Biodiversity

Friday, May 12, 2006

COMPARISON OF MODE OF REPRODUCTION BETWEEN THE PLACENTAL MAMMALS AND MARSUPIALS

Placental mammals are vertebrate animals that have placenta that join the growing embroy inside the womb of the mother and marsupials are invetebrate mammals. There are differences between "the marsupials and placental mammals during the process of gastation" (2,3) in which the babies grow inside the body of their mother before they born. This placental give the species away of feed fetus and during this process it will also reach maturity during the birth.


The rate of gestation between marsupial and placental mammals is not the same. In marsupials, their reproduction is more difficult compared to the placental mammals. "Embryo becomes a new organism during the process of the fertilization and auto immune system from their mother will assault it. The amniotic membrane work together with the mother inorder to protect them not to be assaulted" (2,3).

The marsupial mammals give birth at short period and placental mammals give birth at long period. The short gestation qualified to the development of the yolk type reproduction. The longer gestation in marsupials qualified to the fully developed off spring. Marsupials and placental mammals also differ during their birth" (1). The birth rate in marsupials occurs at "the early stage and they carries their baby in the puch" (2). It takes a week or a mouth for unborn organism to pouch and attached to a teat depending on that particular species. In placental mammals, the birth rate occurs at late stage and this can cause the process of gestation develop fully during the orocess of off spring.

The other differences between placental and marsupial’s reproduction occurs in the mode reproduction and any pattern. The pregnancy in marsupials do not disturd the development of the oestrus cycle and placental disturb the development of the oestrus cycle" (1,2,3). The reproduction in marsupials it said to be full developed and there is no combination in both right and left of marsupial’s vaginae to from a single body through psyeodoraraginal canal"(3).


In marsupials "the right and left uterus complex compared to in placental" (2,3) . During the embryo in marsupials mammals the process of development female reproductive tract is different compared to the one which is found in the placental mammals. In marsupial, the marsupiums develop in females in order to look after the babies and they also have two reproductive. The male marsupials have "two penis and their scrotum is found in the front part of the penis" (3). In placental mammals "the scrotum is found at the end of the penis" (3).


The placental mammals have long period of gestation and this will cause a full development of the off spring. The maturation of placental allows nutrients to move from the mother's system to the embryo and waste to be carried away. The placenta is made by layers which also provide blood to it.

Reference:

1. Roach, J. 2002. Earliest known ancestor of placental mammals discovered. [Online]. Available from: http://news.nationalgeographic.com/news/2002/04/0423_020425_firstmammal.html [24 April 2002, 15:45]

2. Wikipedia contributors. Placental [Internet]. Wikipedia, the free encyclopaedia, 2006 May 07, 18:21 UTC [Cited 2006 May 12, 10:21]. Available from:
http://en.wikipedia.org/wiki/Placental

3. Wikipedia contributors. Marsupials [Internet]. Wkipedia, the free encyclopaedia, 2006 May 09, 17:16 UTC [Cited 2006 May 12, 11:10]. Available from: http://en.wikipedia.org/wiki/Marsupials

4. Wund, M. and P. Myers. 2006. "Metatheria" (On-line), Animal Diversity Web. Accessed May 24, 2006 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Metatheria.html.


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com/

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