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BIOL 1902 (382)
Lecture 3

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Department
Biology
Course
BIOL 1902
Professor
Michael Runtz
Semester
Winter

Description
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. FISH –LATERAL 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, SHRUBS 2) OTHER ARMOUR - SPINES, THORNS, PRICKLES, STINGING HAIRS RASPBERRY, BLACKBERRY, CACTUS, THISTLE, HAWTHORN 3) TRICHOMES: SMALL HOOKED OR CLUBBED HAIRS = DENSE TANGLES IMPEDE SMALL ANIMALS - MITES, SMALL INSECTS; I.E., MULLEIN - SOME RELEASE STICKY GLANDULAR SECRETIONS = GLANDULAR HAIRS ONE TYPE - SEPARATELY STORED PHENOLS AND ENZYMES, WHEN ANIMAL BRUSHES THEM THEY BREAK OPEN, CONTENTS MIX LIKE EPOXY, CREATE GLUE-LIKE OOZE THAT HARDENS, ALSO RELEASES REPULSIVE CHEMICALS. 2) DIGESTIBILITY REDUCERS WHEN EATEN, MAKES IT HARD FOR THE ANIMAL TO DIGEST THE PLANT; MOST HAVE DUAL PURPOSE = STRUCTURAL AND DEFENSIVE FUNCTIONS A) DIGESTIBILITY REDUCERS THAT ARE STRUCTURAL ELEMENTS: PLANT TISSUES HAVE CELLS WITH STIFF WALLS THAT CAN BE THOUGHT OF AS REINFORCED CONCRETE - CEMENT WITH STEEL RODS STUCK IN FOR SUPPORT 1) CELLULOSE = STRUCTURAL ELEMENT; PECTIN AND HEMICELLULOSE = GLUEY CEMENT HOLDING “RODS” TOGETHER. TOGETHER THESE ELEMENTS GIVE RIGIDITY TO CELL WALLS BENEFIT: HARD TO DIGEST EVEN FOR INSECTS; OMNIVORES AND CARNIVORES DIGEST LITTLE, IF AT ALL. 2) LIGNIN = ANOTHER STRUCTURAL AGENT, ALSO IMPREGNATES AND STIFFEN CELL WALLS PROVIDES WOODINESS IN STEMS AND TOUGHENS LEAVES 3) SILICA = CELL WALLS STRENGTHENED BY SILICA, DERIVED FROM SILICON - ONE OF THE MOST COMMON ELEMENTS IN THE EARTH’S CRUST; SILICA IS FOUND IN GRASSES, HORSETAILS B) DIGESTIBILITY REDUCERS THAT ARE NOT STRUCTURAL 1) TANNINS - IMPORTANT AND COMMON IN WOODY PLANTS FREE OR STORED IN COMPARTMENTS; THEY ARE ASTRINGENT = TASTE DRY STORED SEPARATELY FROM PROTEINS IN CELLS WHEN LEAVES CHEWED, RELEASED AND BONDS TO PROTEINS CHANGES CONFIGURATION AND PREVENT DIGESTIVE ENZYMES FROM WORKING OFTEN MORE TANNINS IN OLDER LEAVES - CATERPILLARS STOP EATING WHEN BUILD UP 2) CALCIUM OXALATE CRYSTALS = IN LEAVES OF ARUM PLANTS: SKUNK CABBAGE AND JACK-IN-THE-PULPIT CALCIUM OXALATE IS CAUSTIC, HAS A CORROSIVE TASTE 3) ANTI-DIGESTIVE CHEMICALS: PROTEINASE INHIBITORS AFFECT DIGESTION BY BLOCKING THE ACTION OF PROTEINASE, THE ENZYME THAT DIGESTS PROTEINS IN ANIMALS. NOT ALWAYS PRESENT, SOMETIMES PRODUCED WHEN UNDER ATTACK. WOUND HORMONES ARE SENT OUT BY INJURED LEAF, GETS OTHER LEAVES ON THE PLANT TO PRODUCE THE INHIBITORS! SOME PLANTS UNDER ATTACK PRODUCE WOUND HORMONES THAT INDUCE PRODUCTION AND TRANSPORT OF PROTEINASE INHIBITORS (PREPARE FOR THE ATTACK, LOAD THE WEAPONS!) CHEMICAL DEFENCES: TOXINS TENS OF THOUSANDS OF TOXINS KNOWN; MANY PLANTS HAVE SEVERAL TYPES = COCKTA
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