12&13_predator avoidance '09

12&13_predator avoidance '09 - 1 Darwin’s theory...

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Unformatted text preview: 10/8/2009 1 Darwin’s theory focused on gradual change . How could intermediates be of benefit? len len cup cup array array pinhole pinhole Gradations now known to occur among living forms. lens lens Discussion of ‘flaws’ Discussion of ‘flaws’ arose in biology when ID advocates argued that eye s t p rf ct t h v Is vertebrate eye flawed? Is vertebrate eye flawed? was too perfect to have evolved via natural selection. Backwards retinal organization is a flaw unless a function can be defined. Spines and such: Spines and such: morphological traits suggest that predation exerts strong selection. Behavior also adapted for avoidance of predation. Three stages in the process of predation: Detection Detection Capture Capture Consumption Consumption (death) (death) A. Avoid Consumption A. Avoid Consumption Fighting back Fighting back is a time-honored defense. 10/8/2009 2 Behavior enhancing Behavior enhancing morphology morphology (Why not always be a ball of spines?) Chemical defenses Chemical defenses are everywhere! vinegaroon Bombardier beetle Bombardier beetle sprays attacker; Beetle can aim spray with precision; Spray is irritating benzoquinone benzoquinone in boiling water. hydrogen peroxide (H 2 O 2 ) and hydroquinone hydroquinone in ‘reservoir’ Catalases and peroxidases in ‘reaction chamber’ When attacked, reservoir empties into reaction chamber; Enzymes catalyze production of benzoquinone, O 2 , and HEAT . O 2 causes boiling solution to propel out of back end! Elegant ‘design.’ But presumed to have evolved via natural selection. There are a variety of species of spraying beetles that provide for a series of intermediate stages. nudibranchs nudibranchs ‘borrow’ defenses from jellyfish prey. incorporate stinging cells called cnidocytes cnidocytes called cnidocytes cnidocytes from jellyfish into their tissues. They are defended from predation by their prey… 10/8/2009 3 Nematocyst discharge Nematocyst discharge occurs in ca. 700 nanoseconds. Force generated is equivalent to a bullet. Pipevine swallowtail butterfly Some butterflies sequester noxious noxious chemicals chemicals from host plants while feeding as caterpillars. Birds learn to avoid these butterflies. Monarch butterfly Same Same strategy… must be independently strategy… must be independently evolved evolved B. Avoid Capture B. Avoid Capture Take flight....
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12&13_predator avoidance '09 - 1 Darwin’s theory...

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