Reptiles
Reptiles were estimated to have arrived around 320 million years ago during the Carboniferous perod. During that period there were not any true reptiles, but species of reptilian-like amphibians. Reptiles are tetrapod vertebrates and descended from their past four-limbed ancestors. The tetrapods were the first four-limbed species with digits when the lobe-fins of aquatic species evolved allowing movement on land while retaining their aquatic features. Unlike amphibians, reptiles do not endure an aquatic larval stage. Most reptiles are oviporous egg-laying species. The extraembryonic membranes within the egg shells laid by reptiles assist in keeping in moisture so that the eggs do not dry out on land, helping sustain the reproductive process unitl the new-borns hatch.
However, like amphibians, they are ectothermic and rely on the environment to maintain their body temperature. Most reptiles thermo-regulate, sun bathe, to absorb heat. We have all seen crocodiles sitting in the sun just relaxing. Large reptiles have a level of homothermy where their body temperature does not fluctuate too much in response from their environment. This process is known as gigantothermy where the large reptiles can keep a stable body temperature with little need from the environment to maintain their homeostasis. Reptiles solely use lungs to breathe, unlike amphibians which can use their skin as well as small lungs for oxygen absorbtion. Reptiles tend to have impermeable skin and are able to use their rib cage to help venitilate the lungs for breathing.
Reptiles reproduce sexually, although some species have been known to reproduce asexually, while reptiles use the same opening from the cloaca to excrete waste and hide their genetilia.
Male snakes as an example, tuck their genitila inside their cloaca and when mating their genitals protrude out the anus and intertwine with the female who will accept the male deposit in her cloaca. Snakes are considered to be legless lepidosaurs which essentially evolved from lizards.
Reptiles digestive system follows the path from their mouth through their esophagus, which in snakes can be almost half the length of their body. That is a long throat!. The food is then deposited into the stomach for enzyme breakdown with the food then passed into the small intestine for nutrient absorption followed into the large intestine then excreted out through the anus or cloaca opening.
We dissected a snake in our laboratory time and followed the digestive path.
However, like amphibians, they are ectothermic and rely on the environment to maintain their body temperature. Most reptiles thermo-regulate, sun bathe, to absorb heat. We have all seen crocodiles sitting in the sun just relaxing. Large reptiles have a level of homothermy where their body temperature does not fluctuate too much in response from their environment. This process is known as gigantothermy where the large reptiles can keep a stable body temperature with little need from the environment to maintain their homeostasis. Reptiles solely use lungs to breathe, unlike amphibians which can use their skin as well as small lungs for oxygen absorbtion. Reptiles tend to have impermeable skin and are able to use their rib cage to help venitilate the lungs for breathing.
Reptiles reproduce sexually, although some species have been known to reproduce asexually, while reptiles use the same opening from the cloaca to excrete waste and hide their genetilia.
Male snakes as an example, tuck their genitila inside their cloaca and when mating their genitals protrude out the anus and intertwine with the female who will accept the male deposit in her cloaca. Snakes are considered to be legless lepidosaurs which essentially evolved from lizards.
Reptiles digestive system follows the path from their mouth through their esophagus, which in snakes can be almost half the length of their body. That is a long throat!. The food is then deposited into the stomach for enzyme breakdown with the food then passed into the small intestine for nutrient absorption followed into the large intestine then excreted out through the anus or cloaca opening.
We dissected a snake in our laboratory time and followed the digestive path.
Photographs were taken by Gary Adams within Lab Disection classes at the Bermuda College.
Reference
Vertebrate Zoology, "Snake Dissection", retrieved from website April 13, 2013, http://www.savalli.us/BIO370/Anatomy/5.SnakeDissectionLabel.html