1. Populations

2. Review
Remember a population is a group of individuals that belong to the same species and live in the same area

3. Population Density
Population density refers to the number of organisms per unit area
Spatial Distribution
Dispersion is the pattern of spacing of a population.
Clumped
Random
Uniformed/Spaced

5. Population Dynamics Factors that affect a population’s size: Natality
Birth Rate
Mortality
Death Rate
Immigration
Movement of individuals INTO an area
Emigration
Movement of individuals OUT of an area

6. Population Growth
Growth rate is determined by looking at the change in number of individuals over time
Population Growth
natality > mortality
immigration > emigration
Population Stability
natality = mortality
Immigration = emigration

7. Exponential Growth
This occurs when members of a population reproduce at a constant rate.
Unrestricted growth
Result is a “J-shaped” curve
Population would become infinitely larger until a limiting factor slows the growth

8. Logistic Growth
As resources become less available, the growth of a population slows.
Restricted Growth
“S-shaped” curve
A population will reach it’s carrying capacity

9. Comparison

11. Carrying Capacity
The maximum number of individuals in a species that an environment can support for the long term
Carrying capacity is limited by the energy, water, oxygen, nutrients available or other limiting factors

12. Limiting Factors
Any condition of the environment that limits the size of a population
2 major groups
Density-Dependent
Density-Independent

13. Density-Dependent When a limiting factor depends on population size
Density-dependent factors only become limiting when the population density reaches a certain level
Competition for food, water, space, sunlight, etc. can happen between 2 individuals of the same or different species

14. Density-Independent
Affect ALL populations (large and small) in similar ways.
Caused by human disturbance, natural disasters, seasonal cycles, etc
Some density-independent limiting factors could severely upset the growth of a population.

15. Review What are the 3 types of dispersion?
Random, Clumped, Uniform/Spaced
What is natality? What is emigration?
Birth Rate. Movement OUT of an area.
What are the 2 types of growth curves?
J-shaped & S-shaped
What is carrying capacity?
The max number of individuals that can be sustained in an area.

16. Any Questions?