POPULATION DYNAMICS

POPULATION DYNAMICS

• POPULATION– POPULATION DEF??– POPULATION ECOLOGY• CONCERNED WITH THE CHANGES IN POPULATION SIZE

AND THE FACTORS THAT REGULATE POPULATIONS OVER TIME

POPULATION DYNAMICS

• POPULATION ECOLOGY

POPULATION DYNAMICS

• DENSITY AND DISPERSION PATTERNS ARE IMPORTANT POPULATION VARIABLES– POPULATION DENSITY

• THE NUMBER OF INDIVIDUALS OF A SPECIES PER UNIT AREA OR VOLUME

• IT’S EXTREMELY DIFFICULT TO COUNT ALL THE INDIVIDUALS IN ANY POPULATION, SO SCIENTISTS USE VARIOUS SAMPLING TECHNIQUES– TAG & RECAPTURE METHOD

POPULATION DYNAMICS

• DENSITY AND DISPERSION PATTERNS ARE IMPORTANT POPULATION VARIABLES– DISPERSION PATTERN• REFERS TO THE WAY INDIVIDUALS

ARE SPACED WITHIN THEIR AREA• 3 MAJOR PATTERNS

– CLUMPED– UNIFORM– RANDOM

POPULATION DYNAMICS

POPULATION DYNAMICS

POPULATION DYNAMICS

• IDEALIZED MODELS HELP US UNDERSTAND POPULATION GROWTH– EXPONENTIAL

GROWTH MODEL• RATE OF

EXPANSION OF A POPULATION UNDER IDEAL CONDITIONS; UNREGULATED GROWTH

POPULATION DYNAMICS

• IDEALIZED MODELS HELP US UNDERSTAND POPULATION GROWTH– POPULATION

-LIMITING FACTORS AND THE LOGISTIC GROWTH MODEL

POPULATION DYNAMICS

• IDEALIZED MODELS HELP US UNDERSTAND POPULATION GROWTH– IDEALIZED MODELS DON’T EXIST IN NATURE!!– POPULATION-LIMITING FACTORS• ENVIRONMENTAL FACTORS THAT RESTRICT

POPULATION GROWTH

– LOGISTIC GROWTH MODEL• IDEALIZED POPULATION GROWTH THAT IS SLOWED BY

LIMITING FACTORS AS THE POPULATION SIZE INCREASES

POPULATION DYNAMICS

• LOGISTIC GROWTH MODEL– CARRYING

CAPACITY • THE

MAXIMUMPOPULATIONSIZE THAT ANENVIRONMENTCAN SUPPORTAT APARTICULARTIME, WITHNODEGRADATIONTO THEHABITAT

POPULATION DYNAMICS

• MULTIPLE FACTORS MAY ACT AS LIMITING AGENTS– COMPETITION FOR LIMITED RESOURCES

• FOOD, TERRITORY, MATES, ETC.

– INCREASED DISEASE TRANSMISSION– PHYSIOLOGICAL FACTORS ARE IMPACTED BY DENSE

POPULATIONS– ABIOTIC FACTORS MAY IMPACT POPULATION SIZE

• *SOME POPULATIONS HAVE “BOOM-AND-BUST” CYCLES*– THIS IS NOT FULLY UNDERSTOOD

POPULATION DYNAMICS

• WHAT DOES THE LOGISTIC GROWTH MODEL REALLY LOOK LIKE IN A STABLE ENVIRONMENT??

POPULATION DYNAMICS

• HUMAN POPULATION GROWTH

POPULATION DYNAMICS

• LIFE TABLES TRACK MORTALITY AND SURVIVORSHIP IN POPULATIONS– SURVIVORSHIP CURVES• PLOT THE

PROPORTION OFINDIVIDUALS ALIVE AT EACH AGE

POPULATION DYNAMICS

• BIRTH AND DEATH RATES AND AGE STRUCTURE AFFECT POPULATION GROWTH– ZERO POPULATION GROWTH (ZPG) IS WHEN

BIRTH RATES EQUAL DEATH RATES

POPULATION DYNAMICS

• BIRTH AND DEATH RATES AND AGE STRUCTURE AFFECT POPULATION GROWTH– AGE STRUCTURE• THE PROPORTION OF INDIVIDUALS IN DIFFERENT AGE-

GROUPS

POPULATION DYNAMICS

• TWO IMPORTANT PRACTICAL USES OF POPULATION DYNAMICS INCLUDE– RENEWABLE RESOURCE MANAGEMENT• HARVESTING CROPS WITHOUT DAMAGING THE

RESOURCE

– MAXIMUM SUSTAINABLE YIELD• HARVESTING AT A LEVEL THAT PRODUCES A

CONSISTENT YIELD WITHOUT DAMAGING THE POPULATION

POPULATION DYNAMICS

• THAT’S POPULATION ECOLOGY…BUT HOW DO ALL OF THE DIFFERENT POPULATIONS GET ALONG??

• THAT’S COMMUNITY-LEVEL ECOLOGY, AND THAT’S NEXT!!!