1. Human Population
4.2

2. Population Growth Is Limited
Limiting Factor: factor that causes population growth to decrease
2 kinds of limiting factors
Density-Dependent Factors: depends on populations size
Density-Independent Factors: affect all populations in similar ways, regardless of size

3. Density Dependent Limiting Factors
Density: the number of organisms per unit area
Competition
Predation
Parasitism
Disease
Be able to explain why these factors are present in crowded populations (hi-density populations)

4. Predator-Prey Relationship
Explain the diagram below:

5. Density Independent Limiting Factor
Affects all populations in the same way, regardless of size
Unusual weather
Natural disasters
Human activities
Seasonal cycles
Can you give an example for each listed above?

6. Human Populations
In history, human population remained constant (no growth or decline)
High birth rate and high death rate

7. Population Growth Goes Exponential!
200 years ago, human population began to explode…
Agriculture
Industry
Medicine
Improved Sanitation
Healthcare
This drastically reduced the death rate, but didn’t change birth rate

8. Modeling Growth Demography: Scientific study of human populations.
Observation: US, Japan, Europe growth slows.
Experiment: collect data (US Census)
Model: “Demographic Transition” Hypothesis

9. Demographic Transition
:A dramatic change in birth rate and death rate
Stage 1: High birthrate and high death rate
Most countries in early history
Stage 2: High birthrate and low death rate
US ( ), developing countries
Stage 3: Low birthrate and low death rate
US (now), Europe.
State 4: Population decreases, birthrate lower then death rate. - Japan

11. Age Structure Diagrams
Population profiles to predict future growth
STABLE
DECLINE
RAPID GROWTH

12. Mini-Quiz