How Populations Grow Ecology

POINT > Identify ways we describe populations POINT > Describe ways that populations change POINT > Examine population growth patterns POINT > Define carrying capacity POINT > Identify density-dependent and density-independent population factors

POINT > Identify ways we describe populations 1. Geographic Range: Area inhabited by a population Habitat of Canis lupis (Gray wolf) shown in red

POINT > Identify ways we describe populations 2. Density & Distribution Density: Distribution: Number of individuals per unit area Higher Lower How individuals are spaced out Random Uniform Clumped

a) is the same as population distribution WB CHECK: Population density a) is the same as population distribution b) depends on how individuals are spaced in an area c) depends on the number of individuals in an area d) is equal to the number of individuals

Population distribution a) is the same as population density WB CHECK: Population distribution a) is the same as population density b) depends on how individuals are spaced in an area c) depends on the number of individuals in an area d) is equal to the number of individuals

POINT > Identify ways we describe populations 3. Growth rate: Positive growth rate means population is getting bigger; negative growth rate means population is shrinking Growth rate determines whether a population increases, decreases, or remains constant 4. Age Structure: Number of males/females at each age

POINT > Describe ways that populations change 1. Birth & Death Rate Birth > Death  Birth = Death  Birth < Death  Population Grows Population Constant Population Shrinks

The age structure of a population WB CHECK: What happens to a population when the birth rate is higher than the death rate? The age structure of a population is the average age of males and females describes how long individuals live is determined by the birth rate describes number of male and females at each age

POINT > Describe ways that populations change 2. Immigration & Emigration Immigration: Individuals move INTO a population range from elsewhere. This causes the population to grow

POINT > Describe ways that populations change Immigration & Emigration Emigration: Individuals move OUT of a population’s range. This causes the population to shrink

Birth Immigration Death Emigration

POINT > Describe two population growth patterns 1. Exponential population growth 2. Logistic population growth

POINT > Examine population growth patterns 1. Exponential growth: Each generation of offspring is larger than the one before it The larger the population gets, the faster it grows

POINT > Examine population growth patterns Exponential Growth: Number of Individuals Time

POINT > Examine population growth patterns Populations grow exponentially only under ideal conditions with unlimited resources

POINT > Examine population growth patterns 2. Logistic Growth: Period of exponential growth, followed by slower growth, and finally growth levels off

POINT > Examine population growth patterns Logistic growth: Number of Individuals Time

POINT > Examine population growth patterns Three phases of logistic growth Phase I – Exponential growth: population size & rate of growth increase rapidly

POINT > Examine population growth patterns Number of Individuals Time

POINT > Examine population growth patterns Three phases of logistic growth: Phase II – Growth slows Pop. size increases, but rate of growth decreases

POINT > Examine population growth patterns Number of Individuals Time

POINT > Examine population growth patterns Three phases of logistic growth: Phase III – Growth Stops Pop. size remains constant, rate of growth is zero

POINT > Examine population growth patterns Number of Individuals Time

What happens in stage I of logistic growth? WB CHECK: What happens in stage I of logistic growth? What happens in stage III of logistic growth? What happens in stage II of logistic growth? When can exponential growth occur?

POINT > Define carrying capacity Carrying capacity is the maximum number of individuals of a species a particular environment can support Carrying capacity may change based on many factors (biotic or abiotic factors)

is constant for a given ecosystem WB CHECK: Carrying capacity is constant for a given ecosystem can change if biotic or abiotic factors change is determined by birth rate is determined by death rate

Homework: Read Ch 5.1 pages 130-135 Assess #1-4 page 135 Workbook pages 324, 327, 334