Outline: Lecture 4

1. Outline: Lecture 4 Population Biology Population Growth Exponential Growth Limits of Growth Human Population Growth

2. Population Biology Population Definition A group of individuals of one species located in one place at one time

3. Population Measurement Abundance and Density Biomass Age Distribution (frequency distribution of males and females by age)

4. Population Processes Births Deaths Immigration Emigration

5. Population Growth N1 = N0 + B + I - D - E

6. Growth Rate = rate of additions - rate of subtractions Rate of additions = per capita rate of additions (b) * population size (N) Rate of subtractions = per capita rate of subtractions (d) * population size (N)

7. The net per capita rate of change (b - d) = r

8. Exponential Growth (Geometric Growth) Population change by a constant rate Graphical outcome (j-shaped curve)

10. Under ideal conditions (constant birth rates and constant death rates) r will reach the value rMAX = intrinsic rate of increase In nature, any factors that influence birth or death rates will influence r

11. Does exponential growth occur in nature? Bacteria in culture Algae blooms Pest eruptions Human populations

13. Estimating per capita rate of change Sequential population census data (expressed as a decimal fraction) or Percentage rate of change (expressed as a decimal fraction)

14. Annual World Percentage Growth Rate in the year 2000 = 1.4% Approximate net per capita rate of change = 0.014

15. Different countries have different per capita growth rates and different exponential doubling time projections

16. Limits on Growth Natural populations cannot grow without limit Populations stabilize or decrease after a period of increase The maximum sustainable population size for a given species in a given location is the carrying capacity (K) of that location

17. Logistic Growth Population growth limited by carrying capacity Compare to Exponential Growth model

18. The observed per capita rate of change is a function of rMAX,carrying capacity (K) and population size (N). range of 0.0 to rMAX

19. when N is very small, K-N is almost equal to K and r is almost rMAX when N is nearly equal to K, K-N is almost zero and r is almost 0.0 Logistic Growth Graphical Outcome (s-shaped curve)

21. Limits on human populations What are the Limiting Factors on Human Populations?

22. Limits on human populations Limiting factors Food Food distribution Living space Production constraints Environmental limits

23. Causes for population decrease War Famine Economic recession or depression Infectious diseases Natural disasters

25. Demographic Transition • Industrialized countries were not always slow growth populations • "early" societies: birth and death rates high • "developing" societies: death rate decreases • birth rate remains greater than death rate • "advanced" societies: birth rate decreases to the level of death rate

27. "Western Industrialized" nations completed transition 1850 - 1950 "Less Developed" nations are presently in the transition phase

28. Causes for decreases in death rates: Nutrition improvements Public health sanitation (water and sewage) Medical advances

29. Causes for decreases in birth rate: Socioeconomic change, economic development, industrialization Government commitment to family planning programs Infant mortality decreases

30. Causes for decreases in birth rate: Social status of women increases Education opportunities for women increase