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| Description: Reptiles, known as egg-layers, form their eggs and it completes its embryological development outside the body of mother. However, some species are not following this pattern. A lizard species, yellow-bellied three-toed skink, forms the egg and keeps it inside of the body until baby lizard almost completes its embryological development. The level of this development inside the body changes depending on altitute and temperature. As altitude gets higher and temperature gets lower, these lizards almost gives birth to live babies. This change in birth style creates some problems and solution to these problems. The main problem is about nourishment of the embryo. The egg shell gets thinner to make breathing of embryo possible, then, the amount of calcium stored in the egg shell lowers. Since thin shell stores less calcium, baby lizards may have some health problems. James Stewart, a biologist, explains how lizards are evolving to solve this problem :"Now we can see that the uterus secretes calcium that becomes incorporated into the embryo—it's basically the early stages of the evolution of a placenta in reptiles" Picture Stats: Views: 1740 Filesize: 35.78kB Height: 450 Width: 594 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=9304 |