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Evolution explains the emergence of different species on earth and the respective functions of their structures. Lungs are among the organs highly studied by paleontologists to understand the divergence of organisms over time. Charles Darwin, the father of evolution believes that lungs evolved from gas bladders in lower vertebrates, precisely aquatic animals. The reason for Darwin’s claim is the commonalities between the lungs and gas bladders, such as swim bladders. Even though the gas bladders and lungs are used for different functions, they develop from the same body part, that is, the pharyngeal. The two organs also have a good supply of blood and are used to manipulate air. However, the purpose of evolution is to alter the functions of a body structure due the intensification of the purposes of the original structures. The existing structure tends to change to match the new functions. For lower vertebrates, gas bladders help in gaining buoyancy, however, once the vertebrates colonized the terrestrial ecology, the function of the gas bladder intensified to include a gaseous exchange.
The gas bladder in lower vertebrates underwent modification, which transformed its structures as well as functions while eliminating the previous organ altogether. As the size gradually grew, the lungs developed mechanical support in a form of a continuous framework of elastic collagen fibers to match the functional needs. In the lower vertebrates with low metabolic demands, the lungs are ventilated with buccal gas pumps that supply air through the movement of identical muscles. On the contrary, higher vertebrates have high metabolic needs that require more oxygen. Hence, the lungs have been divided into progressively smaller air spaces and long narrow airways, which rendered the gas pump obsolete. Another essential modification of the lungs in terrestrial vertebrates is the development of the diaphragm. The new feature is an advanced and more efficient form of gas pump whose relaxation and contraction movements provide sufficient energy for exhalation and inhalation. Thus, evolution leads to change in form and function to match the new demands of the organisms.
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