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C.PopulationSu11 - Population Ecology POPULATION ECOLOGY...

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Population Ecology Heyer 1 POPULATION ECOLOGY Biosphere Ecosystem Community Population Ecology: Interactions among members of the same species in a given habitat. THE REALM OF ECOLOGY Biosphere Ecosystems Communities Populations Organisms • Species – Interbreed – Fertile offspring • Population – Interacting group – Share resources – Geographical range SPECIES and POPULATION 1. Size (N): # of individuals 2. Density: # of individuals per unit area 3. Distribution: dispersal within an area 4. Age structure: proportion in each age category Often gender-specific 5. Growth patterns: changes in population size and/or density over time 6. Life history strategies: cost/benefit in stable vs. unstable environments POPULATION DYNAMICS Factors that Limit Population Size Abiotic (nonliving) Limiting Factors – Temperature – Water Soil type – Sunlight – Salinity Wind stress Altitude, depth Biotic (living) Limiting Factors Food source – Competition – Predators Social factors, mates Pathogens, parasites – Vegetation Factors that Limit Population Size Density Dependent Limiting Factors Limited resources Food Water Safe refuge Predation Competition Living space Disease, Pollution Density Independent Limiting Factors Natural disasters Hurricanes Floods, landslides, volcanoes Drought, frost Environmental insult Deforestation Pesticide Fire Climatic change
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Population Ecology Heyer 2 Density, Dispersal, & Distribution (a) Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory. (b) Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions between neighbors. (c) Random. Dandelions grow from windblown seeds that land at random and later germinate. Figure 52.3 POPULATION AGE STRUCTURE Demography & Life Tables Survivorship Curves Age structure is relative number of individuals of each age. Sex ratio is % of females to males. Study of human populations = demography POPULATION AGE STRUCTURE Vital Statistics of Populations POPULATION AGE STRUCTURE Vital Statistics of Populations Average births per individual = fecundity . Population birth rate = natality. Population death rate = mortality. Generation time = age at first reproduction. Life Tables Created in one of two ways: 1. Follow a cohort . or 2. Snapshot of a population at a specific time point. POPULATION AGE STRUCTURE Cohort Survivorship Curve Number of a cohort surviving to subsequent years
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Population Ecology Heyer 3 POPULATION AGE STRUCTURE Cohort Survivorship Curve Number of a cohort surviving to subsequent years Fig. 53.5 Beldings Ground Squirrels Survivorship Curves • Type I: low juvenile mortality
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