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POPULATIONS & CARRYING CAPACITY

POPULATIONS & CARRYING CAPACITY. Population: all the individuals of a species that live together in an area Demography: the statistical study of populations, make predictions about how a population will change. Three Key Characteristics of Populations. Size, number of individuals (N)

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POPULATIONS & CARRYING CAPACITY

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  1. POPULATIONS & CARRYING CAPACITY Populations.ppt

  2. Population: all the individuals of a species that live together in an area • Demography: the statistical study of populations, make predictions about how a population will change Populations.ppt

  3. Three Key Characteristics of Populations • Size, number of individuals (N) • Density (N/ area) • Dispersion, • Random, uniform, clumped, • (appropriate scale) Populations.ppt

  4. Three Key Characteristics of Populations • 1. Size: number of individuals in an area • Characterized by (N) Growth Rate: Birth Rate (natality) - Death Rate (mortality) (How many individuals are born vs. how many die) Populations.ppt

  5. Three Key Characteristics of Populations • 2. Density: measurement of population per unit area or unit volume Pop. Density = # of individuals ÷ unit of space Populations.ppt

  6. 4 Factors that affect density 1. Immigration- movement of individuals into a population 2. Emigration- movement of individuals out of a population Populations.ppt

  7. 4 Factors that affect density 3. Density-dependent factors-Biotic factors in the environment that have an increasing effect as population size increases Ex. disease competition parasites 4. Density-independent factors-Abiotic factors in the environment that affect populations regardless of their density Ex. temperature storms habitat destruction drought Populations.ppt

  8. Three Key Characteristics of Populations • Dispersion: describes their spacing relative to each other Populations.ppt

  9. Dynamic characteristics of populations • Age distribution, • proportions of young, middle-aged, old • Differs in growing, stable, decreasing populations Populations.ppt

  10. Factors That Affect Future Population Growth Immigration + + - Population Mortality Natality - Emigration

  11. 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 Populations.ppt

  12. 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.) Populations.ppt

  13. Other factors that affect population growth Limiting factor-any biotic or abiotic factor that restricts the existence of organisms in a specific environment. • EX.- Amount of water Amount of food Temperature Populations.ppt

  14. Other factors that affect population growth • Carrying Capacity-the maximum population size that can be supported by the available resources • There can only be as many organisms as the environmental resources can support Populations.ppt

  15. Nu m b e r J-shaped curve (exponential growth) Carrying Capacity Carrying Capacity (k) S-shaped curve (logistic growth) Time

  16. Populations.ppt

  17. 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 Populations.ppt

  18. 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. Populations.ppt

  19. 2 Life History Patterns • 1. “R” Strategists • short life span • small body size • reproduce quickly • have many young • little parental care • Ex: cockroaches, weeds, bacteria

  20. 2 Life History Patterns • 2. “K” Strategists • long life span • large body size • reproduce slowly • have few young • provides parental care • Ex: humans, elephants

  21. Two general types ofLife History Strategies

  22. Life History Strategies • Survivorship curves of Opportunistic and Equilibrium species • Opportunistic have Type III • Equilibrium have Type I Populations.ppt

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

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