Iguanas are reptiles and nearly all reptiles lay eggs. There are some reptiles that do not lay eggs, but they are very rare. Female iguanas usually lay a clutch of eggs every year once they're mature. If there is no male iguana, she will still lay eggs, but they won't be fertile. If iguanas mate, several weeks after mating, the female green iguana digs a nest and lays about 20 to 60 eggs. The eggs are left in the nest and hatch about 3 to 4 months later.

For more on iguana reproduction, check out this website:

For more on the iguana in general, see this Wikipedia article:

For more on reptiles, see this Wikipedia article:

In biology, it's often useful to separate different organisms depending on broad characteristics.Iguanas are grouped into the class Reptilia, and with a few exceptions, every organism in that group lays shelled eggs when they reproduce. Separating organisms that way can help you find similarities that wouldn't seem obvious. For example, because reptiles and birds both lay shelled eggs, scientists started looking at other things that they have in common and realized that it's likely that reptiles and birds both evolved from a common ancestor!