Lecture 2 - Lecture 2 Staying Alive: Animal Defences...

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Lecture 2 – Staying Alive: Animal Defences [Concluded] Invisibility by Environment – an object may be classified as “invisible ” ( camouflaged ) if it cannot be noticed by use of sight due to environmental factors other than the fact that it doesn't reflect light. An object that might normally be seeable may be classified as invisible if it is: - Behind an object - The same color or pattern as the background (camouflage) - In an environment which is too dark or too bright - In a particular observer's blind spot Animal coloration may be cryptic (functioning as an adaptation allowing the prevention of prey detection); aposematic (functioning as a warning of unprofitability) or may be the result of sexual selection. Coloration may also be function in mimicry of other organisms. The subject may be investigated in terms of both chemical and physical basis of the colors (proximate cause) and the evolution of coloration (ultimate cause) Camouflage is generally viewed as the result of Natural Selection (Darwinism), and involves an organism's color blending in with its biotic (i.e. Moss) or abiotic (i.e. Sand) surroundings. This makes prey detection more difficult for predators. Camouflage is often accompanied by behavioral adaptations that make the most of it, such as landing areas of similar color, and aligning the body correctly (for the purpose of countershading for example) Such colors help predators (aggressive resemblance or anticryptic coloring) and prey (protective resemblance or procryptic coloring) Some small butterflies have eye-spots and fake antennae on hind wings that serve as Distraction or Deflection Patterns (distract prey, confuse prey) Examples: Hairstreak Butterflies (who use automimicry to misdirect predators by markings on the wings). This is an example of a distraction pattern Distraction patterns also come in the form of Startle patterns (ie moth's underwings). These patterns are often brightly colored part of an animal that is camouflaged to begin with (like the gray tree frog, with its bright yellow leggings; moths also have this). Startle the predator away from the prey If on display all the time, cannot be considered a distraction or startle pattern. An example of this is the Elater beetle Polyphemus = cyclops-like. ..Polyphemus moth, a giant silk moth, with the notable feature of the large, purplish eyespots on its two hindwings – startle pattern/distraction pattern Galls and gall insects: abnormal plant tissues, usually protruding as outgrowths. This is caused by various parasites, from fungi and bacteria, to insects and mites. Galls are often very organized structures and because of this, the cause of the gall can often be determined without the actual agent being identified. This applies particularly to some insect and mite galls. Example, galls on maples, usually have caterpillar and grubs, mites, etc.
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This note was uploaded on 08/13/2008 for the course BIOL 1902 taught by Professor Runtz during the Winter '08 term at Carleton CA.

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Lecture 2 - Lecture 2 Staying Alive: Animal Defences...

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