Biodiversity

Friday, May 12, 2006

COMPARISON BETWEEN THE PLACENTAL AND MARSUPIAL MODES OF REPRODUCTION

Marsupials are mammals such as Kangaroos. The name marsupial originate from the fact that the female marsupials has a pouch “bag” which is used to carry its young during early childhood (1). Marsupial females have two vaginas and males have two penises for reproduction unlike the placental where the males have one penis and the females have one vagina. The two vaginas of marsupials have only one opening which leads to the outside (1). The two penises are only used to pass sperms unlike in the placental where the penis is used to pass both the sperm and urine (1).

Placental mammals are mammals such as humans. A placenta is an organ which is only present when a female placental is pregnant or during gestation (2). The fetus (baby) inside the placenta is attached to the wall of the uterus. When the fetus is in placenta it receives nutrients and oxygen from the mother. Whatever the mother eats the fetus also eats so if the mother is not eating nutritious food the fetus is also starved of the nutrients (2). The placental membrane or barrier protects the fetus against some harmful substances which can harm the fetus (2). Some substances such as alcohol can penetrate the membrane; harm the baby and the baby could end up suffering from fetal alcohol syndrome (2).

Marsupial females have a yolk sac when they are pregnant. The fetus gets its nutrients from the yolk sac (1). The baby in the placental mammals gets all the nutrients from the mother but through the umbilical cord (3). The marsupials give birth early than the placental mammals. They carry the baby for a month in their stomachs while the placental mammals carry their babies for nine to ten months. Marsupial baby develop fully when they are in their mothers pouch where there are nipples (1). When the baby has developed it can leave its mothers pouch to go play and when they are through the baby return to its mother pouch for warmth (1). Placental mammals’ baby develops in the mothers’ womb until it is fully developed (2).

Placental mammals differ from the marsupial mammals in the way they reproduce. Placental mammals develop a complex placenta to protect the fetus from the mothers’ immune system while the marsupials do not have to develop a complex placenta (1). Marsupials give birth earlier than placental mammals; they do not have to carry a large fetus to full-term. The placental mammals (e.g. humans) carry their babies in the womb for nine months but the marsupial mammals (e.g. Kangaroos) carry their babies in the worm for a month (“thirty-one to thirty six days") (4). If a placental mammal gives birth early before the baby has fully developed (prematurely). Then the placental mother is going to take care of the baby the same way as the marsupials. The mother is going to use a blanket and put the baby inside the blanket on the mothers’ stomach. The blanket act like a pouch in the marsupials and the method that humans use is called the Kangaroo care. Marsupials and mammals take care of their offsprings but in different ways.
Reference:

1. Wikipedia contributors. Marsupials [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 17:16. UTC [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Marsupials
2. Wikipedia contributors. Placenta [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 7, 18:21. UTC [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Placenta
3. Wikipedia contributors. Umbilical cord [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 8, 18:02. UTC [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Umbilical_cord
4. Wikipedia contributors. Kangaroo [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 11, 10:30. UTC [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Kangaroo

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
Mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

1 Comments:

  • In your last paragraph, you copied some phrases (five or more words and more than once) from the marsupial article in Wikipedia without using quotes. This is plagiarism.

    Keep to one subject in an essay. Kangaroo care of premature babies is interesting but not relevant to the topic.

    By Blogger Gwen, at May 26, 2006 10:32 AM  

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