrence)

Menstruation: discharge of unfertilized ovum plus layer of uterine wall that occurs periodically in humans and some other higher mammals. (Lawrence) Periodic discharge of blood and tissue from the uterus. From puberty until menopause, menstruation occurs about every 28 days when a woman is not pregnant. (NCIt) Formerly referred to as ‘menses.’

Menarche: onset of menstruation. (NCIt) A (human) female’s first menstrual period, which occurs during puberty. (Hockenbury, 375) First menstruation or age at first menstruation. (Lawrence)

Natal: of or pertaining to one’s birth. (Oxford)

Oogenesis: the development of ovum, which are the female germ cells. Oogenesis occurs by meiosis and is essential for the production of mature eggs. (NCIt) Meiosis in the female. Begins with a "diploid cell" called an 'oogonium.' (Lewis, 51)

Prenatal: before birth. (Oxford) The time period after impregnation and before birth. (NCIt) (Also description of) tests for genetic defects performed on a fetus in the womb. (Lawrence)

Reproductive Structures: includes "gonads" where the sperm and oocytes are manufactured, tubular structures that transport these cells, and hormones and secretions that control reproduction. Organized similarly in the male and female. (Lewis, 45)

Epididymis: tightly coiled tube in which sperm cells mature and are stored. (Lewis, 45) Mass at back of testicle composed mainly of (ducts) leading from "testes" to the 'vas deferens.' (Lawrence)

Fallopian Tube(s): tube that carries the oocyte into the uterus. (Lewis, 45) Either of a pair of tubes that conduct egg cells from the ovary to the uterus. (OxfordMed) One of a pair of narrow ducts in mammals each leading from an ovary to the uterus, into which ova are released on ovulation, and in which fertilization normally takes place. (Lawrence) Also referred to as ‘oviduct,’ and 'uterine tube.'

Gamete(s): sperm and egg cells and their "precursors." Germ cells are "haploid" and have only one set of chromosomes (23 in all). (HGPIA) A cell that is involved with sexual reproduction, such as a sperm cell or egg cell. (Brooker G-15) Provides a way to mix genetic material from past generations. (Lewis, 45) A male begins manufacturing sperm at puberty and continues throughout life, whereas a female begins meiosis when she is a fetus. (Lewis, 49) Also referred to as 'germ cells' and ‘sex cells.’

Oocyte: female germ cells derived from 'oogonia' and termed oocytes when they enter meiosis. (MeSH) A cell in the ovary that undergoes meiosis to form an ovum. (OxfordMed) Oocytes develop within the ovary. An ovary contains many oocytes in various stages of maturation. After puberty, the most mature oocyte in one ovary bursts out each month, in an event called ovulation. (Lewis, 52) Also referred to as 'ova,'  'egg,' and 'egg cells.’

Ovum: the female gamete ready for fertilization. (Richards, 400) A mature haploid female germ cell extruded from the ovary at ovulation. (MeSH) Plural - ‘ova.’

Sperm: a mature male sex cell. The tail of a sperm enables it to swim, which is important as a means for reaching and fertilizing the ovum. (OxfordMed) Each sperm cell consists of a tail, body, and a head region. A membrane-covered area on the front end, the 'acrosome,' contains "enzymes" that help the sperm cell penetrate the protective layers around the oocyte. Within the sperm head, "DNA" is wrapped around proteins. (Lewis, 50) Also referred to as ‘spermatozoa.’

Gonads: reproductive system organs that produce and release either “sperm” or “eggs.” (NCIt) The endocrine glands that secrete hormones that regulate sexual characteristics and reproductive processes. (Includes) “ovaries” in females and “testes” in males. (Hockenbury, 56)

Ovaries: the main female reproductive organs, which produce ova and “hormones” in a regular cycle. (OxfordMed) The reproductive organ in which female gametes (or egg cells), are produced. (Lawrence) Paired organs in the abdomen where the female sex cells develop. Within each ovary of a newborn girl are about a million immature oocytes. (Lewis, 450) Singular - ‘ovary.’

Prostate Gland: a muscular and glandular organ around the beginning of the 'urethra' in the pelvic "cavity." (Lawrence) Produces a fluid that activates the sperm to swim. (Lewis, 45)

Seminal Vesicles: glands of male mammals, which "secrete" the "alkaline" fluid component of semen. (Lawrence) Secrete "fructose" and "prostaglandins," which may stimulate contractions in the female that help sperm and oocyte meet. (Lewis, 45)

Testes: male reproductive glands producing spermatozoa. (Lawrence) Paired oval organs in the male where sperm is manufactured. They lie outside the abdomen within a sac. This location keeps them cooler than the rest of the body, which is necessary for sperm to develop. (Lewis, 45)

Sexual Reproduction: reproduction involving the union of gametes of two individuals, and thus implying the steps necessary for gametogenesis. (Richards, 403) The production of a new individual by the joining of sperm from the male, and eggs from the female. The major difference between sexual reproduction and  asexual reproduction is that sexual reproduction allows for greater “genetic variation.” (Brooker, 1088)

Spermatogenesis: giving rise to sperm. (Lawrence) The formation of sperm cells. Begins in a diploid "stem cell" called a 'spermatogonium.' (Lewis, 50) The process of germ cell development in the male from the 'primordial' germ cells, through spermatogonia to the mature haploid spermatozoa. (MeSH)