Biology 1B - Lecture 5: Interspecific Relationships




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PROFESSOR: HI EVERYONE. GOOD MORNING. GOOD TO SEE SO MANY OF YOU HERE

THIS MORNING
AFTER A HOLIDAY WEEKEND. THANK YOU FOR BRAVING THE

FOG AND THE COLD TO BE HERE. WE'RE GOING
TO JUMP RIGHT IN I

THINK. UNLESS YOU HAVE ANY BURNING LOGICAL QUESTIONS I CAN

HELP
WITH QUESTIONS FROM PREVIOUS LECTURES. I'LL BE REVIEWING A FEW THINGS IN THIS LECTURE
SO

HOPEFULLY I'LL ADDRESS THINGS YOU HAVE QUESTIONS ABOUT. BY ALL

MEANS COME BY OFFICE
HOURS, WE'RE HAVING A GOOD TIME THERE IF YOU

WANT TO ASK EXTRA QUESTIONS IN OFFICE HOURS.
BUT ANYTHING, ANYTHING ON COURSE

LOGISTICS I CAN HELP WITH RIGHT NOW. YES?

STUDENT:
DO WE HAVE DISCUSSIONS THIS WEEK?

PROFESSOR: YOU DO HAVE DISCUSSIONS THIS WEEK, CORRECT?
ALL: NO. [LAUGHTER]

PROFESSOR: THAT ANSWERS THAT. RIGHT. OKAY. WHEN YOU HAVE A HOLIDAY
DAY OFF, EVERYTHING

IS CANCELED. SO AMAZINGLY YOU'RE STILL, IT'S BEEN SUCH A

GRADUAL ENTREE
INTO THIS COURSE, WHICH IS NICE. BUT STARTING NEXT WEEK

IT'S GOING TO GET REALLY BUSY
FOR YOU. I WANT YOU TO BE

PREPARED. I DON'T WANT YOU TO BE SURPRISED BY THE PACE ONCE
THIS CLASS ACTUALLY GETS GOING. BUT NO, NO DISCUSSIONS THIS

WEEK, NO LABS THIS WEEK.
SO YOU'RE STILL EASING IN.

OKAY. I SHOULD GET RIGHT IN. I HAVE A LOT OF SLIDES.

CELL
PHONES OFF. INCLUDING MINE.

OKAY. WE'RE TALKING ABOUT INTERSPECIFIC RELATIONSHIPS
PRIMARILY TODAY. RELATIONSHIPS BETWEEN SPECIES. AND THIS WILL

BE THE FOUNDATION FOR US FOR
OUR LOOK AT COMMUNITY ECOLOGY. SO





WE WILL SET UP OUR CATEGORIZATION SCHEME
FOR THE TYPES OF

INTERSPECIFIC RELATIONSHIPS THAT EXIST. AND WE'LL FOCUS IN TURN

ON COMPETITION
AND PROVIDE SOME EXAMPLES OF COMPETITION FROM

FIELD STUDIES. WE WILL MODIFY OUR EQUATIONS
FOR LOGISTIC GROWTH

FROM LAST TIME IN SHOWING HOW COMPETITION BETWEEN SPECIES CAN BE

MODELED
MATHEMATICALLY. WE WILL THEN FOCUS ON PREDATION

ANOTHER MAJOR TYPES OF ECOLOGICAL INTERACTION.
AND SUBSUMING UNDER THIS

HERBIVORY, NOT DRAWING A DISTINCTION BETWEEN PREDATION, WHERE
ONE CREATURE CONSUMES ANOTHER CREATURE. AND IN TALKING ABOUT

PREDATION WE'LL TALK A
BIT ABOUT PREDATOR-PREY CYCLES IN THE

CONTEXT OF OUR STUDIES OF POPULATION GROWTH. AND THEN,
YEAH, WE

WILL TALK ABOUT HERBIVORY SEPARATELY FROM THAT. DRAWING OUT THE

SIMILARITIES
MORE THAN DIFFERENCES WITH PREDATION. AND THEN FINISHING MOSTLY

WITH JUST PICTURES
AND STORIES CONCERNING MUTUALISM AND

COMMENSALISM.

BEFORE I REVIEW A COUPLE OF THINGS FROM THE
LAST LECTURE,

LET'S INTRODUCE THE CATEGORIES WE'RE GOING TO BE DEALING

WITH TODAY. IN
OUR CLASSIFICATION OF INTERSPECIFIC INTERACTIONS

YOU CAN CLASSIFY SUCH INTERACTIONS IN VARIOUS
WAYS. AND NONE OF

THEM ARE PERFECT. NONE OF THEM IS PERFECT. WE WILL FOCUS ON

THE
EFFECTS OF THESE INTERACTIONS ON THE PARTICIPANTS AS A MEANS

FOR CLASSIFYING THE TYPE OF INTERACTION.
SO WE WILL DISTINGUISH

COMPETITION FROM PREDATION AND HERBIVORY FROM COMMENSALISM
AND

MUTUALISM. AS I JUST SAID, THE CATEGORIES ARE DISTINGUISHED

BASED ON WHETHER THEY
HAVE A NEGATIVE, A POSITIVE, OR A NEUTRAL





EFFECT ON THE PARTICIPANTS. AND WE'LL
JUST USE A PLUS AND A

MINUS AND A ZERO IF YOU WANT TO INDICATE POSITIVE INFLUENCE,
NEGATIVE INFLUENCE NO INFLUENCE.

AND WITH REGARD TO AN INFLUENCE ON A SPECIES, WHAT
MIGHT I

BE REFERRING TO? A POSITIVE INFLUENCE OR A NEGATIVE INFLUENCE?

INFLUENCING WHAT
ABOUT A SPECIES OR A POPULATION OF AN ORGANISM? NUMBER OF

INDIVIDUALS, IF YOU'RE TALKING
POPULATION, PERHAPS. REPRODUCTIVE SUCCESS,

IF YOU'RE TALKING ABOUT AN INDIVIDUAL, PERHAPS.
RATE OF GROWTH, IF YOU'RE

TALKING ABOUT AN INDIVIDUAL WHICH SHOULD REFLECT THE SUCCESS
OF

THAT INDIVIDUAL AND ULTIMATELY ITS REPRODUCTIVE OUTPUT.
STUDENT: LONGEVITY?

SO YOU HAVE THE IDEA ABOUT THESE POSITIVE AND NEGATIVE EFFECTS.
SO WE'LL START THE FOCUS ON COMPETITION, IN PART BECAUSE

COMPETITION HAS BEEN A MAJOR
FOCUS OF ECOLOGICAL STUDIES SINCE

DARWIN WITH INCREDIBLE DEBATE. AND SWINGS OF THE
PENDULUM IN

TERMS OF THE RECOGNITION OF ITS IMPORTANCE OR ITS DE-EMPHASIS,

IT'S
LACK OF IMPORTANCE IN NATURE. BERKELEY HAS BEEN AN

INSTITUTION THAT HAS FOCUSED A LOT
ON THE STUDY OF COMPETITION.

AND BY ALL ACCOUNTS COMPETITION IS REAL AND OCCURS IN
NATURE.

BUT JUST REALIZE THAT ECOLOGISTS VARY A LOT IN THE DEGREE TO

WHICH THEY CONSIDER
IT AS A MAJOR STRUCTURING FACTOR IN NATURE.

IT HAS A LONG HISTORY OF STUDY OF COMPETITION.
GOING BACK TO

DARWIN, YES. BUT IT REALLY TOOK OFF WITH SOME OF THE WORK OF THE

GAUSE.
IN THE '30S. IN THE 1930S IN PARTICULAR. LABORATORY

STUDIES PRIMARILY THAT LENT THEMSELVES TO
THEORETICAL INSIGHTS.

AND EVEN PHILOSOPHICAL INSIGHTS ABOUT NATURE THAT PROVIDED



FOUNDATIONS FOR LATER STUDY IN BOTH LAB AND FIELD. AND IN

THEORY. SOME OF GAUSE'S ORIGINAL
DATA THERE CLEANED UP A BIT

FOR MORE GENERAL CONSUMPTION. WE CAN LOOK AT THEM HERE. HE'S
LOOKING AT PARAMECIA IN THE LABORATORY, GROWING GROWING TWO DIFFERENT SPECIES OF PARAMECIA
IN ISOLATION AND THEN TOGETHER. DID I ENLARGE MY CURSOR?

NOT SO MUCH, BUT YOU CAN SEE
IT. FOCUSING ON THESE CURVES.

THESE CURVES ARE OF SIGMOID SHAPE, RIGHT? LET'S JUST USE
THIS

OPPORTUNITY TO REVIEW A MINUTE FROM WHAT HAPPENED WAY BACK LAST

WEEK. SO IF
THE LIGHTS COULD COME UP A MOMENT? THANK YOU. LET'S JUST REVIEW A BIT

ON POPULATION GROWTH
AND OUR MODELING WORK FROM LAST TIME. RECALL

THAT IN THE ABSENCE OF RESOURCE LIMITATIONS,
A POPULATION AS A

RESULT OF ITS OWN INTRINSIC CAPACITY TO INCREASE OVER TIME IN

TERMS
OF ITS NUMBERS
WILL INCREASE GEOMETRICALLY OR

EXPONENTIALLY, RIGHT? SO WE REFER TO THIS AS GEOMETRIC INCREASE
OR

EXPONENTIAL INCREASE. AND WE MODELED IT, RIGHT, IT'S IN THE

SHADOWS HERE. AS
DNDT EQUAL TO R, THE INTRINSIC RATE OF INCREASE PER

CAPITA RATE OF GROWTH TIMES N. AND IT
STEEPENS WITH TIME BECAUSE N IS

BECOMING LARGER, SO HAVE A COMPOUNDING OF THE

GROWTH
RATE. JUST LIKE YOU WOULD HAVE A COMPOUNDING OF THE

INTEREST IN THE YOUR BANK ACCOUNT
IF YOU LEFT AN INITIAL SUM IN

THERE. THE GROWTH, THE INTEREST ON YOUR INITIAL SUM YEAR
AFTER

YEAR WILL GROW AS A RESULT OF THE GROWING BASE OF MONEY IN THE

BANK ACCOUNT.
THE SAME WAY A POPULATION WILL GROW, THE

GROWING NUMBER OF INDIVIDUALS WILL PROVIDE
A LARGER BASE. AND R

TIMES N AS A RESULT WILL INCREASE MORE STEEPLY WITH TIME. SO



THAT'S MOST BASICALLY WHAT WE UNDERSTAND WITH GEOMETRIC INCREASE.

AND THERE ARE PLENTY
OF EXAMPLES OF THAT IN THE LAB AND IN NATURE. BUT THIS

CANNOT CONTINUE FOREVER, OF COURSE.
THERE ARE LIMITS TO GROWTH.

AND THESE LIMITS TO GROWTH ACT SUCH THAT POPULATION GROWTH
THROUGH TIME, SAME AXES HERE, IS FREQUENTLY SEEN TO SLOW AND TO

LEVEL OFF. SPEAKING IDEALLY. THINGS ARE OFTEN MUCH NOISIER
THAN THIS. MORE COMPLICATED THAN THIS. STILL MODELABLE

BUT RARELY SO SIMPLE. AND YET
THERE ARE PLENTY OF EXAMPLES.

PARTICULARLY IN LAB SETTINGS IN THIS TYPE OF SIGMOIDAL,
OR SIGMOID GROWTH. THIS IS THE

LOGISTIC CURVE, LOGISTIC MODEL. WHERE AT SOME POINT
HERE, THE EFFECTS OF THE

LIMITATIONS OF THE ENVIRONMENT ACT ON THE GROWING POPULATION
TO

LIMIT ITS NUMBERS IN TIME. WE MODEL THIS WITH THE ADDITION

OF AN EXTRA TERM TO OUR
EXPONENTIAL GROWTH MODEL. RIGHT? AND THAT'S JUST

WITH REFERENCE TO THE CARRYING CAPACITY,
K. WHICH WE CALLED

K. WHICH IS WITH REFERENCE TO THE EXISTING POPULATION UNDER

STUDY,
THE CARRYING CAPACITY IS THE TOTAL NUMBER OF INDIVIDUALS

OF THAT POPULATION IN THAT
ENVIRONMENT LOCALLY AT THAT TIME THAT

CAN BE SUPPORTED. IT'S ALWAYS CONTEXTUAL, TO CARRYING
CAPACITY.

THE CARRYING CAPACITY FOR ANTS ON THE BERKELEY CAMPUS IS SOME

THEORETICAL
NUMBER RIGHT NOW. BUT AT A DIFFERENT SEASON THAT

CARRYING CAPACITY MIGHT CHANGE AND
IT WILL CHANGE. AND 20 YEARS

NOW, GIVEN THE CHANGES IN THE ENVIRONMENT WITH A, WITH
DIFFERENCES IN OTHER ORGANISMS THAT LIVE HERE AND CLIMATE, THE

CARRYING CAPACITY IS LIKELY
TO BE DIFFERENT AGAIN. AND THE

CARRYING CAPACITY OF ANTS HERE IS DIFFERENT FROM THE
CARRYING





CAPACITY OF ANTS ON ANOTHER UNIVERSITY CAMPUS. IN SPACE IT

DIFFERS.
CARRYING CAPACITY IS ALWAYS WITH REFERENCE TO

PARTICULAR PLACES AND PARTICULAR TIMES.
BUT WE CAN MODEL THIS TYPE OF SIGMOIDAL GROWTH WELL WITH

THIS SIMPLE EQUATION. AND WHAT
YOU NEED TO DO IF YOU HAVEN'T

ALREADY IS UNDERSTAND HOW THE EFFECT OF THIS TERM CAME,
MINUS N

OVER K, PRODUCES THIS GRADUAL APPROACH TO AN ASYMPTOTIC APPROACH

TO THE CARRYING
CAPACITY. AND LET ME GIVE YOU, IF YOU HAVEN'T

DONE IT ALREADY, WE HAD A COUPLE OF GEE WHIZ
MOMENTS IN OFFICE

HOURS WHERE PEOPLE STARTED TO SEE JUST HOW THAT WORKS. AND IT

REALLY
IS AN ESTHETICALLY SATISFYING MODEL. I REALLY HOPE YOU WILL

ARRIVE AT THAT UNDERSTANDING.
SO I JUST WOULD LIKE TO SUGGEST

ONE WAY TO DO THAT. SO LET'S ASSUME, LET'S ASSUME
A FIXED

INTRINSIC RATE OF INCREASE PER CAPITA GROWTH RATE OF ONE FOR

SIMPLICITY. LET'S
ASSUME R EQUALS ONE. LET'S ASSUME OUR

CARRYING CAPACITY, LET'S CHANGE IT FROM ANTS TO RABBITS,
JUST FOR FUN, IS A

HUNDRED RABBITS IN THIS SETTING THAT WE'RE TALKING ABOUT. SAY

DOWN
AT THE MARINA, IN THE PARK DOWN IN THE MARINA WHERE THEY

HAVE A BUNCH OF JACK RABBITS
NOW THAT THEY'VE RESTORED THE LAND TO MORE NATURAL CONDITIONS.

A HUNDRED JACK RABBITS
CAN LIVE DOWN THERE AND THEY HAVE AN R OF ONE. WHEN THAT LAND

WAS RESTORED DOWN THERE,
AND I CAN ALSO SEE I'M GOING TO RUN OUT

OF ROOM HERE, WHEN THAT LAND WAS RESTORED
AT THE MARINA, THERE

WAS ONLY ONE RABBIT. AND IF THERE WERE ONLY ONE RABBIT, WHAT
WOULD OUR TERM K MINUS N OVER K BE? IF K EQUALS 100?

99 OVER 100, RIGHT? WHICH IS CLOSE
TO ONE. .99. SO





WHEN THAT TERM IS VERY HIGH LIKE THAT, CLOSE TO ONE, THIS
EQUATION IS BASICALLY GOING TO GO TO RN, THE EXPONENTIAL.

YOU'RE GOING TO SEE EXPONENTIAL
GROWTH WHEN THE POPULATION NUMBER IS

VERY, VERY LOW, LIKE ONE. IF IT GOES UP TO 50, IF
YOU HAVE 50 RABBITS

AFTER A CERTAIN AMOUNT OF TIME, WHAT WILL K MINUS N OVER K EQUAL?
EQUAL A HALF, RIGHT? .5. AND THAT WILL HAVE A HALVING EFFECT

ON R TIMES N WHICH WILL
LEAD TO THIS SLOWING OF GROWTH. YOU CAN

FOLLOW THAT OUT. YOU CAN FOLLOW IT OUT ALL
THE WAY TO 99 WHERE

YOU HAVE THE TERM GO TO 0.01. RIGHT? RADICALLY SLOWING THE

GROWTH
AS IT APPROACHES THE CARRYING CAPACITY THERE. REMEMBER

CARRYING CAPACITY IS 100 SO YOU'RE
ALMOST THERE. OR TO A

HUNDRED ITSELF. AND AT A HUNDRED YOU'RE GOING TO HAVE A HUNDRED
MINUS A HUNDRED IN THE NUMERATOR. RIGHT? SO CHANGE NUMBERS OVER TIME,

ZERO, GROWTH WILL
CEASE. SO YOU CAN SEE THAT. YOU SHOULD BE ABLE TO
IF YOU JUST WORK THROUGH IT A COUPLE OF TIMES. POPULATION

DYNAMICS ARE USUALLY MUCH MORE
COMPLICATED. WE PRESENT THE

SIMPLE CASE INITIALLY. TO BUILD ON. AND MODELERS DO MAKE
MORE

COMPLEX THESE, THE MATHEMATICS HERE TO BETTER FIT THE REALITY OF

NATURAL POPULATION.
BUT WE'LL STOP AT THIS POINT FOR OUR

PURPOSES REALLY IN MODELING THE GROWTH OF INDIVIDUAL
POPULATIONS.

I THINK I MENTIONED THAT IN A PREVIOUS LECTURE THAT SOME OF

WHAT I WAS
DOING WAS DUMBED DOWN. AND SOMEONE ASKED ME

AFTERWARDS ARE YOU REALLY DUMBING IT DOWN
IN HERE? AND I AM DUMBING IT DOWN.

THAT'S, BUT THAT'S THE NATURE OF INTRODUCTORY SCIENCE.
IT'S THE

NATURE OF LEARNING ANY SKILL REALLY. AS YOU LEARN, YOU LEARN THE

BASICS, THE
FOUNDATIONS ON WHICH TO BUILD AND THEN HOPEFULLY AS





YOU BECOME MORE EXPERIENCED, YOU
START TO CHALLENGE AND ERODE

THOSE FOUNDATIONS AS YOU ADVANCE. SO I THINK THAT'S JUST FINE,
WE ARE PRODUCING SOMETHING SIMPLE. AND IN SOME WAYS MAY BE

WRONG BECAUSE THINGS HAVE
ADVANCED BEYOND I DON'T UNDERSTAND THAT.

BUT YOU NEED TO LEARN THE BASICS SO YOU CAN
LEARN HOW THESE

THINGS ARE SIMPLE OR WRONG OR SHOULD BE CHALLENGED.

ALL RIGHT. SO BACK
TO GAUSE. WHEN HE GREW PARAMECIA IN

ISOLATION, THEY DID FOLLOW A ROUGHLY SIGMOID GROWTH CURVE.
BUT

IN GROWING THEM TOGETHER, ONE SPECIES WAS SEEN TO PERSIST WHEREAS

THE OTHER WENT
TO LOCAL EXTINCTION. AND GAUSE INTERPRETED THIS

AS IN TERMS OF A COMPETITIVE SUPERIORITY
OF THE ONE SPECIES IN

RELATION TO THE OTHER. THIS LED HIM TO WHAT BECAME KNOWN AS THE
COMPETITIVE EXCLUSION PRINCIPLE.
THE IMPORTANCE OF THIS ONLY WAS DRAWN

OUT OVER TIME. AND YOU CAN FIND VARIOUS DEFINITIONS
OF IT.

ONE DEFINITION THAT PRODUCES A COUNTERPOINT TO WHAT'S GIVEN IN

YOUR BOOK, IF TWO COMPETING
SPECIES COEXIST IN A STABLE

ENVIRONMENT, THEY DO SO AS A RESULT OF ECOLOGICAL

DIFFERENTIATION.
AND IT'S BEEN A VERY POWERFUL PRINCIPLE IN

STRUCTURING ECOLOGICAL THOUGHT AND ECOLOGICAL
EXPERIMENTS. BUT

PLEASE DO REALIZE THAT THE IMPORTANCE OF IT IN NATURE IS HOTLY
DEBATED.

SO LET'S FOCUS ON COMPETITION. YOU WANT A DEFINITION,

COMPETITION IS AN
INTERACTION BETWEEN ORGANISMS BASED ON A SHARED

REQUIREMENT THAT IS IN LIMITED SUPPLY. YOU
DON'T COMPETE FOR

SOMETHING IF IT'S NOT IN LIMITED SUPPLY. WE DON'T TEND TO




COMPETE FOR OXYGEN, WE HUMAN INDIVIDUALS. MOST PARTS OF THIS

PLANET. RIGHT NOW THERE'S
ENOUGH. AND WE DON'T TEND TO BATTLE

ONE ANOTHER FOR IT. IN SOME AREAS WE DO COMPETE
FOR, SAY,

WATER. WHICH IS IN VERY SHORT SUPPLY, FRESH WATER IN MANY PLACES.

AND
COMPETITION CAN BE REAL AND SOMETIMES FIERCE OR SUBJECT TO --

BUT LET'S DISTINGUISH TYPE
OF COMPETITION. INTERFERENCE

COMPETITION FROM EXPLOITATIVE COMPETITION. WHEN YOU THINK
OF

INTERFERENCE COMPETITION THINK OF A BEHAVIORAL INTERACTION THAT

CAUSES A PHYSICAL INTERACTION.
SO THINK OF DIRECT PHYSICAL

INTERACTIONS BETWEEN INDIVIDUALS. EXAMPLES GIVEN HERE OF
A

COUPLE OF BEETLES VYING FOR POSITION, PERHAPS VYING FOR POSITION

IN RELATION TO
MATING OPPORTUNITIES. LOOKING HERE AT A LION AND

A HYENA. IF YOU THOUGHT CATS AND DOGS
DIDN'T LIKE EACH OTHER,

TRY LIONS AND HYENAS. THEY REALLY DON'T LIKE EACH OTHER. AND

THEY
WILL BATTLE SOMETIMES TO THE END. AND IN A COMPETITIVE

SPIRIT AS A RESULT OF THAT.
USUALLY COMPETITION FOR FOOD.

THEY EAT SIMILAR THINGS. THERE ARE DIFFERENCES THAT ARE VERY
REAL WHERE LIONS FOCUS SOMEWHAT MORE ON THE SOFT TISSUES OF PREY.

THE HYENAS WILL ALSO
CONSUME THE HARD TISSUES, THE BONES. THE

HYENA MIGHT SCAVENGE AFTER A LION HAS MADE
A KILL. THEY'RE,

THEY WILL NOT JUST EAT THE BONES AND HOOVES BUT WILL EAT ALL POO
AND PREVIOUS THINGS THAT THE OTHERS HAVE LEFT BEHIND. THERE ARE

DIFFERENCES THAT DO EXIST.
REAL ECOLOGICAL DIFFERENCES BUT THE

COMPETITION IS REAL ENOUGH THAT WHEN THEY ENCOUNTER EACH
OTHER

THERE'S SOME KIND OF DIRECT CONFLICT. THEY CAN'T GET TOO




CLOSE TO EACH OTHER.
INTERFERENCE COMPETITION, BETWEEN TWO

SPIDERS. BUT WHAT IS COMPETITION FOR? SOME RESOURCE
IN LIMITED

SUPPLY, IT MIGHT FOOD. IT MIGHT BE MATING OPPORTUNITIES. IT

MIGHT BE A SPACE
IN WHICH TO NEST, OR DWELL. IT MIGHT BE WATER. IT MIGHT BE NUTRIENTS.

SO WE SPEAK OF IT
BROADLY, COMPETITION. IN EXPLOITATIVE COMPETITION, THE PARTICIPANTS MAY NOT

ENCOUNTER EACH
OTHER AT ALL. THAT'S WHAT'S MEANT TO BE IMPLIED

BY THIS DIAGRAM WHERE IN THIS CASE TWO CONSUMERS,
A CATERPILLAR

AND A GRASSHOPPER ARE BOTH LEAF CONSUMERS. THEY'RE BOTH

CONSUMING LEAVES
BUT PERHAPS THEY DON'T EVER REALLY PHYSICALLY

ENCOUNTER EACH OTHER. BUT THEY'RE CONSUMING
THE SAME STUFF, SO

LIMITING THE RESOURCE AVAILABLE TO THE OTHER BY THEIR OWN

ACTIVITIES.
AS A RESULT THEY'RE COMPETING BECAUSE THEY'RE

REDUCING THE RESOURCE THAT'S AVAILABLE TO
THE OTHER PARTICIPANT

EVEN THOUGH NOT PHYSICALLY ENCOUNTERING EACH OTHER.

EXPLOITATION OF
THE COMMON RESOURCE, THEY COMPETE.

HERE YOU HAVE A TANGLE OF ROOTS. IN A BANK OF
SOIL. WHAT KIND OF COMPETITION MIGHT YOU SEE HERE?

INTERFERENCE OR EXPLOITATIVE? I HEARD
BOTH. I THINK YOU COULD

SEE BOTH AMONG THESE PLANTS. THE ROOTS MIGHT PHYSICALLY TRY TO
OCCUPY SPACE TO THE EXCLUSION OF OTHER ROOT SYSTEMS. AND THEN

SEEKING SIMILAR NUTRIENTS
OR WATER THEY MAY REDUCE THE AVAILABLE

SUPPLY OF RESOURCES TO ALL THE OTHER PARTICIPANTS.
SO YOU CAN

HAVE INTERFERFENCE AND EXPLOITATION, THEY'RE NOT MUTUALLY

EXCLUSIVE. THIS IS
A GOOD POINT TO INTRODUCE THE CONCEPT OF A

NICHE. HOPEFULLY I'LL HAVE MORE TIME TO LOOK
AT THE HISTORY OF




THIS CONCEPT A LITTLE BIT BECAUSE IT'S VERY INTERESTING,

STRETCHING
BACK TO THE FOUNDER OF OUR MUSEUM HERE. THE MUSEUM

OF VERTEBRATE ZOOLOGY. JOSEPH GRENNEL
WAS ONE OF FIRST PEOPLE TO

FORMALLY DEFINE THE NICHE. AND LATER ECOLOGISTS SUCH AS
CHARLES ELTON AND G. EVELYN HUTCHINSON BUILT UPON THAT AND HOPEFULLY I'LL HAVE MORE TIME
TO TALK ABOUT

THAT WHEN WE TALK ABOUT COMMUNITIES. BUT HERE, THESE CLASSIC

STUDIES PRIMARILY
OF JOSEPH CONNELL FROM THE '60S HELPED TO

ILLUSTRATE THE COMPETITION AND THE IDEA OF
A NICHE. AND THE

DISTINCTION BETWEEN A FUNDAMENTAL NICHE AND A REALIZED NICHE. GOOD

EXAMPLE
FROM YOUR BOOK. YOUR BOOK TENDS TO DO VERY WELL IN THIS

SECTION. SO WE HAVE TWO TYPES
BARNACLES. THEY GROW ON SOLID

SUBSTRATE. PREFLOATING AS LARVAE AND WHEN ANCHORED, FORM
A SHELL

AROUND THEM AND HARDEN ONTO THE SUBSTRATE. THEN THEY'RE

IMMOBILE. IN THIS
AREA, IN THIS REGION WHERE THE OCEAN PICTURED

HERE RISES ALL THE WAY TO A HIGH TIDE LEVEL
AT THIS POINT AND ALL

THE WAY DOWN TO A LOW TIDE LEVEL AT THIS POINT. WE HAVE TWO
SPECIES, TWO GENRE, THE BARNACLE, CHTHAMALUS AND BALANUS GROWING

IN SPECIAL PARTS OF
HABITAT WITH CHTHAMALUS GROWING ALL THE WAY

UP TO THE HIGH TIDE LINE AND BALANUS ALL THE
WAY DOWN TO THE LOW

TIDE LINE. IT WAS POSSIBLE TO STUDY THE FUNDAMENTAL RESOURCES

AND TOLERANCES
OF THESE ORGANISMS TO DIFFERENT ENVIRONMENTAL

FACTORS THROUGH A MANIPULATION EXPERIMENT.
HERE'S WHAT WE JUST

SAW. IT'S THE SAME PICTURE AS BEFORE REALLY, JUST SIMPLIFIED A

LITTLE
BIT. HERE WHAT WE SEE REALIZED IN NATURE IS THIS

CONFIGURATION. WITH CHTHAMALUS OCCUPYING
THE UPPER REGION AND




THE BALANUS THE LOWER. AND NATURE OF THESE ORGANISMS, THE
SPATIAL AND PHYSICAL ENVIRONMENTAL SPACES THAT THESE ORGANISMS

COME TO OCCUPY IN THE
FACE OF NATURAL CONDITIONS. WHEN

CHTHAMALUS WAS REMOVED, THE BLUE BARNACLE FROM THE LOWER
REGION,

WHEN BALANUS WAS REMOVED CHTHAMALUS CAME TO OCCUPY THE REGION.

MOVED INTO THE
TERRITORY THAT WAS PREVIOUSLY OCCUPIED BY BALANUS.

IF YOU REMOVE THE CHTHAMALUS, BALANUS
DOESN'T BUDGE, IT REMAINS

IN THE SAME SPATIAL CONFIGURATION. THROUGH MANIPULATION STUDY
WHERE YOU ACTUALLY REMOVE ONE SPECIES OR THE OTHER, YOU COME TO

SEE THAT THE FUNDAMENTAL
NICHES OF THESE ORGANISMS SEEM TO

DIFFER. THE FUNDAMENTAL NICHE IN THE SENSE THAT THE
BROADEST

POSSIBLE ZONE OF OCCUPATION IN THE ENVIRONMENT THAT AN ORGANISM

CAN OCCUPY
IN THE ABSENCE OF COMPETITION AND OTHER FACTORS, THE

FUNDAMENTAL NICHE OF THE CHTHAMALUS
IS THE ENTIRE REGION BETWEEN LOW AND HIGH TIDE LINES
AS EVIDENCED BY THE REMOVAL EXPERIMENT THAT TOOK BALANUS OUT WHERE IT CAME TO OCCUPY THAT
WHOLE
REGION. BUT BALANUS ON THE

OTHER HAND, ITS REALIZED NICHE IS EQUIVALENT TO ITS FUNDAMENTAL
NICHE. IT DIDN'T BUDGE IN THE ABSENCE OF THIS APPARENT

COMPETITOR. SO WE MUST REALIZE
THAT WHAT WE SEE IN THE NATURAL

WORLD IS A REFLECTION OF DYNAMICS BETWEEN EXISTING
POPULATIONS.

AND IN THE ABSENCE OF COMPETITORS, THE DISTRIBUTION AND ABUNDANCE

OF A PARTICULAR
POPULATION MIGHT DIFFER VERY MUCH. SO I WON'T FOCUS ON THIS FOR LONG. LET'S NOTE

THAT
THIS IS OUR SIMPLE LOGISTICAL MODEL, RIGHT, WITH THIS EXTRA TERM.

IF YOU TAKE THIS EXTRA
TERM OUT YOU'LL HAVE YOUR LOGISTIC MODEL.

WHAT WE WANT TO SHOW HERE IS HOW YOU CAN MODEL
THE COEXISTENCE OF

TWO POPULATIONS OF COMPETITION. THEY'RE CALLED THE

LOTKA-VOLTERRA EQUATIONS.
NAME AFTER AN AMERICAN AND ITALIAN





WHO SIMULTANEOUSLY DERIVED THESE EQUATIONS
FOR THE STUDY OF NATURAL POPULATIONS.
IT'S NAMED AFTER THEM. THEY USED THEM ALSO FOR STUDIES

OF PREDATOR-PREY DYNAMICS. BUT
HERE WE'RE FOCUSED ON COMPETITION. JUST KNOW WHAT WE'RE DOING. YOU

CAN FURTHER DISCUSS
THIS IN DISCUSSION SECTIONS.

I DON'T THINK THIS IS ADDRESSED IN YOUR BOOK. WE NEED A
TERM TO MODEL THE EFFECT OF A SECOND SPECIES ON OUR FIRST

SPECIES, REPRESENTED BY N SUB
1. WE NEED TO CALCULATE THIS

EFFECT OF THE SECOND SPECIES IN TERMS OF THE NUMBERS OF
INDIVIDUALS OF THE FIRST SPECIES. WE DO THAT JUST USING A

COEFFICIENT, A COMPETITION
COEFFICIENT, ALPHA, TO REPRESENT THE

PROPORTIONAL EFFECT THAT A SECOND SPECIES HAS ON THIS FIRST
SPECIES. AND IN THE SAME WAY, WE USE THE COMPETITION

COEFFICIENT DATA TO REFLECT THE EFFECT OF
THE FIRST SPECIES BACK

ON THE SECOND SPECIES TO MODEL THE DYNAMICS OF THAT SECOND

SPECIES
IN TIME. AND THE RELATIVE EFFECTS OF ONE SPECIES ON

ANOTHER MIGHT DIFFER QUITE A LOT. ONE
SPECIES MIGHT HAVE A VERY

STRONG COMPETITIVE EFFECT ON THE SECOND SPECIES WHERE THE OTHER
MAY HAVE A VERY LITTLE EFFECT. AND THAT'S SOMETHING THAT CAN

ALSO BE EMPIRICALLY DERIVED
IN NATURE. YOU CAN CONDUCT STUDIES

IN NATURE TO DERIVE ACTUAL VALUES, REAL WORLD VALUES
FOR THESE

COEFFICIENTS. IF YOU KNOW ONE SPECIES HAS A VERY STRONG

COMPETITIVE EFFECT
ON THE OTHER, YOU WANT TO MODEL THE

COMPETITIVE COEFFICIENT AS VERY HIGH, AS .9 SAY. SO .9
TIMES THE

NUMBER OF INDIVIDUALS IN THAT POPULATION IS GOING TO PRODUCE A

RELATIVELY
LARGE NUMBER TO PLUG INTO THIS EQUATION. AND YOU CAN

FOLLOW THE LOGIC IN THE MODEL OF
THE LOGISTIC CURVE, THE EFFECT





THAT THAT WOULD HAVE. I DON'T WANT TO SPEND TOO
MUCH MORE TIME

ON THIS. IT STRETCHES BEYOND THE LIMITS OF WHAT YOU NEED TO KNOW

HERE
IN TERMS OF OUR MODELING EQUATIONS. I WOULDN'T PROVIDE ANY

FURTHER COMPLEXITY TO THESE
EQUATIONS.

SO LET'S LOOK AT EXAMPLES OF INTERSPECIFIC RELATIONSHIPS IN

NATURE THAT
SEEM TO HIGHLIGHT COMPETITION RELATIONSHIPS. AND

ONE EXAMPLE COMES FROM SOMETHING THAT'S
VERY OFTEN SEEN, IT'S

VERY OFTEN SEEN IN THE ORGANISMS THAT I'M MOST INTERESTED IN,
IN

BIRDS AND MOUNTAINS AS WELL AS LIZARDS. AND OTHER BIRD GROUPS.

THE FACT OF RESOURCE
PARTITIONING, WHERE THE DIFFERENT SPECIES OF

A GROUP, OFTEN A CLOSELY RELATED GROUP,
LIKE A GENUS OF LIZARDS

HERE, ANOLIS LIZARDS OCCUPY DIFFERENT PARTS OF THE HABITAT. IN
THIS CASE DIFFERENT VISIBLE PARTS OF THE HABITAT. A. RICORDII

IS UP IN THE TREES. A. DISTICHUS
IN THE FENCE POST.

IN THE LOWER PORTIONS OF VEGETATION, A. CHRISTOPHEI ARE ALONG
THE TRUNKS OF THE TREES AND ON THE BARK. THINGS LIKE THAT.

THEY'RE OCCUPYING DIFFERENT SPATIAL
PARTS OF THE HABITAT.

THEY'RE DIFFERENTIATING SPACE IN THIS CONCRETE WAY. THEY MAY

NOT
SHOW MUCH EVIDENCE FOR INTERACTION AT ALL. THEY MAY

OCCASIONALLY THROUGH THEIR DUE
LAP OUT AND DO PUSH-UPS AND MAKE

THEMSELVES VISIBLE, BUT PHYSICAL ENCOUNTERS MAY BE VERY
RARE.

SO ECOLOGISTS MIGHT SCRATCH HIS OR HER HEAD AND SAY WHERE'S THE

COMPETITION?
THEY'RE JUST OCCUPYING DIFFERENT SPACES. THEY'RE

DIVIDING THE COMMUNITY IN TERMS OF SPATIAL
RESOURCES. THEY'RE

ALL EATING SIMILAR THINGS. THEY'RE ALL EATING INSECTS THAT THEY



CAN FIT INTO THEIR MOUTH. BUT THEY'RE DOING IT IN DIFFERENT

PARTS OF THE HABITAT AND
THUS NOT INTERACTING. ECOLOGIST NUMBER

TWO MIGHT COME BY AND SAY, THIS SIGNALS THE FACT
THAT COMPETITION

OCCURRED IN EVOLUTIONARY TIME AND LEAD TO THE STRUCTURING OF THIS
GROUP OF SPECIES. IT SIGNALS THE GHOST OF COMPETITION PAST.

AND COMPETITION WAS A
REAL FORCE IN STRUCTURING THIS GROUP. WE

JUST DON'T SEE IT NOW BECAUSE IT HAS ACTED
AND ENSCONCED IN THESE

SPECIES, PARTICULAR NATURAL HISTORY TRAITS THAT THEY EXHIBIT
THEN CAUSES THEM TO DIFFERENTIATE, ENABLES THEM TO COEXIST IN THE

CONSISTENT WITH THE
COMPETITIVE EXCLUSION PRINCIPLE. ANOTHER MAYBE MORE CONCRETE SOURCE OF EVIDENCE

FOR COMPETITION
AND ITS INFLUENCE ON INDIVIDUAL MORPHOLOGY, THE

FORM OF ORGANISMS. MORPHOLOGY, JUST
REFERRING TO THE FORM OF A

CREATURE. THE WAY OF ITS APPEARANCE, THE WAY IT LOOKS. CHARACTER
DISPLACEMENT.

SOME GREAT EXAMPLES OF CHARACTER DISPLACEMENT, THERE ARE TOO MANY OUT THERE.
SOME GOOD ONES

FOR BIRDS AND SOME GOOD ONES FOR MAMMALS THAT I KNOW OF. HERE'S A NICE
ONE FROM

THE GROUP OF FINCHS, DARWIN FINCHES, GEOSPIZA FINCHES FROM THE GALAPAGOS ISLANDS.
ON THIS AXIS YOU HAVE THE DEPTH OF THE BEAK OF THE BIRD MEASURED LIKE

THIS. YOU CATCH
A BIRD IN ITS NET AND HOLD IT IN YOUR HANDS, YOU CAN

MEASURE THE BEAK. IT RANGES FROM
SOMETHING LIKE 7 TO

16 MILLIMETERS. THAT DEPTH OF BEAK IS KNOWN TO BE RELATED TO
THE THINGS THESE BIRDS EAT. THINGS WITH DEEPER BEAKS TEND TO HAVE GREATER

CAPACITY TO CRACK
HARD OBJECTS. AND THE EAT HEAVIER SEEDS. WHEN FULIGINOSA

AND FORTIS OCCUPY ISLANDS WITHOUT
THE OTHER SPECIES PRESENT, SO

WHEN THEY EXIST IN ALLOPATRY IN DISTINCT AREAS, ANOTHER
TERM FOR

LIVING IN DIFFERENT PLACES, THEY HAVE SIMILAR SIZED BEAKS WHEN





THEY'RE
LIVING ALONE WITHOUT THE PRESENCE OF THE OTHER. BUT ON

ISLANDS SUCH AS SANTA MARIA AND SAN
CRISTÓBAL WHERE THEY LIVE

TOGETHER, THEIR BEAK SIZES ARE QUITE DIFFERENT. THE AVERAGE,
THE MEAN SIZE OF THEIR BEAKS, IF YOU RAN A STATISTICAL TEST,

ALMOST CERTAIN TO BE DISTINCT
IN TERMS OF SIZE OF THE BEAKS. IN

THESE TWO POPULATIONS WHEN LIVING SYMPATRICLY TOGETHER.
ASSUMPTION BEING WHEN THE LIVE TOGETHER, THEY NEED TO

DIFFERENTIATE THEIR USE OF RESOURCES.
AND IN DOING SO NATURAL

SELECTION HAS LEAD TO DIFFERENTIATION AND MORPHOLOGY, IN BEAK
MORPHOLOGY IN THE FORM OF

THEIR BILLS RELATED TO THEIR DIFFERENT DIETS. I HAVE INTRODUCED
A FEW

TERMS HERE WHICH YOU'LL USE AGAIN AND AGAIN IN THE

EVOLUTION SECTION. A FAMOUS
OLD PICTURE. I DON'T KNOW WHERE THIS PICTURE CAME FROM,

BUT I SEE IT AROUND FAIRLY OFTEN.
GREAT IMAGE TO ILLUSTRATE A FEW THINGS. I JUST LIKE THE AFRICAN

SAVANNAH. MAYBE NOT
A GREAT IMAGE FOR ALL OF YOU. BUT THIS IS A FASCINATING

LOCATION ON THE PLANET. THIS
TYPE OF SETTING ON THE AFRICAN

PLAIN, OPEN COUNTRY. YOU'LL SEE MY WIFE. I'M SO INTERESTED
IN THAT KIND OF SETTING MORE AND MORE AS I GO ON TO TALKING MORE

AND MORE ABOUT HUMAN
EVOLUTION. HUMANS EVOLVED IN THIS

PART OF THE WORLD AND WE HAVE A LONG HISTORY WITH
THESE KINDS OF

DYNAMICS. IT'S NOT A SITE YOU WANT TO BE HANGINGING AROUND AT A KILL
LIKE THIS

BECAUSE IT'S VERY DYNAMIC AND AGGRESSIVE. WHAT'S HAPPENING

HERE? WHAT
DO THESE ARROWS REPRESENT? BETWEEN THE HYENA AND THE

VULTURE, WHAT HAVE WE? WE HAVE INTERFERENCE
COMPETITION POTENTIALLY. IF THE

HYENA WANTS TO RUN THE VULTURE OFF, TO KILL. OR IF THE
VULTURES

BECOME SO NUMEROUS, THEY CAUSE THE HYENAS PROBLEMS. THAT'S

USUALLY MORE
ONE SIDE WITH THE HYENA RUNNING OFF THE VULTURE. THE




HYENA AND THE ZEBRA, THAT ARROW
COULD ALSO RUN FROM THE VULTURE TO THE ZEBRA, WOULD REPRESENT CONSUMPTION, FOOD

CONSUMPTION
AND PREDATION, RIGHT? BUT WHAT IF THE LIONS ARE ON

THE HORIZON? WHO'S GOING TO SEE THEM
FIRST? PROBABLY A COUPLE

OF THE CIRCLING VULTURES. AND WORD IS GOING TO GET DOWN TO
THE

OTHER VULTURES AND THEN THE HYENAS ARE GOING TO BECOME AWARE.

YOU MIGHT ALSO THINK
OF THAT ARROW BETWEEN THE VULTURE AND THE

HYENA AS SOMETHING COOPERATIVE. WHERE THEY'RE
BOTH CONCERNED

ABOUT LIONS AND THE VULTURE MIGHT BE THE ONE TO SEE THEM FIRST,

OR MAYBE
IT'S THE HYENA BY CHANCE. AND THEY TELL THE OTHER.

SO IT'S A COOPERATIVE ARRANGEMENT
BETWEEN THEM AS WELL. ONE

THING THIS HIGHLIGHTS AS THE DYNAMISM OF THE RELATIONSHIPS,

WHERE
THE RELATIONSHIP CAN BE INTERFERENCE COMPETITION OR

EXPLOITATIVE COMPETITION, IT CAN TURN
INTO COOPERATION. IT CAN

TURN INTO OTHER FORMS IN TIME. AND IT DOES. SO MOVING INTO
SOME OF THESE OTHER TYPES AND THIS IS WHERE I'LL MOVE SOMEWHAT BRISKLY TO GE THROUGH A
LOT OF PICTURES,

STILL ALL VERY IMPORTANT. BUT I WANT TO TRY TO GET THROUGH THIS

MATERIAL.
THE TRUE PREDATORS HAVE MANY HOSTS, USING THAT TERM,

THE TERM HOST IN A FAMILIAR WAY.
AND THE RELATIONSHIP IS LETHAL

IN THE SENSE THAT THE PREDATOR KILLS THE PREY, THE HOST.
AND HAS TO DO SO

AGAIN AND AGAIN TO SUSTAIN ITSELF. AND JUST AN EXAMPLE THERE,

ONE OF
OUR WORLD'S GREAT PREDATORS, THE PRAYING MANTIS, WHICH YOU CAN FIND AROUND BERKELEY. I FOUND
ONE ON TELEGRAPH LAST YEAR. IN A DOORWAY ON TELEGRAPH AVENUE,
RIGHT THERE DOWNTOWN. GREAT CREATURES. YOU CAN HANDLE THEM,

THEY WON'T HURT YOU. ABSOLUTELY
FASCINATING. THEY WILL LOOK

YOU IN THE EYE AND YOU'LL HAVE THIS UNCANNY EXPERIENCE OF
THEIR

STARING YOU IN THE EYE. BUT THE PREY OF PREDATORS GO TO GREAT





LENGTHS TO
AVOID BEING CONSUMED BECAUSE IT'S A LETHAL

ARRANGEMENT. IT DOESN'T SERVE THEM VERY WELL
IN THEIR FITNESS TO DIE. SO A LOT OF

TIMES YOU'LL SEE MORPHOLOGICAL ADAPTATIONS TO AVOID
PREDATION WHERE THEY'RE JUST BEING SPINY AND DIFFICULT TO EAT.

ALL THESE CASES, PORCUPINES
AND FISHERS, ONE OF THE ONLY CONSISTENT
PREDATORS OF PORCUPINES IN NORTH AMERICA, THE FISHER. USUALLY YOU HAVE SOME TYPE OF
PREDATOR THAT CAN OVERCOME THOSE DEFENSES, BUT ATTEMPT TO DEFEND

THEMSELVES IN VARIOUS
WAYS A HOST WILL. APOSEMATISM IS JUST A REFERENCE TO

WARNING COLORATION THAT SIGNALS TO A
PREDATOR THAT I SHOULD NOT

BE EATEN FOR SOME REASON. IN THE CASE OF THESE POISON DART
FROGS IT'S

BECAUSE OF THE TOXINS IN THEIR SKIN. THEY'RE EXTREMELY TOXIC.

AND TO EAT
THEM IS A LEGITIMATE RISK TO THE CONSUMER. AND IT CAN

KILL THE CONSUMER. THEY ADVERTISE
THEMSELVES. THEY LOOK VERY STRIKING

AND THEY STAND OUT. THEY ADVERTISE THEMSELVES.
THAT'S WHAT WE

MEAN IN THIS CONTEXT OF APOSEMATISM. OFTEN ORANGE AND BLACKS OR YELLOWS AND

BLACKS.
IF YOU TURN THE CORNER, YOU WILL SEE THIS, AND YOU'LL

JUMP. YOU JUMP, WELL, MAYBE NOT
IF THEY'RE LITTLE BABIES AND THEY'RE THAT CUTE.
IF THEY'RE GROWN UP AND BIGGER AND YOU SEE

BLACK AND WHITE WHEN YOU TURN THE CORNER IT'LL
GIVE YOU A STARTLE. IT'S

ALMOST INSTINCTUAL REACTION TO THAT TYPE OF WARNING COLORATION,
BLACK ON WHITE. BUT ALSO THINGS LIKE CRYPTICITY AND CAMOUFLAGE,

BLENDING INTO THE SURROUNDINGS,
THAT'S OFTEN A DEFENSE AGAINST

PREDATORS. INSTEAD OF ADVERTISING YOURSELF, YOU TRY TO
BE

OVERLOOKED. THERE'S A FROG IN THERE. PROBABLY AGAINST A BUNCH OF LICHEN.

A DISTINGUISHED
CRYPTICITY FROM CAMOUFLAGE, MAYBE. BECAUSE CRYPTICITY CAN BE IN BEHAVIOR.
IF YOU WATCH A CHAMELEON WALK

ALONG A BRANCH OR A STICK INSECT, THEY'LL OFTEN SHIFT BACK
AND

FORTH, SHIFT BACK AND FORTH AS IF THEY'RE BLOWING IN THE WIND.

THEY'LL MAKE THEMSELVES
LOOK CRYPTIC AS THEY MOVE. CAMOUFLAGE YOU CAN THINK OF IN TERMS





OF COLOR MATCHING
TO THE BACKGROUND.

I'LL GIVE YOU THE SLIDE AND YOU CAN LOOK FOR THE CREATURES THAT MIGHT
BE PRESENT.
SOMETHING ELSE YOU'LL GET IN THE EVOLUTION SECTION, SO I'LL

GLOSS OVER HERE, I THINK
IS FROM THIS PART OF THE BOOK.

MIMICRY. AGAIN, YOUR BLACK AND YELLOW COLORATION SIGNALS
A THREAT. AND IN

THE CASE OF YELLOW JACKETS AND WASPS AND THINGS, BLACK AND

YELLOW USUALLY
SIGNALS THE FACT THAT IT CAN STING YOU. OTHER

ORGANISMS COEXISTING WITH ORGANISMS WITH WARNING
COLORATION MAY

COME TO RESEMBLE THEM. I'LL LET THIS BE DEALT WITH IN

EVOLUTION PRIMARILY.
BUT KNOW THAT THIS TYPE OF MIMICRY CAN BE HONEST OR

DISHONEST. THE MIMICKING ORGANISM
MIGHT ALSO HAVE THE DEFENSES THAT THE

MIMICKED HAS. OR IT MIGHT BE BLUFFING. AND WE DISTINGUISH
MÜLLERIAN FROM BATESIAN MIMICRY TO DISTINGUISH HONEST FROM DISHONEST TYPES OF

MIMICRY.
HERE YOU HAVE A LARVA, LIKE A CATERPILLAR LOOKING AN

AWFUL LOT LIKE A SNAKE. IF A
BIRD IS GOING TO COME IN AND TRY

TO EAT THIS, AND IT FLARES UP, AND LOOKS LIKE A SNAKE,
MAYBE THAT

MIGHT BE A SUFFICIENT STARTLE TO THE BIRD TO FLY AWAY AND LEAVE IT ALONE.
IT'S

BLUFFING, TRYING TO LOOK DANGEROUS WHEN, IN FACT, IT'S RATHER

QUITE HARMLESS.
SO WE DISTINGUISH THESE TWO TYPES OF MIMICRY.

LOOK AT THE PREDATOR-PREY CYCLES AND A COUPLE
OF CLASSIC EXAMPLES. FROM

LAKE SUPERIOR ON ISLE ROYALE. LAKE SUPERIOR FROZE OVER HARD
EARLY IN THE 1900S. AND MOOSE

WALKED ACROSS THE FROZEN ICE AND CAME TO OCCUPY THAT ISLAND
FOR

THE FIRST TIME. IT TURNED OUT TO BE A BOUNTIFUL ISLAND AND

POPULATION NUMBERS
INCREASED QUITE A LOT. THERE WAS A LOT TO

EAT. MOOSE LIKED TO WADE IN THE WATER AND
EAT THE AQUATIC

VEGETATION AND THEY WERE QUITE HAPPY THERE. UNTIL THE LAKE FROZE AGAIN
AND





THE WOLVES ARRIVED. AND THEY CROSSED THE ICE AND JOINED THE

MOOSE ON ISLE ROYALE,
AND SETTING UP A FASCINATING STUDY FOR ECOLOGISTS TO STUDY

PREDATOR-PREY DYNAMICS BECAUSE
WOLF HUNT IN PACKS AND EAT MOOSE. AND THERE'S A LOT OF FOOD THERE.

AND ONE MOOSE KILL
CAN SUSTAIN A FEW WOLVES FOR A LITTLE WHILE.

WHAT ECOLOGISTS WERE PREPARED TO DO IN THIS
INSTANT WAS TO MONITOR THE POPULATION NUMBERS

OF BOTH WOLVES AND MOOSE. AND TO LOOK AT THE
CORRELATIONS BETWEEN

THEM IN TIME. I'LL LET YOU EXPLORE THIS IN YOUR BOOK AS WELL.
BUT NOTE THAT THESE PREDATOR-PREY CYCLES OFTEN APPEAR TO BE ENTRAINED IN SOME WAY. THEY'RE
CORRELATED. AND WHAT BECOMES DIFFICULT TO SORT OUT IS CAUSAL

RELATIONSHIPS BETWEEN
POPULATIONS. THEY'RE VERY OFTEN CLEARLY

CORRELATED BUT CAN YOU ASSUME THAT THE CORRELATION
IS ALSO CAUSAL

WHERE THE CHANGES IN THE NUMBERS OF ONE POPULATION ARE CAUSING THE
CHANGE IN THE NUMBERS OF THE OTHER. IN THIS CASE, WHEN MOOSE WERE

SEEN TO INCREASE HERE,
THE WOLVES WERE SEEN TO UNDERGO A PARALLEL

BUT JUST SLIGHTLY STAGGERED IN TIME INCREASE
ALSO TO A HIGH POINT

OF MANY, MANY WOLVES ON THE ONE ISLAND AROUND 1980. THIS CAUSED
APPARENTLY, THIS WAS CORRELATED WITH DECLINE IN MOOSE. AND A

CRASH IN WOLVES. AND YOU
CAN FOLLOW THE CYCLES. AND READ

ABOUT IT AND THINK ABOUT CORRELATION AND CAUSATION.
ANOTHER

FAMOUS EXAMPLE, SORRY ABOUT THE MAMMALS EATING OTHER MAMMALS BUT THESE ARE
THE THINGS I LIKE A LOT.

HERE YOU HAVE A VERY LARGE CAT, CALLED A LYNX AND A FAIRLY
BIG

RABBIT CALLED A SNOWSHOE HARE. AND THE LYNX DEPENDS QUITE A LOT ON THESE BIG

HARES.
THESE ARE THE HARES THAT CHANGE THEIR PELAGE OVER THE COURSE OF THE SEASON SO
THEY'LL BE MORE CAMOUFLAGED IN SUMMER AND ALSO IN WINTER.

BUT THAT DOESN'T KEEP THEM,
OF COURSE, FROM BEING CONSUMED BY THE

LYNX. OH, NO. IT GOT AWAY, I PROMIS. [LAUGHTER]
AT THE ECOLOGICAL LEVEL HERE, THESE NUMBERS WERE





TRACKED ALL THE WAY BACK IN TIME
AS A RESULT OF THE VERY CAREFUL

ACCOUNTING THAT HUNTERS DID IN IDENTIFYING THE NUMBER
OF PELTS THAT THEY

OBTAINED THROUGH THE TRAPPING AND HUNTING SEASONS. THEY HAD TO
REPORT THESE NUMBERS FOR THE LOCAL AUTHORITIES AND APPARENTLY

THEY DID SO WITH SOME FAITHFULNESS.
SO ECOLOGISTS COULD GO BACK

AND MINE THOSE OLD RECORDS TO LOOK AT THE NUMBERS OF INDIVIDUALS
OF THESE POPULATIONS OVER TIME. AND THERE APPEAR TO BE THIS FANTASTIC

ENTRAINMENT
OF NUMBERS OF THE TWO POPULATIONS IN TIME. YET THE

CORRELATION EXISTS BUT THE CAUSAL
RELATIONSHIPS ARE VERY SUBTLE.

AND SOME PEOPLE EVEN SPECULATE THAT THEY'RE RELATED
MORE TO SOLAR

ACTIVITY THAN DIRECTLY TO DYNAMICS ON THE GROUND. AS A RESULT OF

CHANGES
IN SOLAR ACTIVITY YOU COULD HAVE CHANGES IN VEGETATION THAT

PROPAGATE THROUGH THE HERBIVORE
AND THAT INFLUENCE THE PREDATOR.

I GOT YOU FOR TWO MORE MINUTES, GUYS. SETTLE DOWN
FOR A LITTLE BIT LONGER.

SO, YEAH, YOU CAN READ FURTHER ABOUT THAT IN YOUR BOOK.
HERBIVORY CAN BE CONSIDERED IN TERMS OF ITS EFFECTS AS A VERY

SIMILAR PREDATION. BECAUSE
IT BENEFITS ONE PARTICIPANT AND

HARMS THE OTHER. AND HERBIVORY CAN BE ANYTHING FROM
GRAZING BUFFALO OR DUGONGS

AND MANATEES UNDER WATER OR CATERPILLARS AND LEAVES. IT'S
THE

CONSUMPTION OF PLANTS OR ALGAE BY A CONSUMING ORGANISM. YOU'LL

GET A LOT MORE
INTO THIS IN THE BOTANY SECTION. AND PLANTS HAVE

FANTASTIC DEFENSES AGAINST BEING EATN.
YOU'LL HEAR MUCH MORE ABOUT THAT. JUST

NOTE FOR MY PURPOSES SOME OF THE DIVERSITY OF TYPES
OF HERBIVORY.
NECTAR CONSUMPTION OR THE EATING OF FRUIT BY FRUIT BATS

THE USE OF GUNS AND SAPS ARE
ALL TYPES OF PLANT CONSUMPTION OR

HERBIVORY. MUTUALISMS WE CAN SAVE AND TALK ABOUT NEXT
TIME.

THANKS EVERYBODY.