Amphibians are a diverse group of animals that include frogs, salamanders and caecilians. They are characterized by their ability to live both in water and on land, their moist skin that helps them breathe, and their complex life cycle that involves metamorphosis from a larval to an adult stage. But which group of animals is most closely related to amphibians? The answer may surprise you.
Contents
Lobe-Finned Fishes: The Closest Living Relatives of Amphibians
According to the current scientific consensus, the group most closely related to amphibians is the living lobe-finned fishes. These are a small group of fish that have fleshy fins with bones and muscles, unlike the ray-finned fishes that have thin fins supported by bony rays. The living lobe-finned fishes include the coelacanths, which were thought to be extinct until 1938, and the lungfishes, which have lungs as well as gills and can survive in dry conditions.
The reason why lobe-finned fishes are considered the closest living relatives of amphibians is because they share a common ancestor with them. This ancestor was a fish-like creature that lived in the Devonian period, about 400 million years ago, and had features that were helpful in adapting to dry land. These features included lungs, bony limbs, a neck, and a skull with a movable jaw. Some of these creatures evolved into the first tetrapods, or four-limbed vertebrates, which gave rise to amphibians and other land animals.
Other Tetrapods: Equally Related to Amphibians
While lobe-finned fishes are the closest living relatives of amphibians, they are not the only ones that share a common ancestry with them. All tetrapods, including reptiles, birds and mammals, are equally related to amphibians because they share a common ancestor with them. This ancestor was a tetrapod that lived in the Carboniferous period, about 350 million years ago, and had features that were common to all land vertebrates. These features included a backbone, a rib cage, a four-chambered heart, and an amniotic egg.
The reason why reptiles, birds and mammals are equally related to amphibians is because they diverged from them at the same time. This divergence occurred when some tetrapods developed adaptations for living in drier environments, such as scales, feathers, fur, claws and teeth. These adaptations enabled them to cope with temperature fluctuations, water loss and predators. Some of these tetrapods evolved into reptiles, which gave rise to dinosaurs and birds, while others evolved into mammals.
Conclusion: Amphibians Are Related To Many Groups of Animals
Overall, there is ample evidence to suggest that amphibians are most closely related to other tetrapod vertebrates like reptiles, birds and mammals. The similarities in morphology, physiology and behavior make it clear that they have evolved from a common ancestor and likely still share many genetic traits with each other today.
However, the closest living relatives of amphibians are not other tetrapods but lobe-finned fishes. These are a small group of fish that have fleshy fins with bones and muscles that resemble limbs. They also have lungs that allow them to breathe air when water is scarce. These features indicate that they share a more recent common ancestor with amphibians than other tetrapods do.
Therefore, the answer to the question “which group is most closely related to amphibians?” is not straightforward but depends on whether we consider living or extinct groups of animals. If we consider living groups only, then lobe-finned fishes are the most closely related to amphibians. If we consider extinct groups as well, then all tetrapods are equally related to amphibians.
