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!!!