circuits for escape III - Co-evolutionCo-evolution occurs...

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Unformatted text preview: Co-evolutionCo-evolution occurs when two (or more) species (or lineages) interact and their evolutionary trajectories depend on each other.Positive (e.g.--symbiosis): Plants and pollinators. Negative: plants and herbivores.Co-evolution may lead to an arms race.Evolutionary arms racehttp://www.yoursoldiersblog.com/media/IranMissles1.JPGhttp://www.tcappsbct.com/img/Patriot_missile_launch.jpgICBM misslesPatriot anti-misslesBats are major predators of night-active insectsBats emit ultrasonic calls which bounce off of flying insects, and they detect the echoes from the insects.http://www.saguaro-juniper.com/i_and_i/mammals/bats/pallid_bat.jpghttp://newsimg.bbc.co.uk/media/images/39604000/jpg/_39604945_horseshoebat203.jpgThere are even fish-eating bats and frog-eating bats!!!http://www.dkimages.com/discover/previews/970/90065064.JPGBats not only have large ears, many have oddly shaped noses because they call through their noses and this helps direct the sound.http://www.marquisandlord.com/images/barbastelle.jpghttp://www.dkimages.com/discover/previews/875/30039377.JPGUltrasonic cries of bats: typically 20-120 kHz.Surlykke & Kalko, 2008Calls of 11 species of bats. The top traces show how the amplitude of the call varies with time. The bottom traces show the frequency spectrum of the calls. They can exceed 100 kHz.Why do bats use ultrasonic calls?Why do bats use ultrasonic calls?Frequency Wavelength (inches)10 kHz = 1.3 inches20 kHz =0.67 inch50 kHz = 0.27 inch100 kHz = 0.13 inchIf the wavelength of a sound is greater than ~ 2x the object, the sound wave goes around the object and little energy is reflected. The wavelength must be smallerthan the size of the object to relfect sound energy back (I.e.-to make an echo).A typical moth is ~1 inchWhy do bats use ultrasonic calls?But, sound also attenuates in air proportionally to its frequency. High frequencies attenuate more. So a bat must call very loudly. Often > 120 dB. No soundUltrasonic pulseUltrasonic pulseSpeaker broadcasting artificial ultrasonic pulseRoederMoths detect the echolocation cries of hunting bats and avoid them.Hunter and hunted. In the top photo, a moth (bright streak) takes successful evasive action upon detecting the approach of a bat (broad streak across the photo). (The diffuse image is a tree in the background.) In the bottom photo, the two streaks intersect, indicating that this time the moth was unable to escape capture by the bat. intersect, indicating that this time the moth was unable to escape capture by the bat....
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This note was uploaded on 03/28/2012 for the course BIO 49593 taught by Professor Wanser during the Spring '10 term at University of Texas at Austin.

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circuits for escape III - Co-evolutionCo-evolution occurs...

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