Population Dynamics

A group of organisms of the same species that occupy an area.

One of the characteristics of living things is the ability to reproduce.

If environmental conditions are “favorable” then the number of individuals in population should increase from one generation to the next.

3 Characteristics of Populations

1) Geographic Distribution

2) Density

3) Growth Rate

4 Factors Effecting Population Size Births-

individuals born each yearDeaths-

individuals that die each year Immigration –

Movement of individuals INTO a population

Emigration-Movement of individuals OUT of a

population

Population Size-Growth Rate Birth rate- # individuals born Death rate- # individuals die Immigration- # of individuals move in Emigration- # of individuals move out IF:

BR + I = DR + E EquilibriumBR + I > DR + E Increasing BR + I < DR + E Decreasing

Biotic Potential Under “favorable” conditions, a species may reach its

biotic potential. Highest reproduction rate possible for a species

under “ideal” conditions. Ex) Houseflies:

Lay over 100 eggs Can reproduce at 1 month After 7 generations,

1 fly =15 billion flies!!!

Exponential GrowthPopulations size

increases dramatically over time.

Occurs: when resources (food) are abundant

Shape: J

Logistic Growth A population begins with a period of slow growth followed by a brief period of exponential growth before leveling off at a stable size

Occurs: because resources are limited

Shape: S Environmental

resistance limits size of a population.

Real population growth looks like this.

3 Phases: lagging, exponential, equilibrium

Factors Effect Growth Rate Size of Population “limiting factors” stop population from reaching biotic potential. (keeping the population in check)

The number of individuals in a population for a certain area is called population density.

Carrying Capacity Max # of individuals of a species that the environment can normally &

consistently support. Changes as the environment changes.