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Populations

Populations . Chapter 19. Populations . Group of organisms of the same species that live in the same place at the same time. Basic terms. Population size- the number of individuals Population density- the number of individuals in a given area or volume

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Populations

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  1. Populations Chapter 19

  2. Populations • Group of organisms of the same species that live in the same place at the same time

  3. Basic terms • Population size- the number of individuals • Population density- the number of individuals in a given area or volume • Dispersion- spatial distribution of individuals within a population

  4. Dispersion patterns Clumped Uniform Random

  5. Population dynamics

  6. Population Dynamics • Birth rate (b) • Death rate (d) • Growth rate per capita (r) • Population growth rate (G) • Population size (N) • Carrying capacity (K) • Survivorship • r=b-d

  7. Population Dynamics Other factors • Immigration • Emigration • Age structure • Patterns of mortality • Survivorship curves

  8. Survivorship Curves: 3 strategies

  9. Population growth rate • Depends on four processes • Birth • Death • Immigration • Emigration • Two models • Exponential • Logistic Usually considered to balance each other out and are rarely used in actual calculations

  10. Exponential Growth Model • Start with ideal • Assume infinite space and resources • J-shaped curve • G=rN

  11. Logistic Growth Model • Ideal population growth that is slowed by limiting factors • S-shaped curve • G=rN(K-N)/K

  12. Factors limiting population growth • Density dependent factors • As population grow, birthrates decrease (per capita) and death rates rise • Competition for limiting resources • Sanitation/ spread of disease • Seasonal growth • Annuals and many insects

  13. Boom and Bust cycles • Regular fluctuations in population size

  14. Life History • Traits that affect the schedule of reproduction and death • Key characteristics • Age of first reproduction • Frequency of reproduction • Number of offspring • Parental care

  15. Population Growth • Exponential growth • Logistic growth

  16. Population Growth if K is exceeded

  17. Population Regulation • Density independent factors • Weather, fire • Density dependent factors • Food, water, nesting sites

  18. Perils of Small Populations • Bottleneck effect • Reduced genetic variation • Increases inbreeding

  19. R-selection • Usually small organisms • Short lived • Rapid development of sexual maturity • Large numbers of offspring • Little to no parental care • Abundant resources available • Unstable environments

  20. K-selection • Usually large organisms • Long lived • Slow development to sexual maturity • Produce few offspring • Parental care is extensive • Stable environment

  21. Measuring Population Size • Sampling methods • Simple random sampling • Stratified sampling • Cluster sampling • Systematic sampling • Two-stage sampling

  22. Simple random sampling • A set number of samples (n) is taken from a large population (N)

  23. Stratified sampling • Population (N) is broken into small pieces and a random sample (nx) is taken from each piece. • 3 samples were taken from each of the 16 blocks

  24. Cluster Sampling • Population (N) is broken into small pieces and all organisms in randomly selected pieces are counted

  25. Systematic sampling • Population (N) is broken into small groups and every kthgroup is sampled

  26. Two-stage Sampling • Using more than one sampling method at a time

  27. Human Populations

  28. Are we responsible for the care of the planet, or just another species vying for resources? “…and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth.” (Genesis 1:29) And the LORD God took the man, and put him into the garden of Eden to dress it and to keep it. (Genesis 2:15)

  29. Factors we need to watch • Sustainability • Governmental policies • Demographic transitions • Age structure • Ecological footprint

  30. Sustainability • Sustainable yield- harvesting resources at a level that allows replenishment equal to depletion Northern Cod Collapse

  31. Sustainability • There is a K value for human population • Difficult to determine as it changes with new advances in medicine and technology (especially agriculture)

  32. Governmental Policies Dominican Republic Haiti

  33. Demographic Transition

  34. Demographic Transition • Stage 1: Preindustrial • Malthusian • Population highly dependent on resource availability • High birth and death rates

  35. Demographic Transition • Stage 2: Transitional • Agriculture stabilizes food supply • Medical care lowers death rate (especially children) • Vaccines • Sewage • Birth rate remains high

  36. Demographic Transition • Stage 3: Industrial • Birth rate further decreases • Urbanization decreases need for children • Female literacy (and value) increases • Birth control available • Generation span lengthens • Death rate decreases • Better health care for all

  37. Demographic Transition • Stage 4: Post-industrial • Birth rates low • Death rates low

  38. Demographic Transition • Stage 5: Aging Population • Birthrate is below death rate • Actually beginning to occur in western Europe and some eastern Asian countries • Effects are theoretical and somewhat controversial

  39. Age Structure Developed Countries Developing Countries

  40. 250 million  500 million 1492 years 500 million  1 billion 310 years 1 billion  2 billion 118 years 2 billion  4 billion 52 years 4 billion  8 billion (est.)44 years

  41. Human Population

  42. Demographic Transition

  43. Demographic Transition • Stage 1: Preindustrial • Malthusian • Population highly dependent on resource availability • High birth and death rates

  44. Demographic Transition • Stage 2: Transitional • Agriculture stabilizes food supply • Medical care lowers death rate (especially children) • Vaccines • Sewage • Birth rate remains high

  45. Demographic Transition • Stage 3: Industrial • Birth rate further decreases • Urbanization decreases need for children • Female literacy (and value) increases • Birth control available • Death rate decreases • Better health care for all

  46. Demographic Transition • Stage 4: Post-industrial • Birth rates low • Death rates low

  47. Demographic Transition • Stage 5: Aging Population • Birthrate is below death rate • Actually beginning to occur in western Europe and some eastern Asian countries • Effects are theoretical and somewhat controversial

  48. Human Population Growth • 2011 Estimates • 135 million births per year (4.3 births/sec) • 57 million deaths per year • Net of 78 million more people in 2011 • World population

  49. 80% of people live in stage 1 and 2 countries20% of people live in stage 3 and 4 countries

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