1. Dispersion spatial distribution of individuals within a population

2. Three types of dispersion.
Clumped
resources or living space are clumped,
or because of social behavior

3. Three types of dispersion.
Uniform (Even)
social interactions result in individuals getting as far away from each other as possible

4. Three types of dispersion.
Random
Ex: seed dispersal by winds or birds

5. Understanding Populations Population size # of individuals it contains
14.3 Population Density and Distribution
Understanding Populations
Population size
# of individuals it contains
Population density
How crowded a population is
# of individuals/unit of area or volume

6. Measuring Populations
14.4 Population Growth Patterns
Measuring Populations
Population Dynamics
change in size and composition over time
Birth rate, death rate, life expectancy
Population Growth Rate
Depends on birth, death, emigration (movement out of a population), and immigration (movement into a population)

7. 14.4 Population Growth Patterns
Survivorship curves
show the number of surviving members over time from a measured set of births.

8. 14.4 Population Growth Patterns
Exponential Model
Increases rapidly after only a few generations
Assumption
Birth rates & death rates remain constant no matter how large the population becomes
Populations cannot grow indefinitely because of availability of resources and accumulation of wastes

9. 14.4 Population Growth Patterns
Logistic Model
Accounts for the influence of limiting factors
Limiting factor – restrains the growth of a population
Birth rates decline and death rates rise as population grows
Carrying capacity – the # of individuals the environment can support over a long period of time
the birth rate equals the death rate and growth stops
Assumption
Carrying capacity is constant and does not fluctuate with environmental changes

10. 14.4 Population Growth Patterns
Logistic and exponential models are not accurate representations of real populations
They are tools used to study population growth and regulation

12. Population Regulation – Limiting Factors
14.4 Population Growth Patterns
Population Regulation – Limiting Factors
Density-independent factor – weather, floods, and fires
Reduce the population by the same proportion regardless of population size
Density-dependent factor – food shortages or nesting sites
Triggered by increasing population density

13. 14.5 Ecological Succession
KEY CONCEPT Ecological succession is a process of change in the species that make up a community.

14. 14.5 Ecological Succession
a sequence of biotic changes
damaged communities are regenerated
new communities arise in previously uninhabited areas

15. 14.5 Ecological Succession
There are two types of succession.
primary succession — started by pioneer species

16. 14.5 Ecological Succession
There are two types of succession.
2. secondary succession — started by remaining species