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Population Dynamics Unit 1: Ecology What would be some potential problems if a population became too big? Population Dynamics • Population: • All the individuals of a species that live together in an area Population Dynamics • Three Key Features of Populations •Size •Density • Dispersion Three Key Features of Populations Size: number of individuals in an area Three Key Features of Populations • Growth Rate: • Birth Rate (natality) - Death Rate (mortality) • How many individuals are born vs. how many die • Birth rate (b) − death rate (d) = rate of natural increase (r) Three Key Features of Populations Density: measurement of population per unit area or unit volume Pop. Density = # of individuals ÷ unit of space How Do You Affect Density? 1. Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites) 2. Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather) How Do Populations Grow? • Idealized models describe two kinds of population growth: 1. Exponential Growth 2. Logistic Growth How is Population Growth Predicted? Exponential Growth (aka “J-shaped” curve) occurs when population growth starts slow then increases rapidly. Logistic Growth (aka “S-shaped” curve) occurs when population growth reaches its carrying capacity due to limiting factors and levels off. Carrying Capacity • Carrying Capacity (k): • The maximum population size that can be supported by the available resources • There can only be as many organisms as the environmental resources can support How does an ecosystem work? • An ecosystem changes over time. Species replacement is characterized by an ecological succession in which one community slowly replaces another as the environment changes. • There are two types of succession: 1. Primary which is the colonization of new land which was never inhabited 2. Secondary, colonization of land that takes place after a natural disasters (hurricanes, earthquakes, etc) or human actions. Reintroduction of Organisms • The first organisms to inhabit an area are called pioneer species (lichen). • The 2nd group of organisms to inhabit the area are bacteria, protists, mosses, and fungi • The 3rd group include insects & arthropods • The 4th group include grasses, herbs, shrubs, & trees • http://www.youtube.com/watch?v=E0qdWoLdk1c Checkpoint #1 • Q: What are the 2 types of succession? • A :Primary and secondary • Q: The first group of species to inhabit an area are _________ example_____. • A: Pioneer species example lichen • Q: What are the last group of species to inhabit an area? • A: trees and grass Checkpoint #2 1. An active volcano under the ocean erupts, and the build-up of cooled lava eventually forms a new island. What type of succession will immediately occur on the newly formed island? A. primary succession C. both primary & secondary B. secondary succession D. no succession 2. A lack of food prevents further growth in a deer population. This is an example of a A. range of tolerance C. phonic zone B. limiting factor D. biome 3. When populations increase, resource depletion may result in A. exponential growth C. competition B. straight-line growth D. increase in predators Continued… 4. Type of population growth that reaches carrying capacity is called________. A. demography C. logistic B. exponential D. j- shaped 5. An example of a density dependent factor is __________. A. disease C. weather B. natural disaster D. seasonal cycles 6. An example of a pioneer specie would be_______. A. pine trees C. maple trees B. lichen D. shrub