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