Reproduction

Male Reproductive System

Structures and functions:

• Testes (in scrotum): produce sperm (by meiosis) and testosterone
• Epididymis: stores and matures sperm
• Vas deferens: tube carrying sperm from epididymis to urethra
• Seminal vesicle: produces fructose-rich fluid to nourish sperm
• Prostate gland: produces alkaline fluid to neutralise vaginal acidity
• Urethra: shared tube for urine and semen
• Penis: delivers sperm during intercourse. Glans: head of penis. Foreskin: covering of glans

Female Reproductive System

• Ovaries: produce eggs (by meiosis) and hormones (oestrogen, progesterone)
• Fallopian tubes (oviducts): where fertilisation occurs; transport egg to uterus via cilia and peristalsis
• Uterus: muscular organ where the embryo implants and develops. Lined by the endometrium
• Cervix: narrow opening between uterus and vagina
• Vagina: birth canal and receives sperm
• Vulva: external genitalia. Labia: protective folds. Clitoris: sensory organ

The Menstrual Cycle (28 days)

1. Menstruation (days 1–5): uterus lining (endometrium) breaks down and is shed
2. Follicular phase (days 1–13): FSH from pituitary stimulates follicle development in ovary. The growing follicle produces oestrogen, which rebuilds the endometrium
3. Ovulation (day 14): surge of LH triggers release of a mature egg from the Graafian follicle
4. Luteal phase (days 15–28): the empty follicle becomes the corpus luteum, which produces progesterone to maintain the endometrium. If no fertilisation → corpus luteum degenerates → progesterone drops → menstruation begins

Pregnancy

Fertilisation → zygote → morula (ball of cells) → blastocyst (hollow ball, implants in endometrium ~day 7) → germ layers form → embryo (weeks 3–8) → foetus (week 9 to birth)

The placenta forms to allow exchange of O₂, nutrients, and waste between mother and foetus. It also produces hormones (progesterone, oestrogen) to maintain pregnancy.

Labour and birth: Oxytocin from pituitary stimulates uterine contractions. Positive feedback loop intensifies contractions until delivery.

Hormonal Control of Reproduction

Hormone	Source	Role
FSH	Pituitary	Stimulates follicle development (female) and sperm production (male)
LH	Pituitary	Triggers ovulation; stimulates corpus luteum
Oestrogen	Ovaries	Rebuilds endometrium; female secondary characteristics
Progesterone	Corpus luteum/placenta	Maintains endometrium; supports pregnancy
Testosterone	Testes	Sperm production; male secondary characteristics
Oxytocin	Pituitary	Stimulates uterine contractions during labour
Prolactin	Pituitary	Stimulates milk production (lactation)

Contraception & Fertility

Contraception methods:

• Natural: rhythm method, withdrawal (less reliable)
• Mechanical: condoms, diaphragm, IUD
• Chemical: contraceptive pill (oestrogen + progesterone prevents ovulation), morning-after pill
• Surgical: vasectomy (males), tubal ligation (females)

Infertility treatments: stimulating ovulation (fertility drugs), artificial insemination (AI), in vitro fertilisation (IVF), intracytoplasmic sperm injection (ICSI), egg freezing.

Screening: antenatal screening (ultrasound, blood tests), genetic screening (e.g. for Down syndrome), postnatal screening (e.g. heel prick test for PKU).

Flower Structure

Flowers contain the reproductive organs of flowering plants:

Part	Function
Sepals	Protect the flower bud before it opens
Petals	Attract pollinators (insects) - often brightly coloured
Stamen (male)	Anther produces pollen; filament supports the anther
Carpel (female)	Stigma receives pollen; style connects to ovary containing ovules
Receptacle	Base of flower that supports all parts

Pollination

Transfer of pollen from anther to stigma.

Feature	Insect-Pollinated	Wind-Pollinated
Petals	Large, colourful, scented	Small, dull, no scent
Nectar	Present (attracts insects)	Absent
Pollen	Sticky, spiky (adheres to insects)	Lightweight, smooth, abundant
Stigma	Sticky, inside flower	Feathery, hangs outside (catches wind-blown pollen)
Anthers	Inside flower	Dangling outside (pollen disperses in wind)

Seed Structure

• Testa: tough outer seed coat - protects embryo
• Embryo: the young plant, consisting of:
  • Radicle: embryonic root (first to emerge during germination)
  • Plumule: embryonic shoot (grows upward toward light)
• Endosperm: food store for the developing embryo

Seeds produce growth regulators that stimulate growth of fruit tissues around them.

Fruit & Seed Dispersal

Seeds/fruits must be dispersed away from the parent plant to reduce competition:

• Wind: light seeds with wings/parachutes (e.g. dandelion, sycamore)
• Water: waterproof shells, air pockets for buoyancy (e.g. coconut)
• Animal (external): hooks or burrs that attach to fur (e.g. burdock)
• Animal (internal): fleshy fruits eaten, seeds pass through digestive system (e.g. blackberry)