1 / 28

General Population Change

General Population Change. Chapter 8a Raven and Berg. Controls. A society which practices death control must at the same time practice birth control. John Rock (1963). I. Population- . Populations Change in size. Rates of Change: Birth rate (b) – number of births per 1000 people per year

mishmael
Download Presentation

General Population Change

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. General Population Change Chapter 8a Raven and Berg O'Connell: General Population 8a

  2. Controls A society which practices death control must at the same time practice birth control. John Rock (1963) O'Connell: General Population 8a

  3. I. Population-

  4. Populations Change in size • Rates of Change: • Birth rate (b) – number of births per 1000 people per year • Death rate (d) – number of deaths per 1000 people per year • Growth rate (r) – birth rate minus death rate • r = b – d O'Connell: General Population 8a

  5. Global Population Changes How Do Populations Change in Size? On a global scale (closed system): O'Connell: General Population 8a

  6. Local Population Changes Immigration (i) – individuals move into a population Emigration (e) – individuals exit a population At a local level (e.g. national) O'Connell: General Population 8a

  7. Death rate Growth rate Emigration rate Birth rate Immigration rate Local rate of change How Do Populations Change in Size? Local scale: r = (b – d) + (i – e) O'Connell: General Population 8a

  8. Examples of r • Population of 10,000 • 200 births per year (or 20 births per 1000 people) • 100 deaths per year (10 per 1000 people) r = 20/1000 – 10/1000 r = 0.02 – 0.01 = 0.01 OR 1% per year O'Connell: General Population 8a

  9. population growth controls • Unchecked population growth • Biotic potential – capacity for growth • Intrinsic rate of increase – the rate at which a population would grow if it had unlimited resources O'Connell: General Population 8a

  10. Exponential growth • Fast rate • Optimal conditions • J-curve O'Connell: General Population 8a

  11. Environmental Resistance • Consists of all the factors acting jointly to limit the growth of population • Limited availability of essential resources • Disease and predation O'Connell: General Population 8a

  12. Carrying capacity (K) • The largest number of individuals (N) of a population that a given environment can support • Causes leveling off of exponential growth • S-shaped curve of logistic population growth • Dynamic • Biotic potential and environmental resistance determine carrying capacity (K) O'Connell: General Population 8a

  13. O'Connell: General Population 8a

  14. Logistic growth • Number of individuals (N) is near the carrying capacity (K) of the environment stabilizes • S - curve O'Connell: General Population 8a

  15. Overshooting Overshooting the carrying capacity can lead to a population crash. O'Connell: General Population 8a

  16. 20 / 25 m2 20 / 100 m2 Population Density • Population density • Number of individuals of species per unit of area • D=m/v O'Connell: General Population 8a

  17. Population Dispersion Spatial pattern of distribution O'Connell: General Population 8a

  18. Variations Boundaries must be defined May vary in a single habitat, season to season, or year to year Changes over time Environmental pressures O'Connell: General Population 8a

  19. Density-Dependent Factors • As population density increases, density-dependent factors tend to slow population growth • Predation • Disease • Competition • Easier to find mates and may offer protection from predators O'Connell: General Population 8a

  20. Cycles Density-Dependence and Boom-or-Bust Population Cycles O'Connell: General Population 8a

  21. Predatory Prey Dynamics on Isle Royale Early 1900s, moose move across frozen Lake Superior to island. Wolf and moose populations follow one another between increase and decrease. Density dependent O'Connell: General Population 8a

  22. Density-Independent Factors • Regardless of population density • Usually abiotic • Weather • Fire • Other natural disasters O'Connell: General Population 8a

  23. Case-in-point: Arctic mosquitoes . • When it is warm, a lot of mosquitoes. • When it gets cold, adult mosquitoes die. O'Connell: General Population 8a

  24. Reproductive strategies • Influencing factors: • Age reproduction begins • Length of time reproductive age lasts • Periods of reproduction per lifetime • Number of offspring per reproduction O'Connell: General Population 8a

  25. K – selected Life history strategies r - selected Opportunists Short life span High intrinsic rate of increase Lower evolutionary scale Competitors Long life span Low intrinsic rate of increase High evolutionary scale O'Connell: General Population 8a

  26. r-selected species • Early reproductive age • Many small offspring • Little/no parental care • Most offspring die before maturation • Early maturity • Small adults • Short life span • Examples: algae, bacteria, rodents, insects and annual plants O'Connell: General Population 8a

  27. K-selected species • Later reproductive age • Few, large offspring • High parental care • Most offspring reach reproductive age • Late maturity • Larger body size • Longer life span • Examples: large mammals (e.g. whales and humans), birds of prey, large and long-lived plants (e.g. saguaro cactus and redwood trees) O'Connell: General Population 8a

  28. Life expectancies • Survivorship curve – the number of survivors of each age group for a particular species • 3 types of curves O'Connell: General Population 8a

More Related