MB 3.1: Life in a community

MB 4.1: Population Dynamics

What was a Limiting Factor?What are the two types of limiting factors?• A factor that restrains the growth of a population

2 Types:Density DependentDensity Independent

• Populations cannot grow indefinitely because the resources they depend upon become scarce and wastes accumulate.

Journal: What are some things that you think may

be limiting factors???

Limiting Factors

Density-Independent Factors -Reduce the population size by the same proportion, regardless of the population’s size.

Ex. weather, flood, fires

Limiting Factors

Density-Dependent Factors -Reduce the population size and are triggered by increasing population density.

Ex. Shortage of food, nesting sites, resource limitations, Disease

The graph below is an example of a _______________ .

What is the limiting factor for plant growth that is studied in this tolerance curve?

Succession Primary Succession: occurs following an opening of

uninhabited, barren habitat without plants and topsoil.

Secondary Succession: occurs on preexisting soil after the environment has been disrupted

Population

• A population is a group of organisms that belong to the same species and live in a particular place at the same time.

• Ex. all the bass living in a pond during a certain period of time.

Properties of Populations

1. Population Size- the number of individuals it contains

COUNTRY POPULATION SIZE

PERCENTAGE

World 6,671,226,000 100%

China 1,323,324,000 19.84%

India 1,131,729,000 16.96%

United States 303,885,000 4.56%

Iceland 316,252 0.005%

Properties of Populations

2. Population Density- measures how crowded a population is. It is expressed as the number of individuals per unit of area or volume

Ex. U.S. states with greatest population density New Jersey and lowest population density Alaska.

Properties of Populations

3. Dispersion- the spatial distribution of individuals within a population.

Ex. random, clumped, even

Exponential Growth

• When a population increases rapidly, only after a few generations and the larger the population gets, the faster it grows.

• Exponential population growth forms a characteristic J- shaped curve

• Ex. Bacteria and flies

Limiting Factor

• A factor that restrains the growth of a population

Journal: What are some examples of limiting factors?

Limiting Factor

• A factor that restrains the growth of a population

In reality populations cannot grow indefinitely because the resources they depend upon become scarce and wastes accumulate.

Limiting Factors

1. Density-Independent Factors -Reduce the population size by the same proportion, regardless of the population’s size.

Ex. weather, flood, fires

Limiting Factors

2. Density-Dependent Factors -Reduce the population size and are triggered by increasing population density.

Ex. Shortage of food, nesting sites, resource limitations, Disease

Logistic Model of Pop. Growth• The logistic model builds on the

exponential model but accounts for the influence of limiting factors.

Logistic Model of Pop. Growth

• Carrying Capacity- the number of individuals the environment can support over a long period of time.

• A graph of logistic growth is S- shaped

Competition• Occurs when fundamental niches overlap• Species use the same limited resources.

– Competitive Exclusion

Resource Partitioning

Begin Succession Activity