Unregulated Population Growth Lecture 10 Fall.11 Outline: Population Growth l x , b x vertical (static) life table horizontal (cohort) life table R0 : net reproductive rate T: mean generation time Geometric Population Growth λ : annual rate of increase Exponential Population Growth population doubling time 1
Key Points of Lecture 9. 1. Populations are groups of reproductive individuals living together in the same area and isolated from other groups 2. The environmental conditions that will enable an individual to maintain critical functions are broader than those that will maintain an individual organism which are broader than those that will support a population of the species. The young are frequently most susceptible to harsher environmental conditions and successful reproduction is the critical element of sustaining a population. 3. Species may be adapted to a subset of available conditions – specialization for specific conditions (heat or cold tolerance) 4. Different measures of population size: a. Total counts for sedentary or large organisms with small population sizes, b. subsamples for large populations using quadrats (sedentary organisms like plants) or capture/ recapture (cryptic or highly mobile animals) techniques. R/C = M/N 5. Mark/ recapture methods assume random catch, equal mortality between marked and unmarked, and marks not lost 6. Dispersion is the spatial pattern of individuals in the population: Clumped is most common and is associated with a resource, microclimate, or a beneficial behavior, Uniform next most common and is associated with a direct and frequently antagonistic interaction among individuals. Random least common and assumes uniformity in the environment and lack of behavioral interactions. 2
Population Growth Lecture 10 How fast does a population grow? Factors which add individuals: births and immigration Factors which subtract individuals: deaths and emigration We will restrict most of our discussion of population growth to closed populations : no immigration or emigration. ..or the rates are so small to be inconsequential! How fast a population will grow depends on the composition of the population. One with a high proportion of females in a reproductive age range will grow more rapidly than one composed mostly of post-reproductive and pre-reproductive individuals. Age structure is important . Will return to this when we discuss humans. Parameters that are important:
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