Life science

• All species or organisms, whether they are plants, animals, fungi, bacteria or protists, need to reproduce to pass their genes on to future generations
• Asexual reproduction


  The process of forming offspring without the fusion of a male and female sex cell (sperm and egg), meaning only one parent is involved
• Forms of asexual reproduction

  • Binary fission (bacteria)
  • Spore release (fungi)
  • Budding (some animals like Hydra)
  • Vegetative propagation (plants)
• Sexual reproduction


  Occurs when there is fertilization, which is when the male gamete (sex cell) fuses with a female gamete to form a zygote
• Gametes


  The sex cells used in sexual reproduction, they are haploid (contain one set of genetic information)
• Zygote


  • Contains genetic information from both parents, so is genetically different from both of them and its siblings (unless an identical twin)
• Testes


  • Male gonads located in a sac of skin called the scrotum, produce the hormone testosterone and the male gametes (sperm)
• Sperm production


  1. Produced constantly in the testes after puberty

  2. Stored in the epididymis

  3. Move to the vas deferens
• Semen production


  1. Sperm cells mixed with fluids from glands like the prostate

  2. Travels through the urethra and out of the penis
• Urethra


  Tube that carries both semen and urine out of the body, but not at the same time
• Penis


  • External male sex organ that deposits semen in the female vagina, contains spongy erectile tissue
• Ovaries


  • Female gonads that produce the female gametes (ova or eggs) and the hormones oestrogen and progesterone
• Ovulation


  An ovum (egg) is released from an ovary every month and enters the fallopian tube
• Fertilization


  1. If sperm cells are present in the fallopian tube, the egg will be fertilized

  2. The fertilized egg then travels to the uterus and implants
• Uterus


  • Sac-like organ where the embryo implants and grows during pregnancy
• Cervix


  • Band of muscles at the base of the uterus that keeps the baby in during pregnancy and dilates during labour
• Vagina


  • Tube that the penis enters during sexual intercourse and is part of the birth canal
• Puberty


  The process of physical changes through which a child's body matures into an adult body capable of sexual reproduction, initiated by hormonal signals
• Physical changes during puberty in girls

  • Maturing of vagina, uterus and ovaries
  • Ovulation starts
  • Increased release of oestrogen and progesterone
  • Hips widen, breasts develop, increase in body fat
  • Hair growth under arms and pubic area
• Physical changes during puberty in boys

  • Testes enlarge, penis enlarges
  • Increased release of testosterone
  • Increase in size of bones and muscles, become stronger and more built
  • Hair growth under arms, pubic area, face and chest
  • Voice deepens and lowers
  • Body odour changes, acne
• Emotional changes during puberty are due to changes in hormone levels and developing social relationships as the mind matures
• Menstrual cycle


  1. Every 28 days, a layer of blood-rich tissue builds up on the uterus lining

  2. Ovulation occurs, releasing an egg

  3. If egg is not fertilized, the uterus lining is discarded (menstruation)
• When is pregnancy most likely to occur?

  No answer provided
• Sperm


  The male gamete, released in millions during ejaculation, swim using their tails and enzymes to penetrate the ovum
• Ovum


  The female gamete, larger and not capable of active movement, matures and is released monthly during ovulation
• Menstruation


  1. Starts on day 1 of the menstrual cycle

  2. Ovulation occurs on day 14

  3. Average 28 day cycle
• Endometrium


  • Thickens (Oestrogen)
  • Maintained (Progesterone)
  • Menstruation
• Sperm


  The male gamete
• Sperm


  • Released by millions during ejaculation
  • Receive nourishment from semen
  • Swim by spinning tails using energy from mitochondria
  • Enzymes in acrosome dissolve outer layers of ovum
• Ovum


  The female gamete
• Ovum


  • Not capable of active movement
  • Much larger than sperm
  • Matures and is released from ovary into fallopian tube by ovulation
• Sexual intercourse and fertilization


  1. Blood pumped into penis to make it erect

  2. Penis placed into vagina

  3. Vaginal fluid lubricates movement

  4. Sperm ducts contract to move sperm

  5. Glands secrete fluid (semen)

  6. Contractions of urethra move semen through penis into vagina (ejaculation)

  7. Sperm travel through cervix, uterus and into fallopian tube to ovum

  8. Fertilization occurs
• An average ejaculation releases around 500 million sperm
• Conception and pregnancy


  1. Fertilization: sperm fuses with ovum nucleus to form zygote

  2. Zygote moves down fallopian tube, dividing and developing into morula, then blastocyst

  3. Blastocyst implants in uterine endometrium

  4. Embryo grows and develops into baby over 40 weeks

  5. Placenta and umbilical cord form to supply baby with nutrients, oxygen and remove waste
• Childbirth (labour)


  1. Dilation of cervix

  2. Expulsion: delivery of infant

  3. Delivery of placenta

  4. Detaching of umbilical cord
• Contraception


  Deliberate use of artificial methods or other techniques to prevent pregnancy
• Types of contraception


  • Male condoms
  • Female condoms
  • Birth control pills
  • Morning-after pill
• Most contraceptives are not 100% effective, but are effective more than 90% of the time
• Sexually Transmitted Infections (STIs)


  Diseases passed from one person to another through unprotected sex or genital contact
• STIs


  • Chlamydia
  • Genital herpes
  • Gonorrhoea
  • Syphilis
  • HIV