Biodiversity

Monday, May 15, 2006

DESRIPTION OF HOW PLACENTAL MAMMALS HAVE COLONIZED LAND, WATER AND AIR

The placental mammals are found to be the largest group of the mammals that comprise about 4300 (2). These types of mammals are biologically classified into nineteen orders. The largest group of these mammals contains the rodents, such as rats, mice, squirrels, and porcupines (5).

The young placental mammals are born at a comparatively advanced period (2). These mammals include elephants, whales, shrews and armadillos, it also includes pets such as dogs and cats remove the quotation marks, it includes also the farm and work animals like; cattle, sheep, and horses. The human beings also form part of the placental mammals (2).


Some of the placental mammals are found on land, water and in the air. They are found with different shapes and body size (2). They also differ in their method of surviving, some are carnivores, and some are omnivores while some are herbivores. The differences are also in those that colonized the land, they live in different shelters, for example: human live inside the house while the sheep and cattle in the kraal, etc. (2). The placental mammals that live on the land are having feet, those who occupied the water are having gills and those who colonized the air are having the wings (3). The seals, including the sea lions and the walruses does not reproduce in the open oceans, however they spend most of their time in the open oceans, and they depend on the land for reproduction (3). The largest plant eating mammals that spend their entire lives in water are dugongs and manatees (4). The only group of the placental mammals to occupy the air were the bats (2).


The whales, including the huge baleen whales and the dolphins, are well adapted as fast, open ocean predators (3). These marine placental mammals are only found in the areas where there are large amount of food, especially where the water temperature is low (3). These mammals survive the cold conditions in two different ways. Some of the placental mammals have very “sparse hair and blubber” (2). These sparse hairs help them to become warm. Other placental mammals have a double coat of fur, with very dense “under fur hairs closely packed” (2) and this prevent their skin from being wet (2).


The majority of the aquatic mammals in the world live in the ocean, yet some live in the freshwater, for example: river dolphins, and otters adapted to life in fresh water habitats. The rodents are found to have successfully occupied the land, air and the water (1). The rodents managed to occupy the air, water and the land because they are small in size and this serve as “their advantage to evade the extreme conditions” (1).


In conclusion, the placental mammals colonized the air, water and the land very successfully. The humans would not colonize the air because of lack of wings, but they colonized the land. The bats colonized the air. The seals live both the aquatic and terrestrial life, they spend most of their time in the water, but they still have to come to land so that they can reproduce.


References: [1]. Wikipedia contributors. Coordinated Universal Time [Internet]. Wikipedia. The Free Encyclopaedia, 2006 May 12, 09:00. UTC [cited 2006 May 15]. Available from: http://en.wikipedia.org/wiki/placenta.


[2]. “Mammal,” Microsoft® Encarta® Online Encyclopaedia 2006 © 1997-2006 [cited 2006 May 12, 10:00].Microsoft Corporation. Available from: http://Encarta.msn.com/encyclopedia_761561349/Mammal.html.


[3]. "Whale," Microsoft® Encarta® Online Encyclopedia 2006 © 1997-2006 [cited 2006 May 12, 1030] Microsoft Corporation. Available from: http://encarta.msn.com/encyclopedia_761565254_6/Whale.html#howtocite.


[4]. Wund, M. and P. Myers. 2005. "Chiroptera" (On-line), Animal Diversity Web. [2006May 12, 11:00]. Available from: http://animaldiversity.ummz.umich.edu/site/accounts/information/Chiroptera.html.


[5]. "Mammal," Microsoft® Encarta® Online Encyclopedia 2006 [cited 2006 May 12]. Available from:
http://encarta.msn.com/text_761561349__1/Mammal.html.

Ms Evelyn Maleka
CILLA CSIR
P.O. Box 395
Pretoria,
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Tel: (012) 841 2133
Fax: 012 842 7024.
Email: emaleka@csir.co.za
http://malekaevelyn.blogspot.com/

2 Comments:

  • This comment has been removed by a blog administrator.

    By Blogger Maleka Evelyn, at May 18, 2006 12:51 PM  

  • Hi there

    Your first reference is wrong (it leads to information about the placenta, not about placental mammals as such), especially given the occasions you cite it. Also, your grammar needs some work. But I liked the way it was structured, and it covered the subject well.

    Cheers
    Nick

    By Blogger NcK, at May 29, 2006 11:22 AM  

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