IB Biology Topic D3.1: Reproduction Key Definitions

The acrosome reaction is the first step in fertilization. It allows a sperm to penetrate the egg's protective glycoprotein layer, called the zona pellucida, to reach the plasma membrane of the egg.

Asexual reproduction is a process where a single parent produces offspring without the involvement of gametes (sperm and egg).

The cortical reaction is a process initiated during fertilization that prevents polyspermy, the fusion of multiple sperm with one egg.

Stimulates the growth of ovarian follicles and oestradiol production.

Also known as fertilization, combines two haploid gametes (sperm and egg) to form a diploid zygote. This process not only restores the chromosome number but also introduces additional genetic diversity.

The process by which cells undergo meiosis to form gametes.

Germination is the process by which a seed transitions from dormancy to active growth, developing into a seedling.

GnRH is a peptide hormone secreted by the hypothalamus in the brain. It regulates the reproductive system by stimulating the anterior pituitary gland to release two key hormones: luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

Any organism that can produce both male and female reproductive organs

HRT is a treatment that supplements the hormones oestrogen and progesterone, which naturally decline during menopause.

Hormones are chemical messengers that travel through the bloodstream to regulate various physiological processes.

Human chorionic gonadotropin (hCG) is a hormone essential for sustaining early pregnancy. It ensures that the uterine environment remains suitable for the developing embryo by maintaining the production of progesterone.

A region of the brain responsible for regulating many physiological processes, including the endocrine system. It sends signals to the pituitary gland to release hormones.

In vitro fertilization (IVF) is a medical procedure that allows fertilization to occur outside the body.

Triggers ovulation and supports the formation of the corpus luteum.

Meiosis is a type of cell division that reduces the chromosome number by half, producing four genetically distinct haploid cells. This process occurs in gamete-producing cells and is essential for sexual reproduction.

Mitosis is a type of cell division in which a single parent cell divides to produce two genetically identical daughter cells, each containing the same number of chromosomes as the parent cell.

Monoclonal antibodies are lab-engineered antibodies designed to bind to a specific target—in this case, hCG.

A form of estrogen that promotes the growth of the uterine lining (endometrium) and regulates FSH and LH via feedback loops.

The placenta is a temporary organ that forms during pregnancy. It connects the foetus to the uterine wall via the umbilical cord, acting as a bridge for the exchange of substances between mother and baby.

Pollination is the transfer of pollen from the anther to the stigma, a critical step preceding fertilization.

Polyspermy refers to the fertilization of an egg by more than one sperm.

A process where an initial change causes further changes that amplify the original effect, making it stronger and self-reinforcing.

Maintains the endometrium, preparing it for implantation, and inhibits FSH and LH to prevent new follicle development.