Reptiles are able to survive in a wide range of climates thanks to a suite of physiological and behavioral adaptations. From regenerating tails to avoiding predators, there is much to admire about these cold-blooded creatures.
크레스티드게코All reptiles lay eggs enclosed in shells and are ectothermic, meaning that they use their environment to control body temperature. Some, such as snakes, are ovoviviparous and lay eggs that hatch internally. Others are viviparous and give birth to live young.
Adaptations for Life on Land
Reptiles are ectothermic vertebrates that evolved into land-living forms, such as snakes, lizards, turtles, and crocodilians. Their major adaptation for living on land is the development of lungs to replace gills, which allows them to venture away from aquatic environments without having to surface to breathe. They also lay eggs with a thick, leathery coating or hard calcium shells that can survive on dry land. Some reptiles, such as snakes, even carry their eggs inside themselves until they hatch (ovovivipary).
Reptilian scales are another important adaptation to life on land. These tough, overlapping structures protect against injury and loss of water.
In addition to lungs and scales, reptiles have many other features that make them well suited to life on land. For example, their thick, scaly skin helps conserve moisture in humid habitats, their kidneys produce highly concentrated urine to reduce water loss from excretion, and they have efficient excretory systems. They can also regulate their body temperature by shuttling in and out of shade, adjusting contact with the ground to control heat transfer (conduction), changing color to absorb more or less sunlight (solar thermoregulation), or using warm rocks to bask in.
In terms of behavior, most reptiles avoid confrontation with predators by hiding underground or underwater, camouflaging, or displaying threat displays. They may also use behavioral strategies to find food, including stalking or waiting in ambush. Most reptiles are carnivorous, catching live prey or scavenging on dead animals. Some, such as the African chameleon, have sticky tongues that they use to lure insects into their mouths. A few species, such as terrestrial turtles and some lizards, are herbivorous, eating only plants.
Adaptations for Breathing
Reptiles don’t rely on their skin for oxygen like amphibians do, but rather they use lungs. Lungs are spongy, sac-like organs in the thoracic cavity that inhale and exhale air to help with gas exchange. The respiratory system also includes a larynx and trachea, which are located in the throat.
When snakes crush their prey, they put a lot of pressure on the victim’s chest — but this pressure can suffocate the snake, too. To avoid suffocation, snakes can activate a set of muscles around their long rib cage to inflate the lungs as needed. Scientists have been able to see how this works on x-rays and electrical recordings of the snakes’ nervous systems.
Most reptiles, including those that live close to water (like crocodiles) have two lungs. However, some lizards and snakes have only one lung. This allows them to breathe while on land, which is important because it enables them to travel far from their aquatic habitats.
The scaly skin of most reptiles is waterproof, not to keep the animal from getting wet but rather to conserve moisture inside their bodies. This helps them survive dry environments such as deserts. Reptiles also tend to have efficient excretory systems that remove as much water as possible from waste to minimize the amount of water lost during defecation.
Adaptations for Movement
Reptiles use muscles to move and gain access to food and shelter. Their skin contains a substance, called keratin, that helps keep them hydrated. Their lungs allow them to take in air for respiration. Like other mammals, reptiles can also breathe through their skin, but this is not a good idea because it reduces the surface area available for oxygen exchange. In lizards, snakes, and crocodiles, the muscle of the chest wall that surrounds the lungs can be used to help push air into the lungs while the animal is moving.
Reptilian movement is usually slow and methodical. This is a defense against predators, as well as an adaptation for avoiding extreme temperatures. Many reptiles can quickly crawl into undergrowth or find a shady spot to hide. Some, like sea turtles and crocodiles, can sink down into the water to escape danger.
A key step in reptiles’ transition to land was the development of lungs in place of gills. Gills are useful in water, but they would not survive on dry ground. Reptiles also developed a way to lay eggs that can survive on land. Many types of reptiles now lay hard-shelled eggs that use internal fertilization to create viable babies.
As a result, the bones of many reptiles’ limbs have shortened and elongated to look more snake-like. This body shape is thought to improve locomotion in fossorial (burrowing) habitats or for navigating cluttered environments by reducing the drag on the reptile’s body as it moves through space.
Adaptations for Food
Reptiles fill many different ecological niches in their natural habitats. They are found from tropical forests to arid deserts and even ocean depths. Some are herbivores and munch on grasses, fruits and vegetables. Others are carnivores or scavengers and eat a wide variety of meat, insects and other invertebrates.
The skin of reptiles is covered in scales, bony plates or a combination of both. These occlusive skin structures help reduce water loss.
In addition, like all vertebrates, reptiles are cold-blooded and depend on their environment to regulate body temperature. Unlike mammals that produce their own internal heat, reptiles are considered ectothermic and use their bodies to absorb the heat from the sun or earth. They have to seek out sunny places to warm up and shady spots or caves to cool down.
Moreover, the scaly skin helps reptiles avoid overheating, which would require them to expend a lot of energy for respiration. Unlike amphibians that can breathe through their skin, reptiles use their lungs for breathing.
When threatened, many reptiles display their bright colors in a threat show to scare away their predators. They may also flatten the head and cranial area, especially in the case of monitors and Asian rat snakes, to increase their size. The display also exposes their bright scales to the predator for better visibility.