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CHAPTER 52

CHAPTER 52 . POPULATION ECOLOGY. Characteristics. Density Distribution Size Age Structure. Density. Direct Counts- Larger, less numerous organisms Plankton Population Sampling Time x velocity x diameter = M 3 Total # of plankton/ M 3 = # plankton per M 3

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CHAPTER 52

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  1. CHAPTER 52 POPULATION ECOLOGY

  2. Characteristics Density Distribution Size Age Structure

  3. Density • Direct Counts- • Larger, less numerous organisms • Plankton Population Sampling • Time x velocity x diameter = M3 • Total # of plankton/ M3 = # plankton per M3 • 75 plankton/0.5 M3 = 150/M3 • Mark & Recapture- many animals • Aerial Surveys – • Line transects etc. • observe large areas, large animals by sight • Mist nets for migrating birds

  4. Mark & Recapture # marked in 1st catch = # recaptures in 2nd catch Population total total # in 2nd catch OR: N = # marked in 1st catch x total # in 2nd catch # of recaptures in 2nd catch # marked = 50 Total in 2nd catch = 100 # recaptures = 10 N = 50 x 100/10 N = 500

  5. Dispersion • How the individuals are arranged in the landscape. • Uniform – • all parts of the habitat suitable, but has intra-specific competition • Random • all parts of habitat suitable • Clumped- • Habitat is patchy or • Social behaviors

  6. Dispersion

  7. Population Size Starting size of population Add: Births and immigration Subtract: Deaths and emigration Gives the New population size,

  8. Population Growth

  9. Exponential Growth Growth curve for field Mice in a cornfield

  10. Exponential Growth • Biotic Potential – Pop. Grows as fast as physiology allows. • Unlimited resources • No pollution build up • Ideal conditions • Short lived period • Often quickly die out, colonize new areas • R selected species Population size (N) Time (t) Exponential Growth Fig. 9.4, p. 201

  11. Logistic Growth

  12. Logistic Growth • Slower initial growth • Long –term stable pop. At carrying capacity (K). • K is size of pop. Area can sustain. • Growth slowed by limiting factors K Population size (N) Time (t) Logistic Growth

  13. Fig. 32.2

  14. Population Limiting Factors • Density dependent factors • Competition • Predation • Stress/crowding • Waste accumulation • Disease • Space • Resources • Density independent factors • Weather/climate • Periodic disturbances

  15. Population Life History Strategies K R

  16. Type III (R selected) Short maturation & lifespan Many offspring No parental care High death rate Type I (K selected) Long maturation & lifespan Few offspring Extensive parental care Low death rate Type I vs Type III

  17. K-Selected Species elephant saguaro Fewer, larger offspring High parental care and protection of offspring Later reproductive age Most offspring survive to reproductive age Larger adults Adapted to stable climate and environmental conditions Lower population growth rate (r) Population size fairly stable and usually close to carrying capacity (K) Specialist niche High ability to compete Late successional species

  18. r-Selected Species cockroach dandelion Many small offspring Little or no parental care and protection of offspring Early reproductive age Most offspring die before reaching reproductive age Small adults Adapted to unstable climate and environmental conditions High population growth rate (r) Population size fluctuates wildly above and below carrying capacity (K) Generalist niche Low ability to compete Early successional species

  19. European Kestrals

  20. r selected • Population grows at biotic max • Lots of offspring • Little parental care • Reproduce early, often K selected • Population adapted to being at carrying capacity • Few offspring • Lots of parental care • Reproduce late, infrequently

  21. Testingahypothesis

  22. Human Population GrowthorGo Forth and Multiply

  23. Human Population growth • For most of our history a logistic curve. • Currently exponential growth • Not uniform around the globe • Developing nations growing fastest • What has made the change possible? • Drop in death rate. Birth rate has fallen, not increased. • How long will this be sustainable? • Future predictions for growth?

  24. Human Population Growth

  25. World – Wide Trend?? • Growth rates differ within and between countries:

  26. Births per woman Births per woman < 2 4-4.9 2-2.9 5+ Data not available 3-3.9

  27. Infant deaths per 1,000 live births <10 10-35 36-70 71-100 100+ Data not available Infant deaths

  28. Population Growth Annual world population growth <1% 1-1.9% 2-2.9% 3+% Data not available Fig. 11.3, p. 240

  29. Income and country GNP per capita, 1998 Low income (Under $1,000) Middle income ($1,000–$10,000) High income (Above $10,000) Fig. 1.5, p. 9

  30. General age structure diagrams Rapid Growth Slow Growth Zero Growth Negative Growth

  31. Males Females Males Females Canada United States India Australia Mexico China

  32. Age Females Males 24 24 24 20 Millions Millions Millions Millions 20 24 24 24 1955 1985 2015 2035 USA age structure Diagrams Yellow= Baby Boomers

  33. NOW WHAT?

  34. Where we are: • 1930, 2 billion • September 1999, 6 billion • 3 people every second • 250,000 every day • 87 million every year • 12 billion by 2050 • 8 Billion- if slower rate

  35. Influence on environment • More land for agriculture, resource exploitation • More land for cities, roadways, suburbs • Less fish in the sea for the food chain • Deforestation • Oil, gas won’t last forever • Pollution builds up • Better “green” technologies? • Heightened awareness, concern? • Better understanding of ecosystems?

  36. Human domination of landscape Arctic Circle Arctic Circle Tropic of Cancer Equator Tropic of Capricorn Human disturbance Antarctic Circle Predominantly natural Partially disturbed Human dominated

  37. Every second… 5 people are born and 2 people die, a net gain of 3 people.

  38. Improved medical care has dramatically reduced infant mortality and mortality of women during labor.

  39. Demographic transition • Larger urban families cost more, birth rate drops • Population now much larger, slows its growth rate • Influence of other (cultural, religious) pressures can slow birth rate decline • Women often lack freedom to determine family size, education employment opportunities

  40. Demographic transition • Death rate (infant mortality) drops first • Birth rate remains constant • Population increases quickly • Economy transitions from agriculture to urban

  41. Stage 1 Preindustrial Stage 2 Transitional Stage 3 Industrial Stage 4 Postindustrial relative population size births deaths low increasing decreasing low zero negative very high

  42. USA demographic transition & population size 32 30 28 26 24 Births per thousand population 22 20 World War II 18 Demographic transition 16 Baby bust Depression Baby boom Echo babyboom 14 0 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year

  43. 4.0 3.5 3.0 2.5 Births per woman 2.1 2.0 1.5 1.0 0.5 0 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Total fertility rates in USA 1917-2000 Baby Boom (1946-64) 1975 on ….Below native replacement rate- immigration keeps population growing

  44. Legal immigration to the United States between 1820 and 1997 1907 1914 New laws restrict immigration Great Depression

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