Population Dynamics

Describing Populations Geographic range – physical area inhabited by a population Population density – number of individuals per unit area Distribution – how the individuals are spaced out Random Uniform Clumped

Describing Populations Cont’d Growth rate – determines if the size of a population changes It can increase, decrease, or stay the same Age structure – number of males and females of each age in a population

Population Growth INCREASES (+) DECREASES (-) Birthrate Death Rate Immigration – when new individuals move IN to a population’s area Emigration – when individuals move OUT of the population area

Exponential Growth Example: Exponential growth – the larger a population gets, the faster it grows Ideal scenario - no disease, no competition, everyone dies of old age Example: Time # of Bacteria 1 1 minute 2 2 minutes 4 3 minutes 8 4 minutes 16 5 minutes 32 6 minutes 64 7 minutes 128 8 minutes 256

Exponential Growth (J-curve)

Limiting Factors Limiting factors– something that controls the growth of a population Density-dependent – depends on the size of populations in the community Competition, predation, disease Density-independent – affects populations, no matter the size Flood, drought, heavy snow, hurricane, wildfires

Carrying capacity Carrying capacity – the maximum number of individuals of a species that can survive in a specific environment

Logistic Growth (S-curve) Logistic growth – begins with exponential growth, but then slows down and then stops growing