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# Population ecology part 1

Introduction to Populations
Published on: Mar 4, 2016
Published in: Education

#### Transcripts - Population ecology part 1

• 1. (Modern Biology: Chapter 19) Population Ecology
• 2. Properties of Populations  Population: a group of organisms of one species in the same area at the same time (defined space and time)  1) Population Size = number of individuals  Can be difficult to measure directly
• 3. Properties of Populations 2) Population Density = how crowded a population is  Expressed as # of individuals per unit area or volume  Ex: United States Population Density (Homo sapiens) 30 people/km2
• 4. Properties of Populations (con’t)  3) Dispersion = the spatial distribution of individuals  3 types: A) Uniform (aka. Even) B) Clumped C) Random
• 5. Population Growth Rate  All populations are dynamic. They change in size and composition over time.  Scientists who study population dynamics = DEMOGRAPHERS  GROWTH RATE of a population is the amount by which a population’s size changes in a given time. Can be positive (Increasing population over time)
• 6. Exponential Growth  Describes a population that grows rapidly after only a few generations  “J-curve”  Larger population = faster growth  In reality, resources will run out  Limiting Factor: a factor that restrains population growth  ALL populations are ultimately limited by their
• 7. Population Regulation  Two type of limiting factors have been identified: 1) Density-independent: population density does not matter  i.e. weather, floods, fires, climate change  The population is reduced by the same proportion regardless of size/density 2) Density-dependent: depend on population density  i.e. availability of resources, space
• 8. Logistic Growth  Describes a realistic population  Accounts for limiting factors  “S-Curve”  Carrying Capacity: the maximum # of individuals the environment can support over time