1. Populations

2. 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?

3. Random, Uniform, or Clumped??

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

5. 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

6. 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 _________________

7. 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??

8. 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?