Population Ecology

Population Dynamics Population: All the individuals of a species that live together in an area Demography: The statistical study of populations, allows predictions to be made about how a population will change Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations Size: number of individuals in an area Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations Density: measurement of population per unit area or unit volume Pop. Density = # of individuals ÷ unit of space Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Your class went out to the wetland across the street to conduct a bird count for the local Audubon Society.    You counted 24 pileated woodpeckers living on 72 acres of land. What was the population density of woodpeckers in this wetland area??

Measuring density of populations is a difficult task. We can count individuals; we can estimate population numbers. Fig. 52.1 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Density is the result of a dynamic interplay between processes that add individuals to a population and those that remove individuals from it Births and immigration add individuals to a population. Births Immigration PopuIation size Emigration Deaths Deaths and emigration remove individuals from a population.

Population Dispersion

How Do Populations Grow? Idealized models describe two kinds of population growth: Exponential Growth 2. Logistic Growth

Exponential Growth Curve Figure 35.3A

Logistic Growth Curve

Carrying Capacity Carrying Capacity (k): The maximum population size that can be supported by the available resources There can only be as many organisms as the environmental resources can support Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Limiting factor Are those elements that prevent a population from attaining its biotic potential. Limiting factors are characterized into density-dependent and density-independent factors.

Population Change and Population Density In density-independent populations Birth rate and death rate do not change with population density In density-dependent populations Birth rates fall and death rates rise with population density

Examples??

Density-dependent Factors are those agents whose limiting effect become more intense as the population density increases. This is a type of negative feedback. Examples? Transmission rates of parasitism and disease Competition for resources (food, space, water, light etc.) Toxic effects of waste products. Increased rates of predation

The Human Population US Census- POP Clock Doubled three times in the last three centuries About 7.4 billion and may reach 9.3 billion by the year 2050 Improved health and technology have lowered death rates

Human Population Growth J curve growth Grows at a rate of about 80 million yearly r =1.3% Why doesn’t environmental resistance take effect? Altering their environment Technological advances The cultural revolution The agricultural revolution The industrial-medical revolution

Age structure Is commonly represented in pyramids Figure 52.25 Rapid growth Afghanistan Slow growth United States Decrease Italy Male Female Age 8 6 4 2 Percent of population 80–84 85 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 20–24 25–29 10–14 5–9 0–4 15–19

History of the Human Population