Sexual Reproduction

• Sexual reproduction: A type of reproduction in which offspring are created by combining genetic information from two individuals
• ANIMALS - Advantages of internal fertilisation

  • More likely successful fertilisation
  • Embryo protected from predators
  • Offspring more likely to survive
• ANIMALS - Disadvantages of internal fertilisation

  • Higher energy to find a mate
  • Less offspring produced
  • More energy required to raise and care for young
• ANIMALS - Advantages of external fertilisation

  • Little energy required to mate
  • Large number of offspring produced
  • Offspring can spread widely = less competition
• ANIMALS - Disadvantages of external fertilisation

  • Many gametes go unfertilised
  • Offspring not protected by parents
  • Survival rates are lower
• Internal fertilisation in animals

  • Takes place inside the body of the female 
  • Involves male attraction and copulation (P in V)
  • Requires 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 in animals

  • 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