Lecture 24

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Lecture 24
2013-11-16 23:05:29

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  1. What are three different groups of mammals breeding style
  2. Monotremes reproduction
    • Lay eggs
    • feed babies through lactation pores
    • Platypus: 1-3 eggs no pouch lactation 3-4 months 
    • Echidna : 1 egg hatch 14 days after laying 6- 7 months lactation
  3. Platypus mating
    • When the breeding season begins, an
    • increase in male testosterone is seen. This results in higher levels of male
    • aggression towards other males often, involving the use of venomous spurs
    • towards other males (Ladiges, Gleadow & Handasyde) 2013.This behaviour is
    • primarily used to assert dominance over other male platypuses and discourage rivals
    • in order to increase chances of finding a suitable female to mate with.(Whittington,
    • C.M. et al 2008)As this behaviour occurs during the
    • breeding season of platypuses, it would most likely occur during the during the
    • months of July to October
  4. Describe marsupials
    • gestation short can vary from 4 - 46 days
    • supernumary observed 
    • Antechinus: synchorised mating where male mates so much he dies
  5. Lactation in marsupials
    • Their lactation is different to eutherians
    • early development young is fed dilute milk that is rich in carbs and the young suckles continuously 
    • Late deveopment : intermittent suckling concentrated milk rich in proteins and fats
  6. What is embryonic diapause
    • After giving birth to a young, female mates within a day but the blastocyst in stopped at this stage. this is due to suckling stimulus due to joey
    • thus 3 children can be with mum at once
  7. Describe eutherian reproduction
    • Long gestation
    • short lactation 
    • milk composition relatively constant 
    • Bats : only have 1-2  live young ,8 months in gestation , gives birth upside down , can recognize its offspring among millions of others in nursery
  8. Is marsupial birth primitive ?
  9. Although placental birth has several advantages, marsupial birth does bear some
    • benefits
    • Marsupial births in particular circumstances of stress can be more beneficial in reducing death levels. Often in Eutherians, if the mother dies then the child will die as well.However in the case where a marsupial mother dies , a pouched baby may have a chance to survive
    • If conditions change or she runs out of food, the marsupial mother can easily terminate an external pregnancy, this is not possible in eutherians births. Furthermore the larger the baby the more difficult it is for the mother to deliver it. Breech positions and complications
    • during the birthing process are eliminated in marsupial births. Thus during severe environmental stress giving birth earlier becomes more beneficial for the success of the population and hence marsupial birth might be naturally selected