Tetrapods vs Amphibians
The difference between tetrapods and amphibians should be well understood in order to evade the confusion. Some amphibians are tetrapods; some reptiles also fall under the realm of tetrapods, but not all the reptiles or amphibians could be categorized as tetrapods. A proper understanding about tetrapods and amphibians separately would pave the way to identify these two types better than not. Since this article summarizes the characteristics of those two types of animals, the presented comparison on the difference between them would make it interesting for anyone.
Tetrapods are defined as the vertebrates with four limbs. Many reptiles, many amphibians, all the mammals, and all the birds fall under the group tetrapods. That means most of the vertebrates are tetrapods, but not all. Tetrapods started to evolve on the Earth before 400 million years from today. Many of the tetrapods resulted from the amphibians and the early tetrapods lived in water and have been feeding on fish, but secondarily they moved to lands as the fossil evidences reveal. According to the evolutionary biologists, there would have been two types of vertebrates diverged as fish and tetrapods. As the theories of evolution of tetrapods describe, the earliest tetrapods were Panderichthys, it was an aquatic animal, and Ichthyostega and Tikaalik could live in both water and land. From there on, the land living amphibians and the reptiles have been evolved up to mammals. However, tetrapods have two forelimbs that are mostly known as hands and two hind limbs or the legs. Except in primates, all the four limbs are used in walking. In addition, they developed lungs, padded or hoofed feet, ears and nostrils, fur or feathers and keratinized skins as adaptations for a terrestrial life. However, some animals decided to go back to water (whale, dolphin, penguin). Among the amphibians and reptiles without limbs, some still have rudimentary limbs and python is an example for that.
Amphibians evolved from fish before 400 million years from today. Presently, there are over 6,500 species living on the Earth, and they have been distributed through all the continents including the unique Australia. Amphibians can inhabit both aquatic and terrestrial ecosystems, but most of them go to water to mate and lay their eggs. Usually, the amphibian hatchlings start their lives in water and migrate to land, if it is a terrestrial species. That means, at least one stage of their life cycle is spent in the water. During their aquatic life as a larva or tadpole, amphibians take the appearance of small fishes. The tadpoles undergo the process of metamorphosis from larvae into adults. Amphibians have lungs for air breathing in addition to their skin, oral cavity, and/or gills. Amphibians are of three body forms; Anurans have a typical frog-like body (Frogs and Toads); Caudates have a tail (Salamanders and Newts), and Gymnophions have no limbs (Caecilians). Therefore, except for caecilians all other amphibians are tetrapods. They do not have scales on their skins, but it is a moistened body cover enabling gas exchange. Usually, amphibians are rarely found in a desert climate, but very common in damp and wet environments. In addition, they inhabit freshwaters than saltwater environments. Since they are extremely sensitive for environmental changes, amphibians are important as bio indicators. However, the environmental pollution usually affects amphibians more than other life forms.
What is the difference between Tetrapods and Amphibians?
• There are much more species of tetrapods than amphibians.
• Tetrapods have four limbs, but not all the amphibians do.
• The vast majority of tetrapods are terrestrial while amphibians are always towards aquatic or wet environments.
• Most of the tetrapods have scaly, furry, or feathery skins while amphibians have moistened skins.
• Usually, amphibians are smaller compared to tetrapods in their body sizes.