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19 Cards in this Set
- Front
- Back
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Population |
Group of organisms of the same species occupying a particular space at the same time - both genetic and ecological units in which species members interact with one another |
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Metapopulation |
Spatially separated, disjunction population which is distributed in patches across a heterogeneous landscape and interconnected by immigration (dispersal) |
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Dispersal |
Often from a source to a sink - empty habitat filled by immigration |
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How are populations measured? Properties of populations |
Density, dispersion, sex ratios, age structure, mortality, natality |
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Measuring populations: population density |
# individuals in a given area or volume, # organisms occupying defined unit of space - count all the individuals in a population - estimate by sampling - mark-recapture method depends on likelihood of recapturing the same individual - crude density: # of individuals per unit area - ecological density: measured in terms of useable habitat, hard to determine what portion of a habitat represents living space |
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Problems with measuring density |
Nothing about how populations are distributed over space and time |
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Patterns of dispersion |
Uniform, random and clumped - strongly influenced by patterns of landscape and interactions among members of population |
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Uniform or regular dispersion |
Spacing of individuals is more even than would occur by chance - can result from intraspecific competition among members of a population - wolf packs are uniform |
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Random dispersion pattern |
Position of each individual: independent of others or if the occupation of each spot is equally likely - Rare and only occur where: environment is uniform, resources equally available throughout year, interaction among members of population produce no patterns of attraction or avoidance |
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Clumped, clustered, contagious or aggregated dispersion pattern |
- most common pattern - result of responses by organisms to: habitat differences, daily and seasonal environmental changes, reproductive patterns and social behavior - reasons for clumped distributions include: poor dispersal capability of the young, patchy distribution of resources, social organization |
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Sex Ratio |
Proportion males to females 1:1 in most sexually reproducing organisms - primary sex ratio: the ratio at conception - secondary sex ratio: the ratio at birth --- among animals: often weighted towards males but as age class increases there is a ratio shift towards females |
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Exponential growth model |
- uncontrolled growth - applicable only to initial growth after colonization of an unexploited habitat: transient phenomenon - not biological realistic or sustainable |
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Logistic growth model |
- growth is slowed by population-limiting factors - k = carrying capacity; maximum population size that an environment can support |
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Extinction of species |
Natural process (accelerated by humans; 75% of modern extinctions are anthropogenic) - extinction usually a result of an accumulation of local population extinctions - extinction of a local population = extirpatioin - small isolated populations endemic to specific habitats are more vulnerable to extirpation and extinction |
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Intraspecific poplation ecology |
Density dependence is implicit in the concept of population regulation - density-dependent effects influence the population in proportion to its size - density dependent mechanisms act largely though shortages and competition for resources |
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Density Independent Factors |
# of organisms: determined by an interaction between density-dependent and density independent influences - may vary among and within populations |
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Life Histories |
Series of events from birth, reproduction, death Include: - age at first reproduction - frequency of reproduction - number of offspring - amount of parental care given - energy cost of reproduction Influences by density-dependency and density independent factors |
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Interspecific interactions: +/+ +/- +/0 0/0 -/0 -/- |
Mutualism, predator/prey, commensalism, no interaction, amensalism, competition |
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Control of community structure |
Keystone species, top-down or bottom-up |
