Biodiversity

Friday, May 12, 2006

ADAPTATION REQUIRED TO MAKE THE TRANSITION FROM AN AQUATIC TO A TERRESTRIAL ENVIRONMENT- AMPHIBIANS

ADAPTATION REQUIRED TO MAKE THE TRANSITION FROM AN AQUATIC TO A TERRESTRIAL ENVIRONMENT- AMPHIBIANS

In general Amphibians (e.g. Frogs) live in both water and on land, but they spend most of their time in water. It is indicated that the amphibians are soft bodied animals and they are hunted by predator such as big fish (2). Amphibians such as the common European Toad (Bufo bufo) protect itself from predators by “inflating its body and stands on its toes to so that it can appear as large as possible” (2). Species such as the Bellied toad produces a poisonous mucous to protect itself against predators. The mucous is liquid substances, which is believed to have a bitter taste to predators and it is also poisonous (2). I believe that the mucous play a role as a defence mechanism against predation of Bellied toad. But, this mucous does not serve any purpose because the preditor will die after eating it. Strange enough is that hunters use this mucous substance to tip their arrows especially during hunting (2) and also function as a body lotion by keeping the skin moist (2).

When amphibians are in water they use gills to breath but when on land the gills are replaced by other respiratory organs i.e. lungs. It appears that the “amphibians change their skin by developing glands in order to avoid dehydration”. Amphibians’ eyes develop eyelids and that enables them to see on the land. Amphibians’ eardrum locks the middle ear while on land (2). Amphibians change most of their physical structures in order to survive while on land.

Limitations to an amphibian to terrestrial life

Amphibians are partly successful in their “colonization of land, since their limbs are short and they need to bend their body in order to take reasonable strides" (1). Amphibians skin is permeable but, in dry atmospheres they loss water quickly which will lead to dehydration (1). Amphibians do not have the mechanisms to drink water while they are on land and once they are dehydrated they die. Their skin need to be moist always in order to assist the respiration processes since their lungs are not really made for breathing. They only use their lungs only while they are on land. These limitations restrict amphibians to spend most of their time in moist environments (in water) (1).

In dry habitats, amphibians’ development is limited by the availability of moisture (amount of water) on land not by temperature (6). For example Breviceps which live in dry regions only come out (of burrows) above the ground during heavy rainfalls (6). Adults Breviceps come out from their underground burrows and absorb rainwater through their skins, thus refilling their body fluids (6). Some frogs are able to hold water; and minimize their dependence on water under dry conditions. When it rains they absorb lots of water and then return to their burrows. When they are in their burrows they prevent the water loss through their skin by secreting a membrane around themselves (6).

Many frogs are able to absorb water directly through the skin, especially around the pelvic area. However, the permeability of a frog's skin can also result in water loss. Some tree frogs reduce water loss with a waterproof layer of their skin. Others have adapted behaviours that conserve water, including engaging in nocturnal activity and resting in a water-conserving position. Amphibians are limited by the amount of water available on land because on land there is lack of water and also the permeability of the skin. They are susceptible to pollution because their skins absorb everything and their blood is contaminated easily since what they absorb through their skin goes directly to the blood. It is difficult for amphibians to survive on land for a long time they can only survive for just a short time.

References:

1. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 Mar 27, 22:44. UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Permeable
2. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 00:20. UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Amphibians
3. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 02:38. UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Frog
4. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 30, 18:42. UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Nocturnal
5. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 03:32. UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Microhylidae
6. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 Feb 8, 17:35. UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Midwife_toad
7. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 02:38. UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Anurans

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

3 Comments:

  • Again, this is just a collection of extensive quotes. Even worse, though, is the fact that many of your quotes are unattributed! Technically, this may not be plagiarism, but it's close enough...

    Nick

    By Blogger NcK, at May 18, 2006 9:08 AM  

  • fixed

    By Blogger lethabo, at May 23, 2006 9:05 AM  

  • No, I'm afraid you haven't fixed it. You've just removed the quotation marks in some cases, making it an even bigger case of plagiarism. I'm sorry if my previous comments confused you further, but plagiarism is still plagiarism...

    Nick

    By Blogger NcK, at May 29, 2006 3:55 PM  

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