1. Population Biology

2. Density and Distribution
How Study Populations?
Geographic Range
Density and Distribution
Growth rate
Age structure

3. Geographic Range The area inhabited by a population
Can vary greatly depending on the species
 (bacteria on a rotting pumpkin vs. cod in the western Atlantic ocean from Greenland to North Carolina

4. Density and Distribution
Population density refers to the number of individuals per unit area
Distribution refers to how individuals in a population are spaced out across the range of the population:  random, uniform or clumps.
Random
Uniform
Clumped

5. Growth Rate Age Structure
Determines whether the size of the population increases, decreases, or stays the same.
 can be positive, negative or zero
Age Structure
The number of males and females of each age a population contains
Important because most animals do not reproduce until a certain age

6. Factors that effect population growth
1. Birth Rate and Death Rate
In a given period of time:
Birth rate > death rate  population increases
Birth rate = death rate  population stays the same
Birth rate < death rate  population decreases
2. Emigration and Immigration
Immigration – movement of individuals into an area occupied by an existing populations
Emigration – movement of individuals out of an area

7. Exponential vs. Logistic Growth Would you take the money?
Exponential Growth
Under ideal conditions with UNLIMITED resources, a population can and will grow exponentially.
Exponential growth is when a population increases exponentially Xn (often doubling)

8. Logistic Growth
Resources are NOT unlimited so a population can not grow exponentially forever
Logistic growth occurs when a populations’ growth slows and then stops, following a period of exponential growth
Carrying Capacity
The maximum number of individuals of a particular species in a particular environment can support (without degrading it for future generations)

9. * Population will hover around the CC