wk 13.doc

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29 Mar 2012
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TERMS AND EXAMPLES – FINAL LECTURE
SEED DISPERSAL IN PLANTS CONTINUED:
FORESTS HAVE PHYSICAL BARRIER OF TRUNKS AND LEAVES, THUS WIND NOT
PRESENT IN SUMMER
A) WIND IS AVAILABLE ONLY IN FALL, WINTER WHEN THERE ARE NO LEAVES
ON TREES (ONLY A FEW PLANTS EXPLOIT)
B) ANIMALS: SPRING EPHEMERALS SEEDS MATURE IN MID-SUMMER
(TRILLIUMS, VIOLETS, ETC.); SEEDS CONTAIN ANT
FOOD = ELAIOSOMES (PROTEIN PACKAGE ON SEEDS)
C) RAIN DROPS: USED TWO WAYS
A) SPLASH CUPS - MITREWORT
B) SPRING BOARD - FOAMFLOWER
D) VIOLETS ALSO USE BALLISTIC EJECTION = FORCIBLE EJECTION OF SEEDS
SOME PLANTS IN WET AREAS HAVE BALLISTIC EJECTION: JEWELWEED =
TOUCH-ME-NOT; SEEDS MATURE IN PODS THAT DEVELOP HIGH TENSION,
SPRING APART WHEN TOUCHED AND CATAPULT SEEDS UP TO 3 METRES FROM
PLANT
ADVANTAGES TO SEED DISPERSAL:
1) LESS CROWDING AND COMPETITON WITH PARENT NUTRIENTS, SOME LIGHT
2) IF PARENT DISEASE OR PARASITE, LESS CHANCE OF SPREADING TO YOUNG
AND VICA VERSA.
3) WHEN OFFSPRING MATURES, REDUCES CHANCE OF INBREEDING
I HOPE YOU HAVE SEEN THAT IN ALL ASPECTS OF THEIR
LIVES WILDFLOWERS AND OTHER PLANTS ARE MUCH,
MUCH MORE THAN A BUNCH OF PRETTY FACES!
PARENTAL INVESTMENT IN ANIMALS
PARENTAL INVESTMENT: INVESTING ENERGY AND RESOURCES INTO THE
PRODUCTION OF YOUNG AT THE RISK OF A PARENT NOT PRODUCING ANY
MORE YOUNG.
PARENTAL INVESTMENT CAN BE AN INVESTMENT INSIDE THE BODY (USUALLY
ONLY BY FEMALE), OUTSIDE BODY, BY ONLY FEMALE, BY BOTH MALE AND
FEMALE, OR BY A LARGER GROUP (WOLF PACKS FOR EXAMPLE).
PARENTAL CARE = PARENTAL INVESTMENT THAT IS GIVEN OUTSIDE OF THE
BODY
SEVERAL CONSIDERATIONS FOR PRODUCING YOUNG
1) NEED FAVOURABLE ENVIRONMENTAL CONDITIONS FOR THE YOUNG IE.
NOT TOO COLD; THIS IS THE REASON MOST YOUNG ANIMALS ARE HATCHED OR
BORN IN SPRING OR SUMMER
2) THERE MUST BE SUFFICIENT FOOD AVAILABLE TO FEED THE YOUNG
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3) YOUNG MUST HAVE SUFFICIENT TIME TO DEVELOP SO THAT THEY ARE
ADVANCED ENOUGH TO FACE ANY MAJOR ECOLOGICAL CHALLENGES (SO
THAT THEY CAN MIGRATE, STORE FOOD, WALK IN SNOW, ETC.
4) THE BIRTHING TIME MUST NOT INTERFERE WITH OTHER ESSENTIAL LIFE
STRATEGIES OF THE PARENTS, SUCH AS MIGRATION, STORING FOOD, OR MATING
TIMING IS NOT REALLY A PROBLEM FOR ANIMALS WITH SHORT
DEVELOPMENTAL PERIODS IE. INSECTS OR SMALL MAMMALS - MICE
PREGNANT A FEW WEEKS, YOUNG DEVELOP IN COUPLEOF WEEKS; OR BIRDS
MATE SPRING, YOUNG INDEPENDENT IN 1 MONTH
HOWEVER, AND OTHER LARGE MAMMALS - MANY HAVE LONG
DEVELOPMENTAL PERIOD INCLUDING GESTATION = INTERNAL PREGNANCY
PERIOD (MOOSE = 8 MONTHS); GREAT JUGGLING ACT TO ENSURE
YOUNGSTERS AND PARENTS NOT DISADVANTAGED
MUST MATE AT OPTIMAL TIME FOR ADULTS & GIVE BIRTH AT OPTIMAL TIME
FOR YOUNG: MOOSE MATE IN FALL, CALVES BORN IN SPRING; THEY ARE
DEVELOPED ENOUGH TO GET AROUND IN WINTER
BUT NOT ALL MAMMALS CAN DO THIS – THE BEST TIME FOR GIVING BIRTH
MAY PUT MATING TIME AT A POOR TIME OF YEAR FOR ADULTS AND VICE
VERSA
NOVEL SOLUTION:
DELAYED IMPLANTATION: DURING MATING, THE SPERM FERTILIZES THE
EGG BUT THE RESULTING EMBRYONIC BALL CALLED A BLASTOCYST DOES NOT
ATTACH TO THE UTERUS WALL; IT FLOATS AROUND IN SUSPENDED
ANIMATION. MONTHS LATER, WHEN IT IS A BETTER TIME FOR GESTATION, IT
IMPLANTS ON UTERUS WALL AND GESTATION (PREGNANCY) CONTINUES.
EXAMPLES: MANY CARNIVORES STRETCH OUT THE TIME BETWEEN
MATING AND GIVING BIRTH:
1) BLACK BEARS - MATE IN JUNE / JULY PREGNANCY 2.5 MO SHOULD BIRTH IN
SEPTEMBER BUT FALL STRESSFUL, THEN THEY PUT ON FAT FOR DORMANCY SO
DELAYED IMPLANTATION; FOR FIVE MONTHS ALLOWS THEM TO GIVE BIRTH IN
JAN OR FEB
2) FISHERS: MATE EARLY APRIL WITH A PREGNANCY OF ONE MONTH. THUS,
SHOULD GIVE BIRTH IN EARLY MAY BUT A DELAYED IMPLANTATION OF 11
MONTHS ALLOWS THEM TO GIVE BIRTH ALMOST A YEAR LATER IN LATE MARCH.
THIS MEANS THAT FEMALES MATE ONLY 10 DAYS AFTER GIVING BIRTH (THE
LITTLE RASCALS!)
DELAYED FERTILIZATION = SPERM STORAGE: BATS AND SOCIAL WASPS MATE
IN LATE SUMMER (OR FALL) AND STORE THE SPERM OVER THE WINTER,
RELEASING IT IN SPRING (AND SUMMER) TO FERTILIZE THE EGGS. THE EGGS ARE
NOT FERTILIZED WHEN THE ANIMALS MATE
.
ANMALS MUST ALSO ENSURE THAT THEIR YOUNG GET OFF
TO A GOOD START IN LIFE
IN ANIMALS WITH EXTERNAL FERT– FROGS, FISH, THERE IS A SMALL
INVESTMENT INTERNALLY, SMALL INVESTMENT EXTERNALLY
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