1. Basic Terms n Population: a group of individuals from the same species that all live in the same area at the same time. Ecology: the study of how populations interact with their environment.

2. Changes in whooping crane population at Wood Buffalo Park 200 160 120 80 40 0 1940 1950 1960 197019801990 2000 Number of cranes Year

3. Population Growth n Births and immigration add individuals to any population, while deaths and emigration remove them.

4. Population Growth n Basic models of population growth Continuous growth can be represented by the equation: N t = N 0 e r t

5. Discrete Growth (N t = N 0 t ) Population size (N) 800 600 400 200 0 800 600 400 200 0 01 2 3 4 01 2 3 4 Continuous Growth (N t = N 0 e rt ) = 1.6 r = 0.47 Time (t)

6. Population Growth n Exponential growth Growth continues indefinitely and is density-independent. Can occur for short intervals, but cannot be sustained.

7. Population size (N) 500 400 300 200 100 0 0 1 234 5 678910 Generations High r Moderate r Low r Very low r Exponential growth

8. Population Growth n Exponential growth No population can continue to grow indefinitely. At high densities, growth becomes density-dependent. All populations eventually reach the carrying capacity of their habitat.

9. Population size Carrying capacity Time

10. Case Studies Explaining How Population Size Changes Over Time n Humans exhibiting density-dependent growth n Recovery from trauma: The Exxon Valdez oil spill

11. 4–5 million 10,000 B. C. 80006000400020000 Year 0 1 2 3 4 5 6 1999: 6 billion 1900: 1.5 billion 1700: 600 million 1500: 400 million 1 A. D.: 150–200 million 2000 A. D. Human population (billions) Historical growth

12. 1998 Projections 195019701990201020302050 Year 12 11 10 9 8 7 6 5 4 3 2 Human population size (billions) Medium High Low Recent growth

13. 1992 Projections Fertility rate High Medium Low Projected population in 2050 12.5 billion 10.15 billion 7.8 billion The 1992 projections for 2050 are higher than those from 1998 primarily because the earlier projections did not account for the impact of AIDS.

16. Persistent oil in mussel beds…

17. …led to slow recovery in other species.

19. Population Structure n Age structure Developed nations have an age distribution that tends to be even. Developing nations have an age distribution that is bottom-heavy (mostly young individuals).

20. More-developed countries 1998 data 2050 projections 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 020 40 60 (In millions) Males Females

21. Less-developed countries 1998 data 2050 projections (in millions) Males Females 0 100 200 300 0 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 5 90 95 100

22. Population Structure n Geographic structure Many species exist as a metapopulation. Small, isolated populations, even those on nature reserves, are unlikely to survive over the long term.

23. A metapopulation is made up of small, isolated populations. Individuals Habitat patches

24. Although some subpopulations go extinct over time...

25. …migration can restore or establish subpopulations.

26. Demography and Conservation n Demography: the study of factors that determine the size and structure of populations through time.

27. Demography and Conservation n Life tables Summarize the probability that an individual will survive and reproduce in any given year over the course of its lifetime.

28. Age Type lll Type ll Number of survivors (N x ) 0.1 1 10 100 1000 Low survivorship High survivorship Steady survivorship High survivorship Low survivorship Three general types of survivorship curves Type l

29. Demography and Conservation n Life tables Contain useful pieces of information, such as survivorship, fecundity, and net reproductive rate.

30. Life table Age (x)Survivorship (l x ) Fecundity (m x ) 0 (birth) 0.0 1 2 3 3.0 4.0 5.0 0.33 0.2

31. Demography and Conservation n Life tables Can be used to make population projections and guide conservation programs.

32. Demography and Conservation n Population viability analysis (PVA) A model that estimates the likelihood that a population will avoid extinction for a given time period.

33. Demography and Conservation n Population viability analysis (PVA) Populations are considered viable if they have a 95% probability of surviving for at least 100 years.

34. Demography and Conservation n Population viability analysis (PVA) Currently being used by natural resource managers.