Ecology of Populations

1. Ecology of Populations Chapter 46 Mader: Biology 8th Ed.

2. Outline • Scope of Ecology • Population Density and Distribution • Population Growth Models • Survivorship Curves • Age Distributions • Regulation of Population Size • Life History Patterns • Human Population Growth • Environmental Impact Mader: Biology 8th Ed.

3. Scope of Ecology • Ecology - Study of the interactions of organisms with other organisms and the physical environment. • Habitat - Place where an organism lives. • Population - All the organisms within an area belonging to the same species. • Community - All various populations interacting at same locale. • Ecosystem - Community of populations. Mader: Biology 8th Ed.

4. Ecological Levels Mader: Biology 8th Ed.

5. Density and Distribution of Populations • Population Density - Number of individuals per unit area or volume. • Population Distribution - Pattern of dispersal of individuals within the area of interest. • Ecologists want to analyze and discover what causes the spatial and temporal “patchiness” of organisms. • Limiting Factors are factors that particularly determine whether an organism lives in an area. Mader: Biology 8th Ed.

6. Uniform Distribution Mader: Biology 8th Ed.

7. Random Distribution Mader: Biology 8th Ed.

8. Clumped Distribution Mader: Biology 8th Ed.

9. Characteristics of Populations • Intrinsic Rate of Natural Increase (r) • If immigration (+) and emigration (-) cancel each other out, then population growth can simply be modeled by birth rate minus the death rate. Mader: Biology 8th Ed.

10. Population Growth Models • Exponential Growth • Number of individuals added each generation increases as the total number of females increases. • Biotic Potential - Maximum population growth that can possibly occur under ideal circumstances. • Environmental Resistance - All environmental conditions that prevent populations from achieving biotic potential. Mader: Biology 8th Ed.

11. Exponential Growth Curve Mader: Biology 8th Ed.

12. Exponential Growth Equation Mader: Biology 8th Ed.

13. Logistic Growth • Logistic growth occurs when environmental resistance comes into play and retards exponential growth. • Living populations must eventually come under the control of environmental resistance. Mader: Biology 8th Ed.

14. Logistic Growth Mader: Biology 8th Ed.

15. Logistic Growth Mader: Biology 8th Ed.

16. Carrying Capacity • Carrying Capacity is the maximum number of individuals of a given species the environment can support. • The closer the population to the carrying capacity, the greater the environmental resistance. • Biotic potential is having full effect and birthrate is a maximum during exponential growth. Mader: Biology 8th Ed.

17. Mortality Patterns • A cohort is composed of all the members of a population born at the same time. • Survivorship is the probability of newborn individuals of a cohort surviving to particular ages. • Survivorship Curves Mader: Biology 8th Ed.

18. Survivorship Curves Mader: Biology 8th Ed.

19. Survivorship Curves Mader: Biology 8th Ed.

20. Age Distributions • Populations differ according to what proportion of the population falls in each age category. • At least three structures possible. • Increasing • Stable • Decreasing Mader: Biology 8th Ed.

21. U.S. Age Distributions Mader: Biology 8th Ed.

22. Regulation of Population Size • Density - Dependent Factors • Number of organisms present influences the effect of the factor. • Competition • Predation • Density - Independent Factors • Number of organisms present does not influence the effect of the factor. • Natural Disasters Mader: Biology 8th Ed.

23. Life History Patterns • r - Strategists (Opportunistic) • Produce large numbers of offspring. • Small body size. • Early maturity • No parental care. • Density independent controls. • Good dispersers and colonizers. Mader: Biology 8th Ed.

24. Life History Patterns • k - Strategists (Equilibrium) • Produce small numbers of offspring. • Large body size. • Late maturity • Significant parental care. • Density dependent controls. • Specialists Mader: Biology 8th Ed.

25. Human Population Growth • Human population has an exponential growth pattern. • Doubling time currently estimated at 53 years. • Population Size • 1800 1 Billion • 1930 2 Billion • 1960 3 Billion • 2000 6 Billion Mader: Biology 8th Ed.

26. World Population Growth Mader: Biology 8th Ed.

27. Country Development • More-Developed Countries (MDCs) • Slow population growth. • High standard of living. • Completed Demographic Transition. • North America and Europe • Less-Developed Countries (LDCs) • Rapid population growth. • Low standard of living. • Latin America • Africa and Asia Mader: Biology 8th Ed.

28. Age Distributions • Age Structure Diagrams divide populations into three age groups. • Pre-Reproductive • Reproductive • Post-Reproductive Mader: Biology 8th Ed.

29. More-Developed Countries Mader: Biology 8th Ed.

30. Less-Developed Countries Mader: Biology 8th Ed.

31. Environmental Impact • Environmental impact of a population is measured in terms of: • Population Size • Resource Consumption Per Capita • Resultant Pollution Mader: Biology 8th Ed.

32. Environmental Impact Mader: Biology 8th Ed.

33. Review • Scope of Ecology • Population Density and Distribution • Population Growth Models • Survivorship Curves • Age Distributions • Regulation of Population Size • Life History Patterns • Human Population Growth • Environmental Impact Mader: Biology 8th Ed.

34. Mader: Biology 8th Ed.