Reptiles
As opposed to mammals and birds, reptiles have neither fur nor feathers, but scales. Reptiles can not be confused with amphibians because reptiles have dry, water-proof skin and eggs, as well as internal fertilization and more advanced circulatory, respiratory, excretory, and nervous systems.
- Reproduction: the parent will lay the egg and with in a certain time period the offspring will come out the egg unlike mammals that give birth to their young alive.
- Amniotic Egg: this adaptation is important because this egg type has allowed them the offspring survive with out it having to dry out. In order for this to happen there has to be an egg shell to keep all water/liquid in and let oxygen come in, a small food supply for the offspring to consume while in the egg (yolk), an allantois to collect all waste secreted from the offspring, and the amnion to encase the developing animal in a liquid sac.
- Reptiles are ectothermic which means they obtain heat from outside sources.
- Circulatory: Modern reptiles do not have the capacity for the rapid sustained activity found in birds and mammals. It is generally accepted that this lower capacity is related to differences in the circulatory and respiratory systems. All groups of modern reptiles have a completely divided atrium. In the four major living groups of reptiles, the ventricle is at least partially divided. When the two atria of a lizard’s heart contract, the two streams of blood (aerated blood from the lungs in the left atrium and nonaerated blood from the body in the right atrium) flow into the left chamber of the ventricle. As pressure builds up in that chamber, the nonaerated blood is forced through the gap in the partition into the right chamber of the ventricle. Then, when the ventricle contracts, nonaerated blood is pumped into the pulmonary artery and then to the lungs, whereas aerated blood is pumped into the systemic arteries (the aortas) and so to the body.
- Scales: form by a folding of the epidermis during embryonic development. The result is skin with a scaley extension. Thus scales are a form of integument. Skin can be seen between the scales in certain species, while it is readily visible in snakes that are swallowing something large. The scales serve as the skin for reptilians to protect their organs.