These goats may have pharmaceutical compounds in their milk.
There is a shortage of hearts for heart transplant operations.
There are seven features that define the reptiles.
Birds are related to flight.
More than 17,000 species of birds are part of the Reptilia group, which is a very successful group of animals.
The following characteristics show that reptile are adapted to life on land.
The following are the characteristics of all reptiles.
With the exception of snakes, lizards have two pairs of limbs with five toes each.
A reptile can be used for climbing, running, paddling, or flying.
The skin is impermeable to water.
The skin in reptiles is very thin.
There are many lizards and snakes that change colors.
The lungs are more developed than the salamanders.
The rib cage is helpful in breathing.
The heart does not allow mixing of blood.
The ventricle is divided either partially or completely by the septum.
The mixing of oxygen-poor blood and oxygen-rich blood is reduced if it is partially divided.
Oxygen-poor blood is separated from oxygen-rich blood if the septum is complete.
The kidneys are in good shape.
Less water is required to rid the body of nitrogenous waste because the kidneys excrete uric acid.
The ability to survive on a fraction of the food required by birds and mammals is a trait of most reptiles.
The warm body temperature is maintained by warming themselves in the sun.
Sexes are separate and fertilization is internal.
Nitrogenous waste is removed and the embryo is provided with oxygen, food, and water.
The amnion is a sac that fills with fluid and provides a private pond for the embryo.
At some point in the Carboniferous period, an ancestral amphibian gave rise to the amniotes.
The amniotes include mammals and birds.
The amniote embryo has an amnion.
The mammals, in which the skull is and has one opening behind the orbit, are on Page 553.
The diagram shows an overview of the presumed evolutionary relationships among amniotes.
The amniote is the descendant of the amniote.
This figure shows a historical understanding of turtle evolution.
The turtles are archosaurs along with crocodiles and birds according to a modern view.
The eggshell is flexible and leathery.
The embryo is inside the egg.
The chorion aids in gas exchange, the allantois stores waste, and the amnion protects the fluid from drying out.
The embryo gets its nutrition from the yolk sac.
Systematists are looking at the evolutionary relationships of the lizards and birds.
The turtles, or anapsids, are separate from the rest of the reptiles, which are diapsids, in the classical view of reptile evolution.
The anapsids are just highly specialized diapsids.
The classical view of reptile evolution is presented here because the evidence in support of this modern view is still being debated.
The pterosaurs of the Jurassic period had a keel for the attachment of large flight muscles and air spaces in their bones to reduce weight, and the thecodonts were diapsids that gave rise to the ichthyosaurs, which returned to the aquatic environment.
The bones of the fourth finger supported their wings.
The thecodonts gave rise to crocodiles and dinosaurs.
Between the dinosaurs and the birds there was a sequence of transitional forms.
Skull openings in front of the eyes and clawed feet are derived from the crocodilians and birds.
The designation archosaurs is used for the crocodilians, dinosaurs, and birds.
The animals are more related to each other than they are to snakes and lizards.