Reptiles like crocodilians, snakes, lizards, and tuatara mainly excrete uric acid as waste, while turtles excrete urea like mammals. Their kidneys filter large quantities of blood. Aquatic reptiles tend to excrete ammonia, while terrestrial reptiles convert nitrogenous waste to insoluble uric acid to conserve water. Reptiles are poikilothermic and rely on environmental heat to regulate their body temperature within a functional range, emerging from burrows or altering skin coloration to thermoregulate as temperatures change.

1. Excretion is performed mainly by two small kidneys. In crocodilians,
snakes, lizards, and tuatara, uric acid is the main nitrogen-containing waste
product. Turtles, like mammals, mainly excrete urea. Their kidneys have
many nephrons. The functional kidneys of adult reptiles are called met
nephric kidneys. Kidneys filters large quantities of blood
EXCRETION IN REPTILES

2. MECHANISM OF EXCRETION
Most reptiles excrete uric acid. The urinary bladder or the cloacal walls
absorb water .nontoxic uric acid can be stored in egg membrane. In
terrestrial environment tend to possible the development of embryos.

3. EXCREATORY PRODUCT.
Aquatic reptiles tend to excrete a large proportion of these wastes as
ammonia in aqueous solution. Terrestrial reptiles, such as most snakes
and lizards, must conserve body water, and they convert their
nitrogenous wastes to insoluble, harmless uric acid, which forms a more or
less solid mass in the cloaca.

4. THERMOREGULATION IN REPTILES
DEFINITION •
Thermoregulation is the maintenance of body temperature within a range that
enable cells to function efficiently,

5. Poikilotherms (Cold-blooded):- Those animals in which body temperature is
varied with the environmental conditions are called Poikilotherms. 1.
Aquatic Poikilotherms:- Thermoregulation in aquatic Poikilotherms is a
simple phenomenon. Heat exchange in aquatic animals are largely by
conduction and convection. Thermal environment of aquatic animals is
relatively stable, Still seasonal variations do occurs in the surface layers of
the sea and the lakes.

6. Terrestrial Poikilotherms:-Terrestrial Poikilotherms maintain their body
temperature almost equal to that of the environment. However terrestrial
animals face greater temperature fluctuations. The heat balance of such
animals is more related to their water balance as compared to the aquatic
animals. In order to raise the body temperature the evaporation and heat
loss by conduction are to be reduced and the heat gain by radiation and
metabolic heat production are to be increased.

7. Lizards and other reptiles burrow at night when the desert or mountain
temperatures are at their lowest. Some heat from the day remains
underground and the reptiles body is prevented from freezing. At sun rise
the lizard, which may have reached a body temperature as low as 5 degree
during the night slowly emerges from its burrow to orient itself to the
sunlight so that the maximum heat is obtained. By proper orientation
lizards can attain body temperatures that are as much as 30 degree above
that of the air. Reptiles are poikilothermic and rely on their environment as
a source of heat to raise their body temperature

8. . In species of reptiles that have the ability to alter skin colouration such as
chameleons, geckos they can produce darker colours to increase the
absorption of early morning sun. This behavior allows them to reach
optimal temperatures faster and also reduces the amount of time spent in
the open which leaves them vulnerable to predation. Optimal temperatures
allow the reptile to function and metabolize however lower temperatures
can slow processes down. Typically the metabolic rate is 10% of the
equivalent size endotherm, this is an example of the low cost energy
needed to sustain an ectotherm

9. THE END