Population Dynamics Population a group of individuals from

Population Dynamics Population – a group of individuals from the same species that live in a certain area.

Carrying Capacity *The largest population of a species that a specific area can support. * What determines the carrying capacity of an environment? Brick and Paper Towel Demonstration

Population Growth Graph

Exponential growth phase – population grows rapidly Lag phase – population is slowly increasing Steady state phase – population has reached its carrying capacity Decline phase – population decreases due to:

Density Dependent Limiting Factors *Factors that limit the size of a population more strongly as that population increases. * Disease Water Food Shelter/Space

• As the population grows, food, water, and shelter become harder to find. • Some of the animals will die when they can no longer find the items they need to survive. So the population size decreases. • Disease will spread more easily as the population grows due to the increased stress level of the organisms and the close contact. • This disease usually kills some animals and causes the population size to go down.

Effects of Decreased Space • When the population size increases resources become scarce. • Animals have to compete with each other for their food.

Intraspecific Competition When animals of the same species compete for the same resources.

Interspecific Competition When animals of the different species compete for the same resources.

Density Independent Limiting Factors *Factors that limit the size of a population but DO NOT depend upon the size of the population. * Hunting Natural Disasters A new species entered the area Logging

The Earth’s Carrying Capacity • Current Population of Earth: 6. 8 billion people as of July 1 st , 2009 • Why has it not stopped growing yet? • What might stop the human population from expanding? Let me get this straight…It’s our herd that needs to be “thinned”?