Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 51 Introduction to Ecology: Population Ecology Copyright © 2005 Brooks/Cole

Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 51 Introduction to Ecology: Population Ecology


Biology, Seventh Edition Solomon • Berg • Martin

Population Ecology



Population DensityNumber of individuals of a species per unit at a given time

Population dispersion (spacing)• Clumped dispersion• Uniform dispersion• Random dispersion



Dispersion of individuals with a

population



Dispersion in a sand pine population in Florida



Four factors that produce changes in population size:

1. Natality: Birth Rate2. Mortality: Death Rate3. Immigration: Entering a territory4. Emigration: Leaving a territory



Carrying capacity (K) is the largest population that can be maintained

–Exponential population growth (J-shaped curve)

–Logistic population curve (S-shaped curve)



Exponential population growth



Carrying capacity and population growth



Density-dependent factors:• Factors that regulate population

growth by affecting a large proportion of the population as population rises

• Examples include predation, disease, and competition



Density-dependent factors and negative feedback



Density-independent factors:• Factors that limit population growth

but are not influenced by changes in population density

• Examples include hurricanes, blizzards, floods, volcanic eruptions, drought, etc



Human Population Growth• World population reached 6.3 billion

in 2003. Today is almost 7.0 billion• Per capita growth rate has declined

from peak in 1965 of about 2% per year to 1.3%

• Scientists predict zero population growth by the end of the 21st century



Human population growth



Population characteristics• Highly developed countries

–Low birth rate, low infant mortality, low fertility rate, long life expectancies, and high GPP

• Developing countries–High birth rate, high infant mortality,

high fertility rate, short life expectancies, and low GNI PPP



Comparison of 2003 population data in developed and developing countries



Birth and death rates in Mexico, 1900–2000



• Age structure influences dynamics• Young age structure causes a

positive population growth momentum as large pre-reproductive age group matures



Age structure diagramsAge structure diagrams



• Developing countries tend to have over-population which degrades the environment. (Mexico, Brazil, India, China etc)

• Developed countries tend to have over-consumption which degrades the environment. (USA, Germany, France, Britain, etc)

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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 51 Introduction to Ecology: Population Ecology Copyright © 2005 Brooks/Cole