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Key Characteristics
1. Strong, bony skeleton, including toes and claws
2. Ectothermic metabolism
3. Dry, scaly, almost watertight skin
4. Amniotic eggs, almost watertight
5. Respiration through well-developed lungs
6. Heart ventricle partially separated by a septum
7. Internal fertilization of eggs
Temperature Regulation
Reptiles are ectotherms They regulate their body
temperature by behavior – basking in sunlight or seeking shade
At colder outside temperatures they become sluggish
This limits their geographical range
Water Retention
Watertight skin:Light, flexible, overlapping scales
Watertight eggs:Internal fertilizationTough, leathery shell Amniotic egg which contains
both water and food for the embryo
Respiration
No cutaneous respiration due to scaly skin
Lungs have many internal folds to increase surface area and therefore efficiency
Strong rib muscles aid in breathing The heart has a right and left atrium
and a partially divided ventricle which helps to separate high O2 blood from low O2 blood
Reproduction
Fertilization occurs within the female’s body
Most reptiles are oviparous – the young hatch from eggs laid outside the mother’s body; only a few species care for their young
Some reptiles are ovoviviparous – the eggs are kept inside the mother’s body until hatching; this reduces the risk from predators
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