Ecology:  Theory & Practice Course Lecture Notes Site Map   Week 11: Population Growth Issues

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How Populations Grow Growth & Resources Effects of Crowding Population Growth Curves Growth = change in numbers over time Lag period, preparing for rapid growth Geometric increase (doubling) Deceleration, slowing of growth rate Stablilization with carrying capacity or... Overshoot of carrying capacity J-curves or S-curves (illustrations) Rapid Growth Rates "Population Bomb" of human population More pronounced in developing nations Can result in extreme poverty, malnutrition, and even starvation Usually produces crowding, higher infant mortality, and lowered disease resistance May be linked to insufficient infrastructure Characteristics of Populations Natality Rate (birth rate) - varies according to species, may be affected by extrinsic factors Mortality Rate (death rate) - varies by species, and strongly affected by extrinsic factors Immigration/Emigration Rate - higher in animal populations Calculation of Growth Rates Size of population - measured by Growth Rate (change in numbers over a given time interval Growth Rate = Birth Rate + Immigration - Death Rate - Emigration Rate Growth Rates for human populations are increasing at a slower pace (populations are still growing) Age of Reproductive Activity Younger mothers make population grow faster (illustration) Delay of births slows population growth Three groups in any population (illustration) Pre-Reproductive Reproductive Post-Reproductive Survivorship Curves Based on tracking the number of survivors within a given size population (illustrations) Type I Survivorship = population survives for most of life expectancy (large animals) Type II Survivorship = relatively even death rates during life span (many birds) Type III Survivorship = high infant mortality (insects) Human Population Growth Correlations with population growth Source and type of food supply (illustration) Fossil fuel energy consumed (illustration) Per capita income (illustration) Type and availability of housing Obstacles to Population Control Religious and cultural biases Difficulty in launching education programs Cost and infrastructural limitations Political unrest Commitment for the long term Successes in Population Control South Korean experience Role of women in taking charge of their own reproductive destiny Programs of World Health Organization (WHO) Slowing of population growth in developed nations  
      Key terms we use to describe the effects of toxics

 

Carrying Capacity	J-Curves	S-Curves
Iks	John Calhoun's Rats	Natality Rate
Mortality Rate	Immigration	Emigration
Growth Rates	Pre-Reproductive	Reproductive
Post-Reproductive	Type I, II, III Survivorship	WHO

 

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copyright Gaytha A. Langlois, Ph.D., 1999 Bryant College, Smithfield, RI 02917 E-mail: langlois@bryant.edu Last Updated: April 2005