1. POPULATIONS & CARRYING CAPACITY 02 June 20101Populations.ppt

2. Population number of individuals of a species in a defined place and time. 02 June 2010 2Populations.ppt

3. Dynamic characteristics of populations Size, number of individuals (N) Density (N/ area) Dispersion, – Random, uniform, clumped, (appropriate scale) 02 June 2010 3Populations.ppt

4. Dynamic characteristics of populations Age distribution, – proportions of young, middle-aged, old – Differs in growing, stable, decreasing populations 02 June 2010 4Populations.ppt

5. Changes in populations Growth Decline May affect size, density, dispersion, age distribution. May be affected by size, density, dispersion, age distribution. 02 June 2010 5Populations.ppt

6. Changes in populations Growth – Expansion of species populations may lead to evolution of new species Decline – Shrinking species populations may lead to extinction Small populations Narrowly specialized species 02 June 2010 6Populations.ppt

7. Changes in populations ΔN = +B +I –D –E – +B = births (birth rate) – +I = immigrants (immigration rate) – – D = deaths (death rate) – – E = emigrants (emigration rate) – (For many [most] natural populations I and E are minimal.) 02 June 2010 7Populations.ppt

8. Population growth – B > D – Exponential growth, dN/dt = rN N = number, pop.size r = biotic potential, intrinsic rate of increase. 02 June 2010 8Populations.ppt

9. Population growth Exponential growth unlimited – dN/dt = rN Unrealistic

10. Population growth Logistic growth, – dN/dt = rN (1 - N/K) N = number, population size r = biotic potential, intrinsic rate of increase. K = carrying capacity – Better represents real populations

11. Population growth Logistic growth, – dN/dt = rN (1 - N/K) N = number, population size r = biotic potential, intrinsic rate of increase. K = carrying capacity – Better represents real populations

12. Logistic model Logistic model works, to a point. – Real organisms have time lags for growth, time to develop eggs, flowers, etc. seasonality, longevity – Real populations may exceed carrying capacity. Easter Island Pribloff Reindeer Kaibab Deer 02 June 2010 12Populations.ppt

13. Easter Island Discovered by Polynesians ~ A.D. 1000 Population grew to several thousand – Used trees for canoes to hunt dolphins – Used wood for cooking – Also ate birds, eggs, vegetables Resources (trees) depleted – No canoes, no dolphins – Warfare over land, food resources Population fell to ~ 100 when discovered by Dutch, Easter Sunday 1722. 02 June 2010 13Populations.ppt

14. 02 June 2010 14Populations.ppt

15. Pribloff reindeer 02 June 2010 15Populations.ppt

16. Logistic model Carrying capacity modeled as a constant. May be variable – Interspecific competition, – Seasonal change, resources abundant in summer, rainy season; resources scarce in winter, dry season – Events may alter resource availability, storms, mild years, human intervention. 02 June 2010 16Populations.ppt

17. Population growth, biotic potential, & life history strategy. 02 June 2010 17Populations.ppt

18. Various species have various strategies for coping with a variable world. 02 June 2010 18Populations.ppt

19. Two general types of Life History Strategies Life History traitr-adapted, Opportunistic K-adapted, Equilibrium OffspringMany, small (high r)Fewer, large (low r) Offspring survivalLowHigh Parental careRareCommon Reproductive ageEarlyLater Reprod. seasons1-fewMany HabitatUnstable, temporaryStable, permanent CompetitivenessLowHigh Population regulationDensity independentDensity dependent Population fluctuationIrruptiveStable near K

20. Life History Strategies Survivorship curves of Opportunistic and Equilibrium species – Opportunistic have Type III – Equilibrium have Type I 02 June 201020Populations.ppt

21. Life History Strategies Fluctuating populations of two interacting populations – Based on pelts sold by Canadian trappers to the Hudson Bay Company, ~1840-1940. 02 June 201021Populations.ppt