4 CHARACTERISTICS OF A POPULATION 1.Geographic Distribution/ Range- How much area does the population cover? 2.Density- How many members of the population are found in the range? Usually #/ km 2 or #/ mi 2

3. Growth Rate- is the population growing, declining, or stable? 4. Age structure- What fraction of the population is what age?

HOW POPULATIONS CHANGE Births and deaths add or subtract numbers from a population Emigration, movement of individuals out, can subtract population numbers. Immigration, movement in, add to populations.

EXPONENTIAL GROWTH Occurs with limitless resources. Constant reproduction. Creates a J curve.

LOGISTIC GROWTH When resources become less available, growth slows. Population size reaches a carrying capacity. Forms an S curve.

LIMITING FACTORS Factors such as competition, predation, parasitism, and disease that change with population size are density dependent limiting factors. Factors such as weather, natural disasters, seasonal cycles, or human activities are density independent factor s.

DIVERSITY INDEX Statistical tool showing population makeup of an ecosystem. All percentages add up to 100%. Species Diversity= # of members of species total # of species