According to Charles Darwin, organisms have a natural tendency to inherit favorable traits of past generations into future generations as well as discard traits that are not so useful or have become obsolete in their usefulness (Gould, 2002). This is what is now knows as the theory of natural selection. The salamander is an amphibious creature with 500 species. They are generally characterized as having slender bodies with long tails and short legs. Most species of salamanders have four legs (Farrand, 2003).
The exception to this is the aquatic salamander belonging to suborder Sirenidae which only has two very small forelimbs and lack any hind limbs (Farrand, 2003). These creatures are often referred to as sirens (Farrand, 2003). In order to be able to explain the evolution of these aquatic salamanders through the use of Darwin’s theory of natural selection, it is important to take into consideration any possible uniqueness in the habitat, food source, and general way of life of this aquatic salamander that is not present in the cases of its relatives.
For example, the aquatic salamander’s diet includes small fish and shrimps (Farrand, 2003). These prey would not be so easily caught by creatures that have more terrestrial characteristics such as better developed fore and hind legs. It can be hypothesized that in the evolution of aquatic salamanders, more abundant food source in their natural habitat were free-swimming aquatic creatures.
Thus over their evolutionary years, the predecessors of the siren discarded their hind legs in favor of faster and better mobility in the water given its more buoyant physical structure with the absence of its legs. Natural selection made this happen so that the aquatic salamander can have better access to the more abundant food source available to them.
Farrand, M. (2003). Classifications of Animal Life in North American Internal Waters. N. Y. : McGruder & Sons Gould, S. (2002). The Structure of Evolutionary Theory. Harvard University Press.
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