reproduction

• Fertilisation


  The process in which the nucleus of a sperm cell fuses with the nucleus of an egg cell to produce a zygote
• Zygote


  A fertilised ovum (egg cell) before it has divided into an embryo
• Gametes


  The sex cells: Sperm are male gametes, Eggs are female gametes
• Sperm cell adaptations


  • A tail to move them towards an egg cell
  • Many mitochondria to release energy for movement
  • Part of the tip of the head releases enzymes to digest the egg membrane to allow fertilisation
• Egg cell adaptations


  • The cytoplasm contains nutrients for the growth of the early embryo
  • The haploid nucleus contains genetic material for fertilisation
  • The cell membrane changes after fertilisation by a single sperm so that no more sperm can enter
• Fertilisation


  1. Nucleus of sperm fuses with nucleus of egg

  2. Produces a zygote
• Zygote development


  1. Divides by mitosis into a ball of genetically identical cells called the embryo

  2. Embryo attaches to uterus lining and develops into a fetus
• Fetus development


  • Needs protection, oxygen, nutrients, waste removal
  • Protected by uterus and amniotic fluid
• Placenta


  • An organ that grows into the wall of the uterus and is joined to the fetus by the umbilical cord
  • Allows exchange of materials like oxygen, nutrients, and waste between fetus and mother via diffusion
• Humans typically reproduce by sexual fertilisation, producing genetically unique offspring
• Gametes


  Male and female sex cells
• Ova


  Female gametes
• Sperm


  Male gametes
• Fertilisation


  A male and female gamete join together
• Gametes


  • Specialised cells with adaptations to increase chances of fertilisation and successful development of a baby
• Testes


  Produce millions of sperm and male sex hormones
• Scrotum


  Bag of skin that contains the testes
• Ejaculation


  Sperm pass through sperm ducts and mix with fluids to create semen, which exits the body through the penis
• Ovaries


  Contain undeveloped eggs and produce female sex hormones
• Oviducts


  Tubes that connect the ovaries to the uterus
• Uterus


  Muscular bag where a baby develops until birth
• Cervix


  Ring of muscle at the lower end of the uterus that keeps the baby in place during pregnancy
• Vagina


  Muscular tube that leads from the cervix to the outside of the body
• Gestation


  Time period of around 40 weeks for a fetus to develop in the uterus
• Fetus


  Unborn baby
• Placenta


  Organ that provides oxygen and nutrients, and removes waste substances, for the fetus
• Umbilical cord


  Joins the fetus to the placenta
• Mother's blood and fetus's blood

  Do not mix, but substances diffuse across the placenta
• Drugs, alcohol, and smoking during pregnancy can affect the fetus and increase health risks
• Birth


  Cervix relaxes, uterus contracts to push the baby out through the vagina
• Caesarean section


  Surgical method of delivering a baby when a vaginal birth is not possible