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Section 14-3 and 14-4 “Population”. Write everything that is underlined. Section 14.3 KEY CONCEPT: Each population has a density, a dispersion, and a reproductive strategy. Populations Population density is a measurement of the number of individuals living in a defined space .
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Section 14-3 and 14-4“Population” Write everything that isunderlined
Section 14.3 KEY CONCEPT: Each population has a density, a dispersion, and a reproductive strategy.
Populations • Population density is a measurement of the number of individuals living in a defined space. • Population dispersion refers to how a population is spread in an area. • There are three types of dispersion illustrated on the next slides:
Type I: low level of infant mortality and an older population • common to large mammals and humans • Type II: survivorship rate is equal at all stages of life • common to birdsand reptiles • Survivorship curves: • Type III: very high birth rate, very high infant mortality • common to invertebrates and plants
Section 14.4 KEY CONCEPT: Populations grow in predictable patterns.
Population Growth • The size of a population is always changing. • Four factors affect the size of a population: • Births • Deaths • Immigration • (Moving into an area) • Emigration • (Moving out of an area)
Exponential growth is a rapid population increase due to an abundance (lots of) of resources.
Logistic growth is due to a population facing limited resources.
Carrying capacity is the maximum number of individuals in a population that the environment can support. • This is due to limited resources (food, shelter, space)
A population crash is a dramatic decline in the size of a population over a short period of time.
A limiting factoris something that keeps the size of a population down. • Limiting factors can depend on the density of individuals in the population or not.
Density-dependentlimiting factors are affected by the number of individuals in a given area. • Predation • Competition • Parasitism and disease
Density-independentlimiting factors limit a population’s growth regardless of the density. • unusual weather • natural disasters • human activities