The Biology and Diversity of Extant Reptiles

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The Biology and Diversity of Extant Reptiles

The word reptile itself does not describe a monophyletic group of

vertebrates, like the mammals or birds. It is used to classify a

polyphyletic group of animals that are a subset of the larger group of

Amniotes. The term is best described through a cladogram: [IMAGE]

The reptiles first appeared in the early Carboniferous, having evolved

from labyrinthodont amphibians. They had several distinct advantages

over the amphibians that allowed them to flourish during the cold, dry

Permian period. These lead them to be the most successful group of

vertebrates and this period was referred to as the "age of reptiles."

They exploited all terrestrial niches, a few marine and even one group

took to the air. No other group of vertebrates had ever displayed such

diversity and mammals today are their only match. They were the first

group of tetrapods to successfully overcome the major problems of

terrestrial life, namely desiccation, thermoregulation and

respiration.

Adaptations to withstand desiccation

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Unlike amphibians reptiles are able to tolerate dryer conditions and

avoid desiccation. This allowed them to exploit more niches and

therefore achieve greater radiation. They did this in a number of

ways: 1 Skin. Reptilian skin is impermeable to water due to its unique

structure. It has a thick dermis and a thick epidermis. The relative

thickness of these layers helps somewhat in water conservation but it

is the components of the epidermis that make the skin waterproof. See

diagram: The α-keratin makes up the lower layer and is softer and more

pli...

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...whilst it is on land, something like a suspension bridge. Unlike the

chelonia, crocodiles do show a great deal of parental care, they build

and guard nests, help their young to hatch and acre for their young in

nursery pools for several weeks after hatching.Summary

As seen from this essay the diversity and subsequent biology of

reptiles is very wide and encompasses many niches. However reptiles

today are nowhere near as prolific as they were in the Mesozoic era

where they ruled the earth and exploited hundreds, if not thousands,

more niches. The real diversity and biology of reptiles was seen about

60 million years ago, before the mammals got a hold. But the only way

to investigate that is through the fossil record and that will never

give us all the information needed to draw a complete picture of

reptile diversity.

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