Key terms
110 terms- Sexual reproduction§51.1
- Meiosis makes haploid gametes that fuse at fertilization into a diploid zygote
- Asexual reproduction§51.1
- Mitosis from one parent makes genetically identical offspring
- Fission§51.1
- A single-celled parent splits into two separate identical organisms
- Budding§51.1
- A piece of the parent separates and differentiates into a new individual
- Parthenogenesis§51.1
- Offspring develop from unfertilized eggs; all such parents are female
- Haploid-diploid system§51.1
- Bee and ant sex determination: haploid males, diploid females, no sex chromosomes
- Zygote§51.1
- The diploid fertilized egg — the first diploid stage of a new organism
- Hermaphroditism§51.1
- One individual carries both testes and ovaries
- Sequential hermaphroditism§51.1
- Changing sex over a lifetime rather than holding both at once
- Protogyny§51.1
- "First female" — female-to-male sex change (bluehead wrasse)
- Protandry§51.1
- "First male" — male-to-female sex change
- Temperature-dependent sex determination§51.1
- Environmental sex determination in many fish and reptiles
- Heterogametic sex§51.1
- The sex with two different sex chromosomes — male in mammals, female in birds
- SRY gene§51.1
- Sex-determining region of the Y; turns indifferent gonads into testes
- Indifferent gonads§51.1
- Undifferentiated embryonic gonads that can become testes or ovaries
- Primordial germ cells§51.1
- Cells that migrate from the yolk sac into the embryonic gonads
- Turner syndrome (XO)§51.1
- One X, no Y — develops female; evidence that Y presence drives maleness
- Klinefelter syndrome (XXY)§51.1
- Extra X but a Y present — develops male
- External fertilization§51.2
- Gametes unite outside the body, usually in water
- Internal fertilization§51.2
- Sperm are placed inside the female tract; required for live birth
- Spermatophore§51.2
- Gelatinous sperm packet deposited by male salamanders
- Intromittent organ§51.2
- Any structure used to transfer sperm into the female
- Hemipenes§51.2
- Paired copulatory organs of snakes and lizards
- Amplexus§51.2
- Mating clasp of frogs and toads during external fertilization
- Oviparity§51.2
- Internally fertilized eggs are laid and develop outside the mother
- Ovoviviparity§51.2
- Eggs retained inside the mother but nourished by yolk; born live
- Viviparity§51.2
- Young develop inside the mother, nourished by her blood via a placenta
- Amniotic egg§51.2
- Shelled egg with an amnion-enclosed fluid cavity; the key land adaptation
- Amnion§51.2
- Membrane enclosing the fluid-filled cavity around the embryo
- Chorion§51.2
- Extraembryonic membrane lining the shell; also forms the mammalian placenta and makes hCG
- Allantois§51.2
- Extraembryonic membrane of the amniotic egg
- Yolk sac§51.2
- The only extraembryonic membrane in fish and amphibian eggs
- Albumin§51.2
- Egg-white protein added around a bird egg in the oviduct
- Estrus§51.2
- Period of sexual receptivity around ovulation — "in heat"
- Estrous cycle§51.2
- Cycle of non-primate mammals; lining reabsorbed, no bleeding
- Menstruation§51.2
- Shedding of the uterine lining with bleeding; humans and apes only
- Induced ovulator§51.2
- Species that ovulates only after mating via reflex LH release (rabbits, cats)
- Monotreme§51.2
- Oviparous mammal — platypus and echidna; young lick milk from the skin
- Marsupial§51.2
- Viviparous mammal born very underdeveloped, finishing growth on a nipple in the pouch
- Placenta§51.2
- Chorion plus uterine lining; brings fetal and maternal vessels close for diffusion
- Seminiferous tubules§51.3
- Coiled tubules of the testis where sperm are produced
- Leydig cells§51.3
- Interstitial cells between tubules that secrete testosterone under LH
- Sertoli cells§51.3
- Nongerminal nurse cells stimulated by FSH; secrete inhibin and strip spermatid cytoplasm
- Testosterone§51.3
- Main androgen; builds male genitalia, secondary sex characteristics, and sperm
- Inhibin§51.3
- Peptide from Sertoli cells that suppresses FSH specifically
- GnRH§51.3
- Hypothalamic hormone that makes the anterior pituitary release FSH and LH
- Spermatogonium§51.3
- Diploid germ cell at the outer tubule wall; mitosis keeps the supply going
- Primary spermatocyte§51.3
- Diploid cell (46 duplicated chromosomes) that enters meiosis I
- Secondary spermatocyte§51.3
- Haploid product of meiosis I; chromosomes still have two chromatids
- Spermatid§51.3
- Haploid product of meiosis II — four per primary spermatocyte
- Spermatozoon§51.3
- Mature sperm: head with acrosome, midpiece with mitochondria, flagellar tail
- Germinal epithelium§51.3
- Tubule lining of spermatogonia, developing gametes, and Sertoli cells
- Acrosome§51.3
- Golgi-derived enzyme cap on the sperm head that penetrates the egg layers
- Epididymis§51.3
- Coiled tube where sperm sit at least 18 hours to become motile
- Vas deferens§51.3
- Tube carrying sperm from the epididymis toward the ejaculatory duct
- Seminal vesicles§51.3
- Paired glands adding fructose-rich fluid — about 60% of semen
- Prostate gland§51.3
- Adds milky alkaline fluid — about 30% of semen
- Bulbourethral (Cowper’s) glands§51.3
- Paired pea-sized glands adding ~10% lubricating fluid before intercourse
- Ejaculatory duct§51.3
- Continuation of the vas deferens that joins the urethra inside the prostate
- Semen§51.3
- Sperm (~1% of volume) plus seminal vesicle, prostate, and bulbourethral fluids
- Scrotum§51.3
- External sac holding the testes at ~34 °C, below the 37 °C core
- Inguinal canal§51.3
- Opening through which the testes descend into the scrotum before birth
- Corpora cavernosa§51.3
- Paired dorsal erectile columns of the penis (also in the clitoris)
- Corpus spongiosum§51.3
- Single ventral erectile column surrounding the urethra
- Baculum§51.3
- Penile bone present in most mammals but absent in humans
- Ovarian follicle§51.4
- Ovarian structure holding a primary oocyte plus granulosa cells
- Primary oocyte§51.4
- Diploid egg cell arrested in prophase of meiosis I since before birth
- Granulosa cells§51.4
- Cells surrounding the oocyte that secrete estradiol
- Estradiol§51.4
- Main female sex hormone; drives follicle growth signals, endometrial proliferation, secondary sex characteristics
- Progesterone§51.4
- Completes uterine preparation for implantation; dominant in the luteal phase
- Menarche§51.4
- Onset of menstrual cycling at puberty
- Follicular phase§51.4
- Ovarian cycle days 1–13; FSH matures the dominant follicle
- Graafian follicle§51.4
- Fully mature late tertiary follicle — a thin-walled blister on the ovary
- Secondary oocyte§51.4
- Large haploid cell from meiosis I, arrested at metaphase II and ovulated
- Polar body§51.4
- Tiny cytoplasm-poor byproduct of unequal oocyte division; up to three per oocyte
- LH surge§51.4
- Midcycle spike in LH, triggered by rising estradiol, that ruptures the follicle
- Corpus luteum§51.4
- The ruptured follicle converted by LH; secretes estradiol and progesterone
- Luteal phase§51.4
- Ovarian cycle days 15–28, dominated by the corpus luteum
- Luteal regression§51.4
- Degeneration of the corpus luteum late in an unfertilized cycle
- Endometrium§51.4
- Uterine lining of simple columnar epithelium that thickens and sheds each cycle
- Proliferative phase§51.4
- Uterine days 5–13; estradiol drives endometrial growth
- Secretory phase§51.4
- Uterine days 15–27; progesterone makes the lining vascular, glandular, glycogen-rich
- Menstrual phase§51.4
- Uterine days 0–5; the lining sheds with bleeding after hormones crash
- Fimbriae§51.4
- Feathery projections that sweep the ovulated oocyte into the Fallopian tube
- Fallopian tube§51.4
- Oviduct carrying the ovum to the uterus; site of fertilization in its upper third
- Cervix§51.4
- Narrow neck of the uterus opening into the vagina
- Blastocyst§51.4
- Hollow ball of cells that reaches the uterus and implants
- hCG§51.4
- Human chorionic gonadotropin — LH-like hormone from the embryonic chorion; maintains the corpus luteum and is what pregnancy tests detect
- Bartholin’s glands§51.4
- Paired glands near the vaginal opening secreting lubricating fluid
- Hymen§51.4
- Membrane partly covering the vaginal entrance until disrupted
- Uterine horns§51.4
- Paired uterine divisions in non-primate mammals, each leading to an oviduct
- Oxytocin§51.4
- Stimulates uterine contraction and the milk-ejection reflex
- Prolactin§51.4
- Stimulates milk production
- Birth control§51.5
- General term for pregnancy prevention
- Contraception§51.5
- Birth control acting before implantation
- Oral contraceptive§51.5
- Progesterone analogs (± estrogen) that suppress FSH/LH and block ovulation
- IUD§51.5
- Intrauterine device preventing implantation by irritation; ~1% failure
- Morning-after pill§51.5
- Emergency contraceptive with ~50× the estrogen of a regular pill
- Vasectomy§51.5
- Male sterilization — the vas deferens is cut and tied
- Tubal ligation§51.5
- Female sterilization — each Fallopian tube is cut and tied
- Infertility§51.5
- No conception after 12 months of unprotected intercourse
- Pelvic inflammatory disease (PID)§51.5
- Bacterial infection blocking the Fallopian tubes; leading global cause of infertility
- Endometriosis§51.5
- Endometrial tissue outside the uterus; scarring blocks egg transfer
- Premature ovarian failure (POF)§51.5
- Diminished egg supply in a woman under 40
- Hypogonadotropic hypogonadism§51.5
- Infertility from reduced GnRH; also caused by excessive exercise or anorexia
- Clomiphene (Clomid)§51.5
- Competitive estrogen-receptor inhibitor that blocks feedback so FSH and LH rise
- Artificial insemination§51.5
- Sperm introduced artificially into the female tract
- GIFT§51.5
- Gametic intrafallopian transfer — sperm and egg placed together in the tube
- IVF / embryo transfer§51.5
- Fertilization outside the body, then the embryo is transferred to the uterus
- ICSI§51.5
- Intracytoplasmic sperm injection — one sperm injected directly into the egg