Fertilisation

• Internal fertilisation

  • Takes place inside the body of the female
  • Involves male attraction and copulation
  • These require energy investment
  • Put the organism at risk of predation
  • Fewer eggs overall need to be produced
  • Occurs in some invertebrates (insects, snails) and most vertebrates (reptiles mammals and birds)
  • A smaller number of gametes and offspring than in external fertilisation due to:
  • A higher chance of fertilisation (more direct sperm to eggs)
  • A higher success rate of survival of young
  • Parental care of eggs and or young is more common
• External fertilisation

  • Takes place in the external environment
  • Environment needs to be aquatic or moist terrestrial to prevent dehydration of gametes and allow gamete mobility
  • Involves a simultaneous release of gametes
  • Occurs in most invertebrates and some invertebrates (fish and amphibians)
  • A higher number of gametes and offspring than internal fertilisation due to:
  • A lower chance of fertilisation (less direct)
  • A lower survival rate of zygotes and offspring
  • Usually no parental care
• Gametogenesis


  Production of gametes
• Oogenesis


  • Process of female gametes (eggs) production in animals
• Spermatogenesis


  • Process of male gametes (sperm) production in animals
• Oogenesis


  • Oogonium
  • Primary oocyte
  • Secondary oocyte
  • Egg and 3 polar bodies
• Oogenesis


  1. Primary oocyte forms from a diploid cell

  2. Meiosis I forms a secondary oocyte and a primary polar body

  3. Meiosis II in the secondary oocyte produces an egg and polar body
• Polar body


  Small cell produced by the division of an oocyte that is not capable of developing into a viable organism
• The egg survives, while all the polar bodies die
• Only one functional egg cell comes from this process
• Spermatogenesis


  • Occurs inside the walls of the seminiferous tubules within the testes
  • Mature sperm are released into lumen of seminiferous tubules
• Gametogenesis


  Production of gametes
• Oogenesis


  • Process of female gametes (eggs) production in animals
• Spermatogenesis


  • Process of male gametes (sperm) production in animals
• Oogenesis

  • Oogonium
  • Primary oocyte
  • Secondary oocyte
  • Egg
• Oogenesis

  1. Primary oocyte forms from a diploid cell

  2. Meiosis I forms a secondary oocyte and a primary polar body

  3. Meiosis II in the secondary oocyte produces an egg and polar body
• Polar body


  Small cell produced by the division of an oocyte that is not capable of developing into a viable organism
• The egg survives, while all the polar bodies die
• Only one functional egg cell comes from this process
• Spermatogenesis


  • Occurs inside the walls of the seminiferous tubules within the testes
  • Mature sperm are released into lumen of seminiferous tubules
• Oogenesis


  Process of female gametes (ova) production in animals
• Begins at


  Menarche
• Ends at


  Menopause
• Females are born with all the eggs they will produce as primary (immature) oocytes
• Oogenesis

  1. Begins before birth

  2. From a primary oocyte - meiosis I forms a secondary oocyte and a primary polar body

  3. Meiosis II in the secondary oocyte produces an egg and polar body
• Primary oocyte

  Cell that forms one primary oocyte after growth and development
• Secondary oocyte

  Cell that forms after meiosis I in the primary oocyte
• Polar body


  Cells that die after meiosis II in the secondary oocyte
• Only one functional egg cell comes from this process
• Implantation

  If a fertilised ovum implants into the uterine wall, pregnancy results and is maintained by secretion of various hormones
• Implantation occurs

  ~7 days after fertilisation
• Hormonal control

  Endocrine glands regulate and control the menstrual cycle in a coordinated manner, it synchronises the ovarian and uterine cycles to ensure fertility
• The result is an increase in the probability of successful reproduction, biological fitness, and therefore, the continuity of species
• Ovarian cycle


  The decrease and change in the ovary during which the follicle matures, the ovum is shed, and the corpus luteum develops
• Uterine cycle


  The changes in the uterus, requires for the prep of the uterus for pregnancy
• Pregnancy
• Birth