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Species
Basic Characteristics of a Reptile
Reptiles are a diverse group with a wide array of extinct lineages
represented today by lizards, snakes, turtles, and crocodiles.
Reptiles have several adaptations for terrestrial living not generally
found in amphibians including the shelled egg and a waterproof
skin.
Scales
Scales containing the protein keratin waterproof the skin of a
reptile, helping to prevent dehydration in dry air. Keratinized
skin (skin that has been transformed into a tough fibrous outermost
layer) is the vertebrate equivalent of the chitinized cuticle
of insects and the waxy cuticle of land plants. Because it cannot
breathe through its dry skin, a reptile must obtain all of its
oxygen with its lungs.
Reproduction
Although viviparous reptiles exist (reptiles that give birth to
live young), most species lay eggs on land; parchmentlike shells
prevent them from drying out. The embryo develops in the fluid
of an amniotic sac within the egg. The evolution of the amniote
egg, a shelled egg with a self-contained "pond" of amniotic
fluid, enabled vertebrates to complete their life cycles on land
and sever their last ties with their aquatic origins. Fertilization
in reptiles must occur internally, before the shell is secreted
as the egg passes through the reproductive tract of the female.
Cold-blooded Animals
Reptiles are sometimes labeled "cold-blooded" animals
because they do not use their metabolism to control body
temperature. But reptiles do regulate body temperature by using
behavioural adaptations. Many lizards can maintain an internal
temperature of about 37°C by basking in the sun when the
air is cool and seeking shade when the air is too warm. Since
they absorb external heat rather than generating much of their
own, reptiles are said to be ectothermic, a term more appropriate
than "cold-blooded."
By heating directly with solar energy rather than with food, a
reptile can survive on less than 10% of the calories required
by a mammal of equal size. Having relatively modest food requirements
and being adapted to dry conditions, many reptiles thrive in the
deserts.
Reptiles in British Columbia
There are about 40 species of turtles, lizards, and snakes that
occur in Canada as a whole; 18 of these (6 turtles, 3 lizards,
9 snakes) have been recorded in British Columbia. Although the
number of species is small, British Columbia has a relatively
rich diversity of reptiles compared to other parts of Canada,
due to the different habitats in British Columbia.
Endangered Species
Several species of reptiles are endangered in interior regions
of the province for various reasons. The primary impact on their
distribution comes from a loss of suitable habitat. Their habitats
are being diminished for development and agricultural purposes.
Two endangered species of Reptiles inhabit the dry Thompson-Okanagan
region of southern British Columbia: the Night Snake (Hypsiglena
torquata) and the extirpated, Short-horned Lizard
(Phrynosoma douglassii). this section sponsored by: |
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