Bats and toothed whales are model organisms for the investigation of sensory processing. These two animal groups evolved echolocation, an active sense relying on the integration of auditory, vocal and motor systems. In order to forage in darkness, these animals emit intense high frequency sounds and use information from the corresponding echoes to locate, discriminate and track prey, often at great distances, (Kloepper et al., 2014,). Sound propagating through open space is attenuated by 6 dB for each doubling of distance to the object, and echoes returning from a small object are attenuated by a further 6 dB for each doubling of distance. Processing such a large range of echo intensities poses a challenge for the animal's auditory system. To compensate, echolocators maintain a constant perceived echo level by changing both the transmit and receive sonar systems, (Kloepper et al., 2014,).
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An example of this is the streamlined, bullet-type shape of sharks and dolphins that allows them to swim fast through the water. However, sharks are fish and dolphins are mammals and they are very far apart on the evolutionary tree. Because organisms that do not have a common ancestor can evolve in the same ways is powerful evidence for natural selection, (Editors, 2017).
Biologists have long debated how different animal species independently developed echolocation, the sonar-like mechanism in which animals listen to their own clicks and calls echoing back from obstacles or prey. In the study released, biologists led by Stephen Rossiter and Joe Parker at Queen Mary University of London, drew upon the largest dataset ever to look for convergent evolution in 2,326 genes shared by 22 mammals, including six bats and the bottlenose dolphin, ?("Convergent evolution seen in hundreds of genes," n.d.).
Divergent