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Evolution of Echolocation in Dolphins

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Evolution of Echolocation in Dolphins 3/13/13 Evolution of Echolocation in Dolphins http://onthegoinmco.com/wp-content/uploads/2012/12/Discovery-Cove-Baby-Dolphin.jpg.jpg Outline * Echolocation * What is it? * What it is good for? https://i.chzbgr.com/maxW500/6583346176/h4CCE80A7/ * Overview on Echolocation in Dolphins * Brain Size Analysis * Important Proteins and components * Prestin and Others * A brief summary of bats * Comparative Evolution of Echolocation http://govashon.files.wordpress.com/2008/10/orca2.jpg * Dolphins vs. Bats * Phylogenetic Tree Analysis http://www.globalanimal.org/wp-content/uploads/2010/11/BABY- DOLPHIN-LEARNS-TO-SWIM.jpeg 1 3/13/13 What is Echolocation? * Is the emission of sound waves into the environment, and then listening to the returning sounds that are bounced off objects. * Toothed whales (Including dolphins), and two species of bat are capable of echolocation. http://en.wikipedia.org/wiki/Animal_echolocation What is Echolocation? 2 3/13/13 3 3/13/13 More on Dolphin Echolocation * Eco-locating dolphins can detect targets at ranges of 100 + meters. * Signals * Pulses * Example: The bottlenose dolphin can hear over a wide frequency range between 75Hz to 150kHz. They produce directional broadband clicks in sequence. http://www.dosits.org/science/soundsinthesea/peopleanimalsuse/echolocation/ What is it good for? * Communication * Navigation of environment * Locate and hunt Prey https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcSojb- biH9F_Rrz7FjSQhn8XqueAwGA4wG0Fq4xvPn0MNGZDKQC2w * The swimming bladder of fish * Studies show discrimination between different type of fish possible http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0014054.g002&representation=PNG_M 4 3/13/13 Brain Size * Study of brain size in toothed whales * Encephalization * The amount of brain mass compared to the body of the organism * Only humans have larger brains to body mass then modern dolphins The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology Volume 281A, Issue 2, pages 1247-1255, 20 OCT 2004 DOI: 10.1002/ar.a.20128 Echolocation with Dolphins * Important gene that was found in dolphins: - Prestin - Where is Prestin located? - Prestin is found in outer hair cells that serve as an amplifier in the inner ear, refining the sensitivity and frequency selectivity of the mechanical vibrations of the cochlea. * Natural Selection caused for this Prestin 5 3/13/13 …and now a bit about bats. Bats echolocation * Bats typically emit much longer signals and a wider variety of different types of signals than dolphins. * Signals used by some bats are suited to detecting Doppler shift are affected by the velocity of both bat and prey so that echoes can carry Doppler information * Echolocation signals used by bats are brief sounds varying in duration from 0.3 to 300 ms and in frequency from 12 to 200 kHz 6 3/13/13 Some other facts about echolocation * Each click last about 50 to 120 microseconds for dolphins. * The speed of sound in water is 1.5 km/sec (0.9 mi/sec) which is five times faster than in air. This difference should have a large impact on how echolocation is used by both species. * High frequency sounds don’t travel far in water * Echolocation is most effective at close to intermediate range, about 5 to 200m (16-656 ft) for targets 5 to 15 cm (2-6 in) in length. 7 3/13/13 Convergent Evolution * Other genes studied as well * Hair bundle motility * Outer hair cells in the cochlea * Proteins encoded by genes Cdh23, Pcdh15 * Neurons and nerve fibers in the brain * Ca2+ censor * Otof Convergent Evolution * Using Tree Analysis to show convergent/parallel evolution * Trees built on nucleotide and amino acid sequences * Amino acid sequences incorrectly grouped all echolocators together * Statistically different from random expectations P <0.001 8 3/13/13 Review * Mutation and natural selection has caused dolphins to have developed large brains and the ability of echolocation. * Dolphins and Bats are an extreme example of convergent evolution * Similar pressures * Same genes appear * Using phylogenectic trees 9 3/13/13 Sources * "Animal Echolocation." Wikipedia. Wikimedia Foundation, 26 Feb. 2013. Web. 28 Feb. 2013. <http:// en.wikipedia.org/wiki/Animal_echolocation>. * "Bioacoustics: The International Journal of Animal Sound and Its Recording." Talor & Francis, 1997. Web. * Davies, K., J. Cotton, J. Kirwan, C. Teeling, and S. Rossiter. "Parallel Signatures of Sequence Evolution among Hearing Genes in Echolocating Mammals: An Emerging Model of Genetic Convergence." Heredity, 14 Dec. 2011. Web. * Freeman, Scott. "Evolutionary Analysis, 4th Edition." Freeman/Herron, Evolutionary Analysis, 4th Edition. N.p., 11 July 2009. Web. * Marino, Lori, Daniel McShea, and Mark Uhen. "Origin and Evolution of Large Brains in Toothed Whales." N.p., 20 Oct. 2004. Web. 24 Feb. 2013. * Shen, Yong-Yi, Gui-Sheng Li, Robert Murphy, and Ya-Ping Zhang. "Parallel Evolution of Auditory Genes for Echolocation in Bats and Toothed Whales." PLOS Genetics:. PLoS Genet., 8 June 2012. Web. 24 Feb. 2013. * "Toothed Whales." Wikipedia. Wikimedia Foundation, 22 Feb. 2013. Web. 01 Mar. 2013. <http:// en.wikipedia.org/wiki/Toothed_whales>. * Yovel, Yossi, and Withlow Au. "How Can Dolphins Recognize Fish According to Their Echoes? A Statistical Analysis of Fish Echoes." Unbound MEDLINE : How Can Dolphins Recognize Fish According to Their Echoes? A Statistical Analysis of Fish Echoe. N.p., 19 Nov. 2010. Web. 26 Feb. 2013. Any Questions? http://24.media.tumblr.com/tumblr_m4nf6lIdUZ1qe3p5fo1_1280.jpg 10 3/13/13 Questions * 1. When doing tree analysis, one group of scientists found that amino acid sequences of a gene grouped all echolocating bats and dolphins together. Why would this be considered incorrect as a phylogenectic tree? What is this tree better explaining, i.e. what is the type of evolution going on? * 2. What evidence suggests dolphins and bats have undergone convergent evolution? In what ways are they similar? * 3. Dolphins have developed a very sensitive system to track prey. Explain the red queen hypothesis, and how it might explain why this system might have been positively selected for? 11 .
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