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Lecture 3

BIOL 1902 Lecture Notes - Lecture 3: American Woodcock, American Bittern, Major Force


Department
Biology
Course Code
BIOL 1902
Professor
Michael Runtz
Lecture
3

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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
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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
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