1. Factors that regulate population size
Population Growth
Factors that regulate population size

2. Population Growth Patterns
Population Characteristics
Size
Density
number per area
Distribution
Uniform
Random
Clumped

3. Population Distributions
Random
Uniform
Clumped

4. Population Characteristics
Sex ratios
Age structure
Number of individuals in different age classes
Reproductive age
Pre-reproductive age
Post-reproductive age

5. Age Structure Diagrams

6. Growth Rate = (BR + ImR) – (DR + EmR)
Population Growth
Growth Rate
Factors that increase population sizes
Birth Rate (BR)
Immigration (Im)
Factors that decrease population sizes
Death Rate (DR)
Emigration (Em)
Growth Rate = (BR + ImR) – (DR + EmR)

7. Exponential growth
A stable rate of growth leads to exponential growth.
As the population size increases, the same percentage increase becomes a larger total increase.

8. Exponential Growth in a population
J-curve
Occurs when a population starts out small and
environmental conditions are ideal.

9. Factors that limit Growth
Physical, chemical and biological factors (biotic and abiotic) that limit the amount of growth
Space
Nutrients
Predators
All limiting factors together make up the “environmental resistance” and affect the carrying capacity of the environment

10. Logistic Growth Curve (S-curve)
Environmental Resistance determines Carrying Capacity
Logistic Growth Curve (S-curve)
Carrying Capacity can change when limiting factors change

11. Limiting Factors Shelford’s Law of Tolerance (p. 588)
Certain range of environmental conditions that will allow for maximum population growth
Density Independent factors affect a population regardless of its size
Abiotic factors: climate, space

12. Limiting Factors Density dependent factors
Population size can limit further population growth
Intraspecific competition
Food resources
Mates
Disease
Interspecific Competition
Predation

13. Demography The study of human populations Population Size
Population Density and Distribution
Age Structure
Sex Ratios

14. Human Population Growth
Human population growth has been greater than exponential.
Growth rate has increased over time (mostly because of lower death rates).
Global growth rate peaked at 2.1% in the 1960’s.

15. Global Human Population

16. Human Distribution

17. Effect of Age Structure on Population Growth

18. Age Structure Diagrams

19. Age Pyramid for United States

20. Age structures are very different in the developed and developing countries

21. Effect of sex ratios on population growth

22. What is the earth’s carrying capacity?
Carrying capacity is influenced by, but not defined by, environmental impact.
Environmental impact depends on more than population alone.
Technology can increase or decrease the impact.
Cause more consumption – or –
Exploit previously unavailable resources

23. Technological innovations that increased carrying capacity

24. Decline in Global Growth Rate

25. Is growth rate responding to environmental resistance?
What part of the growth rate equation is changing?
Is the change occurring fastest where resources are scarcest?
Is the change resulting in less environmental impact?

27. TFR correlates with social opportunity for women

28. Growth rates are unevenly distributed

29. Population is increasing fastest where the standard of living is lowest

30. Ecological Footprints
The amount of resources used per person can be expressed in terms of the amount of land needed to provide those resources

31. What does the future hold?