Chapter 8 Population Change

1. Chapter 8Population Change

2. Overview of Chapter 8 • Principles of Population Ecology • Reproductive Strategies • The Human Population • Demographics of Countries • Demographics of United States

3. Principles of Population Ecology Population Ecology • Study of populations and why their numbers change over time. For example, what is the pattern of reproduction, and what is the pattern of mortality • Important for • Endangered species • Invasive species Population • Group of individuals of same species living in the same geographic area at the same time

4. Population Density Population density • The number of individuals of a species per unit area or volume at a given time • Ex: minnows per Liter of pond water Ovals below have same population, and different densities

5. Change in Population Size

6. Change in Population Size

7. Death rate Growthrate Emigration rate Birth rate Immigration rate Calculating Population Change Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 people r = (b – d) + (i – e)

8. Maximum Population Growth Intrinsic Rate of Growth (Biotic Potential) • Growth rate under ideal conditions • J- Shaped Curve (exponential growth)

9. Environmental Resistance Environmental limits (resistance) • Prevent indefinite reproduction • Unfavorable food, water, shelter, predation, etc. Carrying Capacity (K) • Maximum # of individuals an environment can support • Causes leveling off of exponential growth • S- shaped curve (logistic population growth)

11. Population Crash Overshooting carrying capacity can lead to population crash • Abrupt decline in population density

12. Factors That Affect Population Size Density Dependent Factor: • Factor whose effect on population changes as population density changes • Examples: • Predation • Disease • Competition • Sometimes cause Boom-or-Bust Population Cycles

13. Boom-Or-Bust Population Cycles

14. Case Study- Predator Prey Dynamics on Isle Royale As wolf population increases, moose population decreases (and vice versa)

15. Factors That Affect Population Size Density Independent Factors • Factors that affects population size, but is not influenced by changes in population density • Examples: • Killing frost • Severe blizzard • Fire • Hurricanes • Geologic events, etc.

16. k-selected vs. high growth rate slow growth rate small body size large body size early maturity late maturity short life span long life span large broods small broods little / no parental care high parental care Reproductive Strategies Life History Strategies r-selected

17. Reproductive Strategies

18. Survivorship

19. Some populations fit two curves Herring Gulls Type III & Type II

20. Human Population Demography • Science of population structure and growth Human Population since 1980 is J-shaped curve

21. Human Population Population clock

22. Population Increase in Mexico What can you tell me about this graph?

23. Projecting Future Populations Population is increasing Growth rate (r) has started to decline Projections for 2050 • Low = 7.7 billion • High = 10.6 billion • Most likely = 9.1 billion

24. Demographics of Countries

25. Demographics of Countries

26. Demographics of Countries Developed vs. Developing Countries Demographics

27. Demographics of Countries Developed vs. Developing Countries Demographics

28. Demographic Stages Pre-industrial Stage • Birth and death rates high • Modest population growth Transitional Stage • Lowered death rate • Rapid population growth Industrial Stage • Birth rate decline • Population growth slow Post Industrial Stage • Low birth and death rates • Population growth very slow

29. Demographic Stages

31. Age Structure • The number and proportion of people at each age in a population

32. Demographics of Specific Countries Examples:

33. Demographics of Specific Countries Examples:

34. Demographics of Specific Countries Examples:

35. World-wide 29% of human population is under age 15 Could cause large increase in birth rates

36. Demographics of the US

37. Education of Immigrants into US