Biodiversity

Friday, May 12, 2006

COMPARISON BETWEEN THE PLACENTAL AND MARSUPIALS MODES OF REPRODUCTION

There are huge differences between the marsupials and placental mammals. The different between marsupials and placental mammals is the mode of reproduction and gestation period. They are also differs in gestation period. Marsupials have very short gestation whereas the placental have usually longer gestation. "The neonate are incompletely developed in marsupials where as neonate are anatomically complete in the placental. In addition, the reproductive tracts of marsupials in the females are fully doubled. Nevertheless, the right and left vagina do not combine to form a single body as they do in placental mammals"(2)Thus, in the marsupial’s mammals, birth takes place through new canal, that is pseudovaginal canal. http://www.nwcreation.net/marsupials.html

"The longer gestation period that in the placental mammals are occurs in the offspring that are born, and fully developed. One can say that, the mature time in placenta compared to other vertebrates it depends on placenta, which allows nutrients to move from mother system to embryo"http://www.nwcreation.net/wiki/index.php?title=Main_Page. "The mother and embryo do not share the same blood supply, but the placenta is richly supplied with blood vessels, nutrients metabolites pass through and prevent the transfer of immunity system"(3). In Marsupials pregnacy does not break the continuance of the next oestrus cycle, because it is not in the placenta.

However birth in marsupials occurs much earlier as opposed to the placenta mammals. The fetus to the pouch becomes attached to teat just for a weeks or a months. This depends on the type of species, but marsupials spend 12 days in the reproductive tract(1)". http://www.nwcreation.net/wiki/index.php?title=Main_Page

“Marsupials and placental birth may not equal. Gestation length indicates the direct exchange between advantageous for child as is not like to the mothers. Marsupials’ reproduction is more beneficial, by reducing the death especially related to child mother union. The length and time of marsupials’ gestation are important through the evolutionary genetic recombination. The young placenta mammals spend long time to develop inside the mother body before birth.”(2)


The development of marsupial embryo, the arrangement of ducts that become the female reproductive tract differs from the placental. The placental mammals have penis, which look like the female vagina, whereas the marsupial’s males have a forked, and scrotum penis in the front. As for instance, wolf animals have many marsupials that are essentially identicall to the placental mammals. “Marsupial and placental mammals have evolved coincidently as a results of common environmental exposures”(2). The hands indicates that, each marsupial is unique kind from their placental twin. http://www.pbs.org/wgbh/evolution/library/01/4/pdf/l_014_02.pdf

Just to conclude, marsupials birth takes place through a median canal. Its marsupium is used for nursing young, but this, does not happen in all the marsupials species. On the other hand, the placental species has no marsupium. Some marsupials have chorioallantoic placenta, with no villi, while in the placenta have extensitve villi. Left and right vaginae and uteri of marsupials do not fused to form a single body, where as left and right vaginae of placental is fused. Penis in placenta is not forked, scrotum lies in the posterior of the penis. According to the degree and development of young in placental, gestation period is long and the young are born with functional organs and have short lactation period where as in the placental mammals lactation period is prolonged . In marsupials degree of development the young have short gestation, which can takes 8 to 43 days depending on species. Development takes place in pouch(1).

References

1. Wikipedia Contributors. Coordinated universal time. Marsupials evolution[Internet]. Wikipidia, The free encyclopedia; 2006 May, 10, 04:55 UTC [cited-2006 May, 12]. Availabe from:
http://www.nwcreation.net/wiki/index.php?title=Main_Page

2. Andriene, L. 2001. The Human Evolution Coloring Book [Internet] [Cited 2006 May, 12]. Available from:
http://www.pbs.org/wgbh/evolution/library/01/4/pdf/l_014_02.pdf

3. Northwest creation Network, Marsupials Evolution and post flood migration [Internet] [Cited 2006 May, 12] Avalable from:
http://www.nwcreation.net/marsupials.html

Linette Netshiheni
CSIR
Pretoria
0001
Cell: 0820446442
Tell: 012 841 2133
Fax: 012 842 3676
tnetshiheni@csir.co.za
Weblog: http://tnetshiheni-linette.blogspot.com/

1 Comments:

  • You have not always used quotes to indicate copying more than four words verbatim from a reference. This is plagiarism.

    By Blogger Gwen, at May 25, 2006 4:07 PM  

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