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Learning Target: Population Density & Distribution. Ch. 14.3 (pp. 436 – 439). I Can …E xplain how survivorship curves, population density and dispersion patterns affect the reproductive strategies of a species. I Will … Calculate the density of a population of organisms in a given area.
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Learning Target: Population Density & Distribution Ch. 14.3 (pp. 436 – 439)
I Can…Explain how survivorship curves, population density and dispersion patterns affect the reproductive strategies of a species. • I Will… • Calculate the density of a population of organisms in a given area. • Describe the dispersion pattern of organisms in a given area. • Infer what type of intraspecies relationships cause specific patterns of dispersion. • Describe the three types of survivorship curves. • Infer connections between survivorship curves and reproductive strategies.
KEY CONCEPT: Each population has a density, a dispersion, and a reproductive strategy. Population density – is a measurement of the number of individuals in a defined space. # of individuals = Population density Area (units2) e.g. 28 turkeys in a field of 4-square acres is 28 turkeys = 7 turkeys / acre2 or 7 turkeys per 4 acres2 square-acre NOTE: the unit is squaredNOT the number before the unit
Population dispersion – the way in which individuals of a population are spread in an area or volume. Clumped dispersion – individuals live close together in order to facilitate mating, gain protection, or access food resources.
Uniform dispersion – Territoriality and intraspecies (within species) competition for limited resources leads to individuals living at specific distances from one another.
Random dispersion – Individuals are spread randomly within an area or volume. Species often solitary with few competitors and few natural predators.
Survivorship curve – generalized diagram showing the number of surviving members over time from a measured set of births. Type I – low level of infant mortality (death) and population survives to old age. Common in large mammals and humans.
Survivorship curve Type II – Survivorship rate is equal at all ages of an organism’s life. (Equal chance of living or dying at anytime) Common in birds, small mammals, and reptiles.
Survivorship curve Type III – Very high birthrate and very high infant mortality (death) rate. Common in invertebrates (no backbone), fish, amphibians, and plants
Survivorship curve Reproductive strategy – reproductive practice that provides a survival strategy for a species. e.g. Fish (Type III) lay hundreds of eggs to ensure at least some offspring reach adulthood without being eaten and are able to reproduce.