IB Biology D 3.1: Human and Animal Reproduction

Comprehensive vocabulary flashcards covering human and animal reproduction topics, including asexual versus sexual reproduction, reproductive anatomy, gamete morphology, the menstrual cycle, fertilization, IVF, and sources of meiotic variation.

Asexual Reproduction

A reproductive process by which a single parent passes on genetic information to produce genetically identical offspring without the use of gametes or fertilization.

Sexual Reproduction

A reproductive process involving two parents where specialized haploid sex cells fuse during fertilization to form a genetically unique diploid offspring.

Mitosis

A form of asexual division in eukaryotic cells that produces two genetically identical daughter cells with $46$ chromosomes, utilized for tissue growth and bodily repair.

Binary Fission

A form of asexual reproduction occurring in prokaryotic organisms, such as bacteria, where the genetic material duplicates and the single cell splits into two identical cells.

Budding

A form of asexual reproduction found in fungi (such as yeast) and organisms like Hydra, where duplicated DNA moves into a small outpouching of the plasma membrane that separates from the parent cell.

Fragmentation

An asexual reproductive mechanism in organisms such as sea stars and certain worms where a detached body segment develops into a complete, functioning organism.

Parthenogenesis

The growth and development of an unfertilized egg cell into a complete organism without the involvement of a male gamete, observed in bees, ants, wasps, and certain reptiles.

Vegetative Propagation

A method of asexual reproduction in plants, such as strawberries using horizontal underground stems called runners, to grow new genetically identical plants.

Gametes

Specialized reproductive sex cells (sperm and egg) produced via meiosis that contain a haploid number ($23$) of chromosomes.

Zygote

The first diploid cell containing $46$ chromosomes formed by the fusion of a sperm cell and an egg cell during fertilization.

Diploid

A cell that possesses two complete sets of chromosomes ($46$ chromosomes in humans), with one maternal copy and one paternal copy for each chromosome pair.

Haploid

A cell that possesses a single set of unpaired chromosomes ($23$ chromosomes in humans), typical of mature sperm and egg cells.

Testes

The male reproductive organs located outside the abdominal cavity that are the site of meiosis (spermatogenesis) and testosterone production.

Seminiferous Tubules

Tightly coiled microscopic tubes within the testes where sperm cells are specifically generated through spermatogenesis.

Epididymis

A coiled crescent-shaped structure resting atop the testes where immature sperm are stored and undergo maturation to become motile.

Vas Deferens

The long muscular tube (also termed the sperm duct) that propels mature sperm from the epididymis toward the urethra during ejaculation.

Seminal Vesicle

A male accessory gland that secretes a nutrient-rich fluid containing fructose into the vas deferens to provide energy for sperm motility.

Prostate Gland

A gland surrounding the vas deferens and urethra that secretes an alkaline fluid to neutralize vaginal acidity and protect sperm viability.

Semen

The fluid ejaculated by the male, composed of approximately $3\%$ sperm cells combined with fructose secretions from the seminal vesicles and alkaline fluids from the prostate.

Scrotum

The external sac of skin holding the testes outside the body to keep them at a cooler temperature than internal body heat ($37^\circ\text{C}$) for proper sperm development.

Urethra

The duct passing through the penis that serves as a shared exit passage for both urine from the bladder and semen during ejaculation.

Ovary

The female reproductive organ responsible for producing egg cells via oogenesis, releasing mature eggs during ovulation, and secreting estrogen and progesterone.

Fallopian Tube (Oviduct)

The tube with finger-like projections that captures an ovulated egg from the ovary and provides the typical site where fertilization takes place.

Uterus

The hollow, thick-walled muscular organ in the female pelvis where a fertilized zygote implants and develops into a fetus.

Endometrium

The highly vascular inner mucosal lining of the uterus that thickens to support embryo implantation and sheds during menstruation if no pregnancy occurs.

Cervix

The narrow muscular neck located at the lower opening of the uterus connecting directly to the upper vagina.

Acrosome

A specialized organelle located at the tip of the sperm head containing digestive enzymes required to penetrate the protective outer coats of the egg.

Zona Pellucida

A tough glycoprotein envelope surrounding the mammalian egg cell that must be enzymatically broken down by sperm acrosome enzymes during fertilization.

Corona Radiata

An outer protective mantle of follicular cells surrounding the unfertilized egg that provides physical protection and nutritional support.

Cortical Vesicles

Membrane-bound vesicles within the egg cytoplasm that release their enzymatic contents upon sperm penetration to harden the zona pellucida and permanently block polyspermy.

Menstrual Cycle

A recurring hormone-regulated cycle lasting roughly $28\text{ days}$ in human females that coordinates egg development in the ovaries and prepares the uterine endometrium for pregnancy.

GnRH (Gonadotropin-Releasing Hormone)

A peptide hormone produced by the hypothalamus that travels to the anterior pituitary gland to stimulate the secretion of FSH and LH.

FSH (Follicle-Stimulating Hormone)

An anterior pituitary hormone that stimulates the growth of an immature oocyte into a mature Graafian follicle and prompts follicular cells to secrete estrogen.

LH (Luteinizing Hormone)

An anterior pituitary hormone whose dramatic surge around day $14$ triggers ovulation and converts the remaining follicular cells into the corpus luteum.

Graafian Follicle

The mature, fluid-filled ovarian follicle containing a mature egg surrounded by specialized estrogen-secreting follicular cells prior to ovulation.

Estradiol (Estrogen)

A steroid hormone secreted by ovarian follicular cells that initiates endometrial vascularization and thickening, switching to positive feedback at high concentrations to trigger the LH surge.

Ovulation

The release of a mature egg from the Graafian follicle in the ovary into the fallopian tube, stimulated by the surge in luteinizing hormone at approximately day $14$.

Corpus Luteum

A temporary endocrine structure ('yellow body') formed from remaining follicular cells after ovulation that secretes progesterone for approximately $10$ to $12\text{ days}$.

Progesterone

A hormone produced by the corpus luteum that maintains the thickened vascular endometrium and suppresses FSH and LH via negative feedback to prevent new follicles from developing.

Menstruation

The shedding of the vascular endometrial lining and associated blood through the vagina, marking day $1$ of the menstrual cycle following a drop in progesterone levels.

In Vitro Fertilization (IVF)

An assisted reproductive procedure in which eggs are hormonally stimulated and retrieved, fertilized by sperm in a laboratory, and the resulting embryo is transferred into the uterus.

Superovulation

The clinical stimulation of an ovary using artificial gonadotropin hormone therapy to produce and mature multiple eggs simultaneously during an IVF cycle.

Crossing Over

The reciprocal exchange of genetic segments between non-sister chromatids of homologous chromosomes during prophase I of meiosis, creating novel combinations of maternal and paternal alleles.

Independent Assortment

The random orientation and segregation of maternal and paternal homologous chromosome pairs along the metaphase plate during meiosis, generating unique combinations across gametes.

Random Fertilization

The chance union between any single genetically unique sperm cell and any single genetically unique egg cell, multiplying genetic variation among offspring.