Wk 3.doc

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29 Mar 2012
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WEEK 3 – TERMS AND EXAMPLES
ANIMAL DEFENCES CONTINUED:
BODYGUARDS: SOME ANIMALS ENLIST THE HELP OF MORE POWERFUL ANIMALS.
EXAMPLES: CARPENTER ANTS DEFEND APHIDS AND OTHER TYPES OF
SUCKING BUGS (SUCH AS TREEHOPPERS)
WHY? PAID FOR THEIR SERVICES WITH FOOD IN THE FORM OF HONEYDEW
VIGILANCE = BEING ON THE ALERT FOR DANGER. DETECTION OF DANGER INVOLVES VIGILANCE,
WHICH OFTEN INVOLVES SCANNING THE ENVIRONMENT FOR SIGNS OF DANGER.
ANIMALS SCAN FOR:
1) VIBRATIONS: CAN BE SENSED BY SOME ANIMALS
SNAKES – HAVE NO EARS; THEY SENSE VIBRATIONS IN THE GROUND.
FISHLATERAL LINES ON THEIR SIDES HAVE SENSORS FOR VIBRATIONS IN THE WATER
2) SCENTS: USING THEIR NOSES: OLFACTORY SENSE (SMELL) IS IMPORTANT
LARGE SNOUT HAS A LARGE NASAL CHAMBER WTH MANY FOLDS TO INCREASE ITS SURFACE AREA =
MORE OLFACTORY RECEPTORS, BETTER DETECTION OF ODOURS (MOOSE, DEER, ETC.)
VOMERONASAL ORGAN = JACOBSON’S ORGAN: SPECIAL POCKET IN ROOF OF MOUTH THAT HAS DENSE
CONCENTRATION OF SMELL RECEPTORS.
SNAKES ALSO HAVE THIS ORGAN. SNAKES HAVE FORKED TONGUES TO PINPOINT THE SOURCE OF THE
ODOUR
3) SOUNDS: AUDITORY SENSE = HEARING IS IMPORANT TO MANY ANIMALS. MAMMALS (MOOSE, DEER,
HARES) HAVE LARGE EXTERNAL EARS = LARGE AND MOBILE PINNAE TO CAPTURE SOUND LIKE
PARABOLIC DISHES.
SOME INSECTS HAVE SPECIAL EARS (THESE ARE ACTUALLY MEMBRANES THAT ARE SENSITIVE TO
SOUND)
MOTH EARS: TIGER MOTHS, HOOKTIP MOTHS HAVE MEMBRANES ON ABDOMEN FOR HEARING
BATS. WHEN MOTHS HEAR A BAT THEY CAN TAKE EVASIVE ACTION
MANTIDS ALSO HAVE “EARS”
DR. JAYNE YAK STUDIES INSECT HEARING AT CARLETON
4) MOVEMENT: VISUAL SCANNERS = EYES - CENTRAL EYE LOCATION ON SIDE OF FACE FOR BETTER
COVERAGE, GREATER COLLECTIVE FIELDS OF VIEW - RABBIT, DOVE = SEE 360 DEGREES
EYES ARE NOT ALWAYS CENTRAL ON SIDE OF FACE: AMERICAN BITTERN, AMERICAN
WOODCOCK – OTHER CONSTRAINTS ARE INVOLVED
MORE THAN TWO EYES CAN BE EVEN BETTER
FLOCKING -INCREASE VIGILANCE GIVING FLOCK MEMBERS MORE TIME TO FEED, PLUS SAFETY IN
NUMBERS. THERE ARE SINGLE-SPECIES FLOCKS AND MIXED-SPECIES FLOCKS OF BIRDS: THE TYPE OF
FOOD EATEN DETERMINES THE TYPE OF FLOCK THE BIRDS FORM
SELECTIVE PRESSURE FROM PREDATORS ON PREY SPECIES IS IMMENSE = NATURAL SELECTION =
MAJOR FORCE IN EVOLUTION
PLANT DEFENCES
CAN BE PHYSICAL, DIGESTIBILITY REDUCERS, CHEMICAL, EVEN BEHAVIOURAL
1) PHYSICAL DEFENCES
ALSO CALLED MECHANICAL PROTECTION
1) BODY ARMOUR = TOUGH EPIDERMIS ("OUTER SKIN") = BARK AND WOODY STEMS; TREES,
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