Populations

Important Vocabulary 1. Birth rate: number of births in a population in one year 2. Death rate: number of deaths in a population in one year 3. Immigration: number of individuals that move into a population 4. Emigration: number of individuals that move out of a population Slide # 2

Populations and Their Growth 1.Growth Rate: the change in a population’s size –“A” = Lag phase; slow growth –“B” exponential growth –“C” transitional phase –“D” carrying capacity Slide # 3 Carrying capacity is NOT fixed for any population. It can change from one season to another. What affects carrying capacity? Disease, food availability, water availability, predators

Positive Population Growth 1. Occurs when birth rate is higher than the death rate 2. Usually occurs when conditions are ideal; will increase until something stops it Human Population Growth Curve Slide # 4 Technology has greatly influenced the carrying capacity of human populations

Negative Population Growth 1.Occurs when birth rate is lower than death rate a.Ex. Overgrazing and drought left this area with out enough resources to sustain all of the wildlife. b.individuals die and the population decreases. Slide # 5

Population Cycles: Boom & Bust The human population experienced a boom (baby boom) after world war II. Slide # 7 Boom Bust Boom: Birth rate is higher than death rate Bust: Birth rate is lower than death rate

Limiting Factors: Limit Population Growth Slide # 8 Limiting factors: help stabilize population numbers when the population reaches carrying capacity for that ecosystem a.Density independent: factors that affect all members of the population equally if population is dense or not.  Natural disasters: floods, wildfires, tornadoes, pollution, habitat destruction b.Density dependent: factors that affect crowded populations  EX: competition, predation, crowding and stress, parasitism, and disease  Competition for limited resources is the most important limiting factor that affects carrying capacity.

What type of limiting factor is shown in each picture? Density Independent Density Dependent Density Independent Density Dependent