Populations Objectives: Identify factors that contribute to population growth Describe exponential and logistic growth Compare and contrast density-dependent and density-independent limiting factors

All the members of a species located in the same area I. Population: All the members of a species located in the same area

II. Characteristics of Populations A. Density B. Dispersion 1. Uniform/ Regular 2. Clumped/ Aggregated ** 3. Random

III. Population Growth A. Growth rate determined by: 1. Births – Deaths 2. In a local population, also determined by: Immigration – Emigration B. Fastest rate a population can grow = Biotic Potential Limited by reproductive potential High for organisms that reproduce quickly, don’t care for young (Ex. Insects) Lower for organisms that have few offspring at once, care for young (Ex. Humans)

Population Growth… C. If conditions are favorable, populations continue to increase in size

III. Exponential Growth A. Population grows faster and faster B. Represented by J-curve

C. As population continues to increase, so does population density D. Needed materials begin to run out: Competition (think “survival of the fittest”): 1. Interspecific – between different species 2. Intraspecific - among members of the same species E. No population can continue to increase indefinitely Every environment has a carrying capacity

IV. Limiting Factors A. Keep a population from growing 1. Density-dependent: competition for resources, disease 2. Density-independent: natural disaster B. Can cause population decrease due to death or migration C. Lead to competition and natural selection

V. Logistic Growth A. As population approaches carrying capacity, growth rate slows 1. Births decrease 2. Deaths increase B. S-curve emerges C. Limiting factors

Can a population overshoot its carrying capacity?

Analyzing population data… http://www.khanacademy.org/partner- content/crash-course1/cc-ecology/v/crash-course- ecology-02