1. Chapter 35: Population Growth

2. Ecologists study the relationship between biotic and nonbiotic factors at 5 levels: A. Organisms B. Populations C. Communities D. Ecosystems E. Biosphere II. Levels of Organization

3. A. Population Definition: a group of individuals of the same species living in a particular area at the same time

4. B. Population density = # of individuals ------------------ unit area of space

5. How do you calculate population density? Example: If there are 10 red tail hawks in a 5 mile 2 piece of land, what is the density of hawks per mile 2 ? A: 10 ÷ 5 = 2 hawks/mi 2

6. A. Exponential Growth  Definition: under ideal conditions with unlimited resources, a population will grow exponentially Occurs when the individuals in a population reproduce at a constant rate. J CURVE!

7. C. Logistic Growth  Exponential growth does not continue for very long  Growth slows or stops as resources become less available Logistic growth occurs when a population's growth slows or stops following a period of exponential growth

8. E. Carrying Capacity  Carrying capacity is the largest # of individuals of a population that an environment can support

9. F. As a population approaches Carrying Capacity, average growth rate reaches ZERO (levels off) Carrying capacity (K) Pressure begins due to environmental resistance Lag phase Population Numbers Time

10. Limiting Factors  Factor that causes population growth to decrease Density-Dependent limiting factor that depends on population size Density-Independent affects all populations in similar ways, regardless of the population size

11. Density-Dependent Factors  A limiting factor that depends on population size  Food, clean water  competition  predation  parasitism  disease

12. Density-Independent Factors  Affect all populations in similar ways, regardless of the population size  unusual weather  natural disasters  seasonal cycles  certain human activities— such as damming rivers and clear-cutting forests

13. Human Population Growth

15. A. Human population began growing more rapidly about 500 years ago because life was made easier and safer by advances in agriculture and industry

16. B. Life improved for humans (and death rates reduced) due to: Improved sanitation Medicine and healthcare Birthrates remained high

17. With these advances, human population experienced exponential growth C. Factors that affected pop growth: - Agriculture - Bubonic Plague - Industrial Revolution

18. WHAT TREND DO YOU SEE ON THIS SLIDE COMPARED TO NEXT SLIDE?

20. E. Current population and beyond * There are currently 7.1 BILLION people in the world * By the time you are in your 50’s, it is estimated there could be up to 9.6 BILLION! Source: UN.org Report World Population Projections, June 2013 link

21. Negative population growth has been seen in: Germany, Japan, and Russia among other countries. Growth in U.S. & much of Europe has slowed dramatically

22. In the Future F. Ecologists suggest that if growth does not slow down, there could be serious damage to the environment and global economy. G. How can population growth be helped? Science Technology Use of contraceptives Smaller family sizes Starting family at older age Education