Introduction to Reproduction


Key Terms

Spermatogenesis sperm production

Oogenesis egg production

Insemination the sperm entering the female

Implantation the egg connecting to the uterus lining

Gestation pregnancy

Parturition giving birth

Lactation producing milk 

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Delayed Implantation

Facultative Diapause this is a mechanism that is associated with metabolic stress (lactation). If a female becomes pregnant while still lactating for her original youngster, the suckling stimulus will cause the embryos to enter diapause.

Obligate Diapause this is a mechanism to allow mammals to time the birth of their youngsters with favourable environmental conditions 

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Lay eggs which develop and hatch outside the body. The young inside develops using the nourishment from the yolk.


  • easier to hide
  • lots of young
  • less likely the mum will die
  • might not need parental care
  • no lack of mobility 


  • eggs are vulnerable
  • mums can become egg bound
  • low success rate
  • can't tell if they're fertilised 
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Producing young with eggs that hatch inside the body. The category includes certain types of fish, reptiles and invertebrates. 


  • young are alive
  • mother doesn't have to give nourishment
  • can still have a lot of young
  • nutrients can be reabsorbed 
  • the egg is safer


  • easier to see because of the movement
  • still have to carry them around for a period
  • more complicated
  • if the parent dies, the young will most likely die
  • less young than oviparous
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Give birth to live young. The young gain nourishment from the mother's blood via the placenta.


  • fully developed
  • protected in the parent
  • warm environment


  • Mum is slowed down
  • needs nourishment from the mum constantly
  • complications because of a larger baby
  • relies on mother after birth
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A mammal that lays eggs, usually have a cloaca. Monotremes have pores in their armpits for milk production


  • able to provide milk
  • can leave young in the nest


  • in the nest for a long period
  • need yolk and milk production
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Give birth to partially developed young and the young then develop inside a pouch. Females have two vaginas (both open via the same external orifice but enter different parts of the uterus). Males have a prolonged penis and testicles are situated in front of the penis.


  • protection from predators
  • no complications at birth
  • short pregnancy
  • can have offspring at different stages (for example, Kangaroos can have one joey in the womb, one new-born joey in the pouch and one larger joey outside the pouch)


  • long aftercare
  • very vulnerable
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