Lizards are a large group of reptiles. There are thousands of lizards on Earth, which can be divided into lizard species such as geckos, iguanas, and monitor lizards. Each lizard species can also be divided into subspecies. There are often hundreds of different subspecies of lizards within a species.
Geckos include hundreds of different types of lizards and many more are believed to be unknown. These lizards vary in size. The smallest known gecko, the Jaragua Sphaero, generally only grows up to .7 inches (18 mm). The tokay gecko is the largest animal in this lizard species and it can grow up to 15 inches (40 cm). Geckos are carnivores whose diets include items such as insects, eggs, and tiny mammals.
Most geckos are nocturnal reptiles. The majority of their hunting is done at night. It is believed that these animals have special visual abilities that allow them to differentiate between colors in very dim settings. These lizards are usually the prey of snakes. The most unique characteristic of this lizard species is that it is the only one that has lizards that can make noise.
Iguanas are large lizards that can be found in deserts or in the tropics. There are eight groups of lizards within this particular species. This lizard species includes the marine iguana, which is the only lizard that swims in the sea and eats seaweed and algae. All iguanas are herbivores, however, and they generally eat plants and fruit. Excellent eyesight allows these animals to identify food sources and predators at long distances.
Female iguanas lay dozens of eggs in buried nests. When the young hatch, they must dig their way to the surface. Thereafter, they have a possibility of living up to about 30 years.
Monitor lizards are a species with great size variations. This group of reptiles includes the largest known living lizards, which are Komodo dragons. These lizards can grow up to 364 pounds (165 kg) and 10 feet (3 m) long. Komodo Dragons are aggressive and are considered a threat to humans, unlike most lizards. All monitor lizards are carnivores, however, and they generally sustain themselves with a diet that includes snakes, squirrels, and other lizards.
Monitor lizards' aggression is not limited to other species. Males commonly fight each other during mating season. The females lay batches of eggs that can vary seven to a few dozen. The babies use an egg tooth to liberate themselves from their shells.