Lethabo

im 22 years old, female doing my honns in ecological informatics at csir(pretoria)

Name:
Location: pretoria, gauteng, South Africa

i completed my Bsc (microbiology physiology) degree in 2005 at University of Limpopo, now im doing my honns in ecological informatics at university of the western cape.

Tuesday, May 16, 2006

WHY REPTILES ARE BETTER ADAPTED TO A TERRESTRIAL ENVIRONMENT THAN AMPIBIANS

Reptiles are cold blooded animals (ectothermic). Their cellular metabolism produces some heat but reptiles do not generate enough to maintain a constant body temperature (1). Reptiles rely on gathering and losing heat from the environment to regulate their internal temperature, for example they move between sun and shade. They also move warmed blood into their body core, while pushing cool blood to the periphery. In their natural habitats, most species are adapted to the mechanism and they can maintain their core body temperatures within a fairly narrow range. While this lack of adequate internal heating imposes costs relative to temperature regulation through behaviour, it also provides a large benefit by allowing reptiles to survive on much less food. While warm-blooded animals move faster in general, an attacking lizard, snake or crocodile moves very quickly.

Lizards the Scincomorpha family, which include skinks, often have shiny, iridescent scales that appear moist. However, like all other lizards, they are dry-skinned and generally prefer to avoid water. All lizards are able to swim if needed, however, and a few are comfortable in aquatic environments (2). For example marine iguana (a lizard which live in the water) when it is cold it is unable to move effectively, which is makes it more vulnerable to predators. Marine iguanas are very aggressive before they have warmed up since they are unable to run away (3).

The physiology of frogs is generally like that of other amphibians but differs from other terrestrial vertebrates (5) because oxygen may pass through their highly permeable skin and reptiles uses their nostrils. This unique feature allows frogs to "breathe" largely through their skin. Because the oxygen is dissolved in an aqueous film on the skin and passes from there to the blood, the skin must remain moist at all times; this makes frogs susceptible to many toxins in the environment, some of which can similarly dissolve in the layer of water and be passed into their bloodstream (4). Reptiles skin mostly consists of scale and it is not permeable. There is a lack of moisture on land so in order for amphibians to survive they require a lot of mosture unlike the reptiples. Ampibians depend mostly on the amount of mosture available unlike the reptiles.

Many frogs are able to absorb water directly through the skin, especially around the pelvic area which makes it more vulnerable to absorb a lot of poisonous gases from the atmosphere. The permeability of the skin of a frog can also result in water loss especially on land unlike the reptiles (3). The skin of reptiles acts as a structure for protective features e.g. scales (5).

Amphibians and reptiles are both ectothermic- can not maintain their body temperature- they maintain their body temperature by basking on the sun. They absorb a lot of heat so that they can be active. The problem is amphibians can not survive on land for long periods unlike the reptiles which basically live on land. When the amphibians are on land their skin loses a lot of water since they spend most of their time in water. When amphibians are on land mostly they absorb a lot of heat within a short period of time so that by the time they dry out they should have collected enough heat and they also minimize the period of lethargy after emerging from the water. Reptiles can maintain and retain their water inside unlike some amphibians.

Reference:

1. Wikipedia contributors. Reptiles [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 10, 02:57. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Reptiles
2. Wikipedia contributors. Lizards [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 10, 07:12. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Lizard
3. Wikipedia contributors. Anura [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 10, 02:38. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Anura
4. Wikipedia contributors. Marine Iguana [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 8, 23:48. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Marine_Iguana
5. Wikipedia contributors. Vertebrate [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 7, 13:12. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Vertebrate

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

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