1. Population Dynamics

2. Describing Populations
Geographic range – physical area inhabited by a population
Population density – number of individuals per unit area
Distribution – how the individuals are spaced out
Random
Uniform
Clumped

3. Describing Populations Cont’d
Growth rate – determines if the size of a population changes
It can increase, decrease, or stay the same
Age structure – number of males and females of each age in a population

4. Population Growth INCREASES (+) DECREASES (-) Birthrate Death Rate
Immigration – when new individuals move IN to a population’s area
Emigration – when individuals move OUT of the population area

5. Exponential Growth Example:
Exponential growth – the larger a population gets, the faster it grows
Ideal scenario - no disease, no competition, everyone dies of old age
Example:
Time
# of Bacteria 1
1 minute 2
2 minutes 4
3 minutes 8
4 minutes 16
5 minutes 32
6 minutes 64
7 minutes
128
8 minutes
256

6. Exponential Growth (J-curve)

7. Limiting Factors
Limiting factors– something that controls the growth of a population
Density-dependent – depends on the size of populations in the community
Competition, predation, disease
Density-independent – affects populations, no matter the size
Flood, drought, heavy snow, hurricane, wildfires

8. Carrying capacity
Carrying capacity – the maximum number of individuals of a species that can survive in a specific environment

9. Logistic Growth (S-curve)
Logistic growth – begins with exponential growth, but then slows down and then stops growing