(Write the stuff in GREEN) How Populations Grow (Write the stuff in GREEN)

FOUR MAIN CHARACTERISTICS Populations FOUR MAIN CHARACTERISTICS Geographic Distribution The range or area inhabited by a population Density Number of individuals per unit area Varies from organism to organism and from biome to biome Growth Rate Age structure *

Let's Try Something! Population Density = Number of Individuals ÷ Unit Area Unit Area of Biology Room = ~72 m2 What is the population density in the biology room? What if our class moved to the gym (about 638 m2)…would the population density be the same? If not, what would it be?

Population Growth Three factors affect population size Number of births Number of deaths Number of individuals that leave or enter Immigration-movement of individuals into Emigration-movement of individuals out

Exponential Growth If a population has abundant space and food, AND is protected from predators and disease, then that population will multiply and the population size will increase Why isn’t the world overrun with bunnies or elephants? Exponential growth: occurs when the individuals in a population reproduce at a constant rate Under ideal conditions with unlimited resources, a population will grow exponentially

Logistic Growth As resources become less available, the growth of a population slows or stops Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth Carrying capacity: largest number of individuals an ecosystem can support

Growth Curves