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DEMOGRAPHY

DEMOGRAPHY. The study of birth and death processes that determine growth and age structure of a population. Each age class of a population has an expected:. Mortality rate. Fecundity rate. Demographic characteristics can be represented in:. Life Tables summarize deaths and/or births

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DEMOGRAPHY

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  1. DEMOGRAPHY The study of birth and death processes that determine growth and age structure of a population.

  2. Each age class of a population has an expected: Mortality rate Fecundity rate

  3. Demographic characteristics can be represented in: • Life Tables • summarize deaths and/or births • in different age classes of a population Conventional life table

  4. Cactus

  5. Demographic characteristics can be represented in: • Life Tables • summarize deaths and/or births • in different age classes of a population Conventional life table Diagrammatic life table (flow diagram)

  6. Diagrammatic Life Table # in each age class Fecundity Probability of survival (Assumes 50-50 sex ratio)

  7. 2) Survivorship Curves 1,000 I 100 II Number of survivors (log scale) 10 III 1 0 50 100 Percentage of maximum life span Fig. 53-6

  8. Imagine that a species of fish used to be a broadcast spawner (producing many eggs that then get no subsequent parental care) but has evolved to be a mouth brooder (holding the eggs in the parent’s mouth until they hatch and then caring for the young for a while). We would expect the survivorship curve of this species to shift A) from Type I to Type II or III. B) from Type II to Type I. C) from Type III to Type I or II. D) from Type II to Type III. E) The survivorship type would vary unpredictably.

  9. POPULATION DENSITY

  10. Births and immigration add individuals to a population. Immigration Births PopuIationsize Emigration Deaths Deaths and emigration remove individuals from a population. Population Dynamics

  11. Population Density (Abundance): # of individuals of the same species that occur in a given area. Knowing the population density of a particular species is important for conservation and management decisions.

  12. White Abalone

  13. Bald Eagles

  14. White-tailed deer

  15. Density Estimation (“Sampling”) Techniques Census (direct counts) Indirect counts Sample plots or transects Mark-recapture

  16. Mark-recapture Technique: • capture and mark several, then release all • soon after, capture more, SOME of which • have marks (“recaptured”)

  17. Reasoning: Proportion of 2nd capture that are recaptured individuals represents the proportionmarked in entire population... R/C = M/N M = # caught and Marked in first trapping session C = # Caught in second trapping session R = # marked individuals Recaptured N = estimated Number in entire population

  18. R/C = M/N So, N = M / (R/C) N = (M x C) / R

  19. Assumptions of mark-recapture technique: • closed population (no immigration or emigration) • no births or deaths (in sampling period) • marked and unmarked individuals • equally likely to be caught in second trapping

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