Learning Target: Population Density & DistributionCh. 14.3 (pp. 436 – 439)

I Can…Explain how population density, dispersion patterns and survivorship curves, 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 and interspecies

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 is28 turkeys = 7 turkeys / acre2 or 7 turkeys 4 acres2 per square-acre

NOTE: the unit is squared NOT 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 curveReproductive 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.

Put it together.

Think… how do survivorship curves, energy requirements and reproductive strategies are related?

Think… what affect does the habitat and condition of the ecosystem have on reproductive strategies?