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POPULATION ECOLOGY
POPULATION ECOLOGY
Population: all the individuals of a species that live together in an area
Demography: the statistical study of populations, make predictions about how a population will change
Population Dynamics
Three Key Features of Populations
•Size
•Density
•Dispersion
(clumped, even/uniform, random)
Three Key Features of Populations
1. Size: number of individuals in an area
Growth Rate = Birth Rate - Death Rate
(# individuals born - # individuals die)
Age Distribution
Number of individuals in different age groups of a population
Indicates the potential of a population to increase, decrease or remain stable in size over time
RATE OF GROWTH & AGE DISTRIBUTION
PRE-REPRODUCTIVE
REPRODUCTIVE
POST-REPRODUCTIVE
Population of a Stable Country
THREE TYPES OF POPULATIONS
Which is growing faster? You decide!
Three Key Features of Populations
2. Density: measurement of population per unit area or unit volume
Pop. Density = # of individuals ÷ unit of space
1. Immigration- movement of individuals into a population
2. Emigration- movement of individuals out of a population
4 Factors that affect density
4 Factors that affect density
3. Density-dependent factors- Biotic factors in the environment that have a greater limiting effect as population size increases
Examples: disease
competition
parasites
4. Density-independent factors- Abiotic factors in the environment that affect populations regardless of their density
Examples: temperature storms
habitat destruction drought
4 Factors that affect density
Immigration
Emigration
Births DeathsPopulation
Change
++
-
-
Factors That Affect Future Population Growth
Three Key Features of Populations
3. Dispersion: describes the spacing or organisms relative to each other
• clumped
• even or uniform
• random
clumped
even (uniform)
random
THREE TYPES OF DISPERSION
Population Dispersion
OTHER FACTORS THAT AFFECT POPULATION GROWTH
Limiting factor - any biotic or abiotic factor that restricts the existence of organisms in a specific environment Examples: Amount of water
Amount of foodCompetitionPredationAmount of living spaceDiseaseParasitism
Can be density dependent or independent
Carrying Capacity- the maximum population size that can be supported by the available space and environmental resources
Carrying capacity can change as limiting factors become more or less severe for a given population
OTHER FACTORS THAT AFFECT POPULATION GROWTH
TWO BASIC PATTERNS OF POPULATION GROWTH
Carrying Capacity (k)
Nu
m
b
e
r
Time
J-shaped curve (exponential growth)
S-shaped curve (logistic growth)
CARRYING CAPACITY
-------------------------------------------------- CARRYING CARRYING
CAPACITYCAPACITY
2 Life History Patterns
1. R Strategists short life span small body size reproduce quickly have many young little parental care Examples:
cockroaches, weeds, bacteria
2 Life History Patterns
2. K Strategists long life span large body size reproduce slowly have few young provides parental
care Examples: humans,
elephants
HUMAN POPULATION THROUGH THE AGES
HUMAN POPULATION THROUGH THE AGES
Human Population Growth