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Population Dynamics: Factors Affecting Density and Population Growth in Ecology - Prof. Ro, Study notes of Biology

Central Michigan University (CMU)Biology
Prof. Robert Bailey

An overview of population dynamics, focusing on the factors affecting density and population growth in ecology. Topics include natality, mortality, immigration, emigration, density measurements, population growth rates, and exponential growth. The document also discusses the assumptions and limitations of population models.

Typology: Study notes

Pre 2010

Uploaded on 08/30/2009

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•POPULATION SIZE
•REGULATION OF POPULATIONS
•POPULATION GROWTH RATES
•SPECIES INTERACTIONS
•
•DENSITY
DENSITY = NUMBER OF
INDIVIDUALS PER UNIT AREA
OR VOLUME
•
•POPULATION GROWTH
POPULATION GROWTH =
CHANGE IN DENSITY OVER
TIME
FOUR (4) FACTORS
AFFECTING DENSITY
NATALITY (+)
NATALITY (+) MORTALITY (-)
MORTALITY (-)
IMMIGRATION (+)
IMMIGRATION (+)
EMIGRATION
EMIGRATION
FOUR (4) FACTORS
AFFECTING DENSITY
•
•IMMIGRATION
IMMIGRATION
•
•EMIGRATION
EMIGRATION
–ASSUME THESE TWO ARE
EQUAL
DENSITY FUNCTIONS
(CONT’D)
•NATALITY: PROCESS OF ADDING NEW
INDIVIDUALS TO POPUL. VIA BIRTHS
–FERTILITY = PERFORMANCE
(ACTUAL?) BASED ON NUMBERS
BORN (HUMANS)
–FECUNDITY = POTENTIAL LEVEL OF
PERFORMANCE BASED UPON MEAN
GESTATION TIME (HUMAN POPUL.)
DENSITY FACTORS
(CONT’D)
•MORTALITY: DECREASE IN NUMBER
OF INDIVIDUALS BY DEATH RATE
–PHYSIOLOGICAL LONGEVITY = MEAN
LIFE SPAN UNDER OPTIMUM CONDITIONS
•SENESCENCE DEATH = OLD AGE
–ECOLOGICAL LONGEVITY = EMPERICAL
MEAN LIFE SPAN UNDER ANY GIVEN
CONDITIONS
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Download Population Dynamics: Factors Affecting Density and Population Growth in Ecology - Prof. Ro and more Study notes Biology in PDF only on Docsity!

  • POPULATION SIZE
  • REGULATION OF POPULATIONS
  • POPULATION GROWTH RATES
  • SPECIES INTERACTIONS
    • • DENSITYDENSITY = NUMBER OF

INDIVIDUALS PER UNIT AREA

OR VOLUME

  • • POPULATION GROWTHPOPULATION GROWTH =

CHANGE IN DENSITY OVER

TIME

FOUR (4) FACTORS

AFFECTING DENSITY

NATALITY (+)NATALITY (+) (^) MORTALITY (-)MORTALITY (-)

IMMIGRATION (+)IMMIGRATION (+)

EMIGRATIONEMIGRATION

FOUR (4) FACTORS

AFFECTING DENSITY

  • • IMMIGRATIONIMMIGRATION
  • • EMIGRATIONEMIGRATION

–ASSUME THESE TWO ARE

EQUAL

DENSITY FUNCTIONS

(CONT’D)

  • NATALITY: PROCESS OF ADDING NEW

INDIVIDUALS TO POPUL. VIA BIRTHS

  • FERTILITY = PERFORMANCE

(ACTUAL?) BASED ON NUMBERS

BORN (HUMANS)

  • FECUNDITY = POTENTIAL LEVEL OF

PERFORMANCE BASED UPON MEAN

GESTATION TIME (HUMAN POPUL.)

DENSITY FACTORS

(CONT’D)

  • MORTALITY: DECREASE IN NUMBER

OF INDIVIDUALS BY DEATH RATE

– PHYSIOLOGICAL LONGEVITY = MEAN
LIFE SPAN UNDER OPTIMUM CONDITIONS
  • SENESCENCE DEATH = OLD AGE
  • ECOLOGICAL LONGEVITY = EMPERICAL MEAN LIFE SPAN UNDER ANY GIVEN CONDITIONS

DENSITY MEASUREMENTS

  • ABSOLUTE DENSITY: TOTAL COUNTS (DIFFICULT/SOME ERROR) - HUMAN POPULATION CENSUS - BIRDS: ALL SINGING MALES INAREA - LARGE PLANTS IN GIVEN AREA

(TREES)

DENSITY MEASUREMENTS

(CONT’D)

  • DENSITY ESTIMATES
    • USE OF QUADRATS (PLANTS, SMALL ANIMALS)
    • CAPTURE-RECAPTURE (MOBILE POPUL)
      • CLOSED: NOT CHANGE SIZE DURING SAMPLE PERIOD
      • OPEN: CHANGES IN SIZE DURING SAMPLE PERIOD
      • NOTE: REAL POPULATIONS ARE OPEN

DENSITY ESTIMATES

(CONT’D)

  • PETERSON INDEX: PROPORTIONAL

COMPUTATION OF MARKED VS.

UNMARKED INDIVIDUALS IN SAMPLE

MARKED IND. = MARKED IN TOT. POPUL.
TOTAL CAUGHT = TOTAL POPUL. SIZE

POPULATION GROWTH

  • RATE OF GROWTH: CHANGE IN

NUMBERS PER UNIT TIME

  • EXPONENTIAL GROWTH

(UNRESTRICTED ENVIRONMENT)

– FUNCTION OF TWO (2) FACTORS
  • SIZE OF POPULATION AT TIME ZERO
  • CAPACITY OF POPULATION TO INCREASE (I.E., BIOTIC POTENTIAL) OR DECREASE IN SIZE OVER TIME

r = b - d

INNATE CAPACITY FOR

NATURAL INCREASE

• NET REPRODUCTION PER INDIVIDUAL PER

UNIT OF TIME ( r ) =

(BIRTH RATE PER INDIVIDUAL PER UNIT OF TIME) - (DEATH RATE PER INDIVIDUAL PER UNIT OF TIME)

CHARACTERIZES J-SHAPED CURVE EXPONENTIAL GROWTH

N (^) t +1 = r * N (^) t

EXPONENTIAL GROWTH

TIME

NUMBERS

J-SHAPED GROWTH CURVE

EXPONENTIAL GROWTH

• Nt = N 0 ert

dN/dt = r * N

dN

t+

/dt = r * N

t

  • NOTE: DEPENDENT & INDEPENDENT

VARIABLES IN CURVE

  • CHANGE THROUGH TIME
  • r IS CONSTANT FOR ANY PARTICULAR

POINT IN TIME FOR GIVEN

ENVIRONMENTAL CONDITIONS

  • IND > RAPIDLY; RATE OF CHANGE

REMAINS CONSTANT

dN/dt = r * N

  • r = BIOTIC POTENTIAL OR INTRINSIC RATE OF NATURAL INCREASE
  • POPULATION GROWTH RATE DEFINED PER INDIVIDUAL (FEMALE) - ASSUME UNCROWDED CONDITIONS - STABLE AGE CLASS DISTRIBUTION - POTENTIAL GROWTH VS. ACTUAL
  • r IS AN INNATE QUALITY OF A SPECIES JUST AS MEAN WT., SIZE, ETC
• SIMILAR TO MEAN LONGEVITY, NATALITY,
GROWTH RATE
• FUNCTION OF:
• ENVIRONMENTAL CONDITIONS
• INTRINSIC NATURE OF SPECIES IN
QUESTION
• DIFFICULT TO MEASURE DUE TO DUE TO
CHANGING ENVIRONMENTAL CONDITIONS
• ATTEMPTS TO STANDARDIZE (OPTIMIZE)

INNATE CAPCITY FOR

NATURAL INCREASE dN/dt = r * N

• SHOULD BE CLEAR FROM EQUATION:
  • IF r = 1: NO CHANGE (GROWTH) IN POPULATION SIZE
  • IF r < 1--DECREASE IN SIZE
  • IF r > 1--INCREASE IN SIZE

• ORDER OF MAGNITUDE OF r DETERMINES

RATE OF CHANGE

• IF r REMAINS CONSTANT, THEN RATE OF

CHANGE IS CONSTANT

ASSUMPTIONS

  • UNREALISTIC--BUT GOOD BEGINNING POINT FOR CONSIDERATION OF POPULATION MODELS
  • BIOTIC POTENTIAL DOES NOT REMAIN CONSTANT IN NATURE
  • ATTEMPTS TO MEASURE IN NATURE NOT SIMPLE
  • r VARIES WITH ENVIRONMENTAL CONDITIONS, AGE DIST., GENETIC COMPOSITION, SOCIAL STRUCTURE, ETC..

S-SHAPED GROWTH CURVE LOGISTIC GROWTH

=K

dN/dt = r*N(K-N/K)

K = MAXIMUM NUMBER OF INDIVIDUALS THAT CAN BE SUPPORTED BY THE ENVIRONMENT AT THAT TIME

dN/dt = r*N

LOGISTIC GROWTH:

dN/dt = rN(K-N/K)*

  • K = CARRYING CAPACITY
    • MAXIMUM NUMBER OF INDIVIDUALS THAT CAN BE SUPPORTED (INDEFINITELY--ASSUMING EVERYTHING REMAINS THE SAME) INA GIVEN AREA (ENVIRONMENT)

LOGISTIC GROWTH:

dN/dt = rN(K-N/K)*

  • (K-N/K) IS A MEASURE OF ENVIRONMENTAL RESISTANCE - DIRECT EFFECT OF CROWDING
  • REPRESENTS AN INVERSE MEASURE OF ENVIRONMENTAL RESISTANCE - WHEN ENVIR. RESIST. IS LOW, VALUE OF (K-N/K) APPROACHES VALUE OF 1
  • VARIOUS FACTORS AFFECT K
    • ANYTHING WHICH AFFECTS BIRTH RATE OR DEATH RATE WILL IMPACT K

REGULATION OF POPULATION SIZE & RATE OF CHANGE

  • DENSITY DEPENDENT FACTORS
    • CROWDING EFFECT
  • DENSITY INDEPENDENT FACTORS
    • OTHER ENVIRONMENTAL

RESISTANCE FACTORS

  • CARRYING CAPACITY EFFECTS
    • LOGISTIC GROWTH

SPECIES INTERACTIONS

  • SPACING (PATTERNS OF

DISTRIBUTION)

  • PREDATOR-PREY INTERACTIONS
  • INTERSPECIFIC COMPETITION
  • EFFECTIVENESS OF COMPETITION
  • LOTKA-VOLTERRA MODELS

TWO SPECIES

INTERACTIONS

  • PREDATOR-PREY INTERACTIONS
    • TIME LAGS
  • COMPETITIVE INTERACTIONS
  • INTRERSPECIFIC COMPETITION
  • OCCURS WITH SYMPATRIC

DISTRIBUTION OF TWO/MORE SPECIES

IN SAME AREA

PREDATOR-PREY

INTERACTIONS

  • TIME LAG EFFECTS
  • ARRAY OF FACTORS AFFECTING

EACH SPECIES IN QUESTION INDEPENDENT OF DIRECT INTERSPECIFIC COMPETITION

INTERSPECIFIC

COMPETITION

  • WILL OCCUR WITH SYMPATRIC

DISTRIBUTION OF TWO OR MORE

SPECIES

  • DEGREE OF INTERACTION

(SEPARATION) MAY BE DEFINED WITH

RESPECT TO SPECIFIC RESOURCES

– FOOD SIZE PREFERENCE

EFFECTIVENESS OF COMPETTION

  • ABILITY OF ONE SPECIES TO UTILIZE AVAILABLE RESOURCES THAN THE OTHER - KEY LIMITING RESOURCES, OR MANY OTHERS
  • FUNCTION OF ENVIRONMENTAL CONDITIONS
  • GENETIC/SOCIAL STRUCTURE FACTORS
  • SUPPORTED BY LAB STUDIES
  • TEMP VARIATION, HUMIDITY, FOOD QUAL & QUANTITY, ACCUM. WASTE PRODUCTS

COMPETITIVE EXCLUSION

  • GAUSE:
  • NO TWO (2) SPECIES CAN EXIST (SURVIVE) ON SAME LIMITING RESOURCES…AT SAME TIME ALL OF THE TIME
  • SPECIES WITH IDENTICAL RESOURCE REQUIREMENTS CANNOT CO-EXIST
  • CONCEPT OF NICHE, NICHE OVERLAP

COMPETITIVE EXCLUSION

PRINCIPLE (GAUSE)

  • NO TWO (2) SPECIES CAN EXIST (SURVIVE) ON THE SAME LIMITING RSOURCE...AT THE SAME TIME, ALL OF THE TIME
  • SPECIES WITH IDENTICAL RESOURCE REQUIREMENTS CANNOT CO-EXIST - LEADS TO CONCEPT OF NICHE, NICHE OVERLAP, ETC. (LATER DISCUSSIONS)
  • CONCEPT OF NICHE, NICHE OVERLAP