REASON WHY PLACENTAL MAMMALS HAVE COLONIZED LAND, WATER AND AIR

Placental mammals are considered the largest group of mammal species. They are class of vertebrates animals, which is characterised by mammary glands. In females it produces milk to nourish their offspring .most of the placental mammal are warm blooded animal and they also have fur (hair) which they use to protect their skin agaist cold. fur helps to insulate,while the warm-blooded part helps to regulate body tempareture . Having fur and warm- blooded bodies enables them to adapt various environment. placental mammal includes species such as elephant, whales, bats and farm as well as work animals. Also human are regarded as placental mammal.[1]

Placental animal have colonise all the environment land, water, and air. Because of their bodies that can regulate the tempareture and also the modification that they underwent during environmental change which influence other species to adapt different environmental condition. some mammals adapt terrestrial environment as the cannot cope climate in the sea, while other adapt aquatic environment because they cannot move on land. They also adapt different enviroment because of the abundant feed that this different environment provide.

For example;whales was suggested living at the edge of the water in terrestrial,they get into water when they find that water is rich source of food. And inside the water there is no competition of foods .they tend to adapt aquatic style and this results in the modification of their bodies. Because they where living in the new environment and eating different food some change the structure of teeth so that they can eat their prey easily.[2]

This can indicate that during evolution and adaptation of placental mammals to colonise different environment, they underwent modification on their bodies. Some modification cause problems when they move to land, “they have to develop water proof external layers, internal gas exchange systems and ways of reproducing that did not evolve water “.[3] Some develops strong support systems endoskeletons and exoskeleton that will enable them to move on land. But not all placental mammals have managed to solve the problem of moving to land, they then adapt to their origin habitant which is the aquatic environment. [3]

It was suggested by paleothropologist that evolution of most species including placental mammals evolve from aquatic environment, it can be suggested that those mammals that are still occupying aquatic environment is because they fail to meet the modification that allows them to walk on land or on air. It was a benefit for placental mammal to have lighter bodies and strong legs that can suport them against gravitational force that found on land. and also to have bodies that can retain water, so some develop waxy and water proof cuticle which is useful to conserve water in the body.[3]

The adaptation of different mode of locomotion also help the placental mammal to colonise most environment. those mammal that adapt quadrapedal find it easy to live on land ,and those that develops wing like birds(bat) they colonise air simple,while those that fail they retain their fins and develop support that can allow them to move around outside water but mostly find themselves in the water as they can not adapt for a period on land.[1]

Some Placental mammals colonize land and water forduring reproduction period as they cannot produce in the aquatic environment , mammals such as sea lions they give birth outside water.so this indicate that having body that can regulate body tempareture it became easy for the species to colonize many environment, if the climate is not favouring them they can regulate it to favour them inside their body.[2]

In nutshell placental mammals have a better chance to colonize vast environment because they are warm-blooded animals that can regulate their body temperature and they have underwent modification on mode of locomotion that helps them to adapt many habitants.when they adapt to diferent environment the end up choosing diet which tend to enhance their metabolic rate which increase the regulation of tempareture. When they move out of water they develop body structure which is endoskeleton which support endothermic the process that control body tempareture.thats why it is simple for placental mammal to adapt variety of environment.

Reference:

1. Hastings.L. Mammal Adaptation.[Internet] [cited 2006-May-11]Available from: http://animals.about.com/cs/mammals/a/mam101ab.htm

2. David Burnie ,B.S.Mammal, [internet] Microsoft® Encarta® Online Encyclopedia 2006 [cited 2006 may 8]. Available from:http://encarta.msn.com/encyclopedia_761561349/Mammal.html

3. Evolution for Teaching. Plant and Animal Evolution; [Internet] University of Waikato. [Cited 2006 May 08]Available from: http://sci.waikato.ac.nz/evolution/AnimalEvolution.shtml

Mr Elelwani Muanalo
NISL- Ecological Informatics Student
CSIR Pretoria
Tel: +27 12 841 2133
Fax: +27 12 842 7024.
Email: emuanalo@csir.co.za
My bloger URL: http://muanalo.blogspot.com/