Populations

Describing Populations Geographic Range: Area inhabited by population Density: Number of individuals per unit area Distribution: How individuals are spaced within a population Random Uniform Clumped Growth Rate: Is population increasing, decreasing, or staying the same? Age Structure: Number of males and females of each age Why is this important?

Random, Uniform, or Clumped??

Population Growth Rate What factors affect growth rate?? Birthrate Death rate Immigration Emigration

Exponential Growth Definition: The larger a population gets, the faster it grows When does this occur? Under ideal conditions, with unlimited resources Sometimes also when an organism moves to a new environment – why? Think: food, space, predation, disease, waste products

Logistic Growth Definition: When a population’s growth slows and then stops, following a period of exponential growth. Why does growth rate slow? Birthrate ______________ Death rate ________________ Immigration _________________ Emigration _________________

Logistic Growth Curve Phase I: Exponential Phase Phase II: Growth Slows Phase III: Growth Stops Carrying Capacity: The maximum number of individuals of a species that a particular environment can support What factors stabilize the population here??

Limiting Factors Factors that control the growth of a population and determine the carrying capacity Density-Dependent Factors: Affect population significantly Only when population reaches a certain size Density-Independent Factors: Affect all populations in similar Ways, regardless of size and density How are “invasive species” affected by these factors?