unit 6

• Population ecology


  Deals with the number of individuals of a particular species that are found in an area and how and why those numbers change or remain fixed over time
• Population density


  The number of individuals in a population per unit of habitat area
• Population size


  The number of individuals making up a population
• Factors that change population size

  • Births
  • Deaths
  • Immigration
  • Emigration
• Birth rate (b)


  The number of births per 1,000 individuals in a population in a given year
• Death rate (d)


  The number of deaths per 1,000 individuals in a population in a given year
• Growth rate (r)


  The birth rate (b) - the death rate (d)
• Immigration


  The movement of individuals into a population, resulting in an increase in the size of the population
• Emigration


  The movement of individuals out of a population, resulting in a decrease in the population size
• Total fertility rate


  The average number of children born per woman in a population if all women lived to the end of their childbearing years and bore children according to a given fertility rate at each age
• A rate of two children per woman would be the replacement rate for a population if there were no mortality in the female population until the end of their childbearing years
• The replacement fertility rate is 2.1 births per woman in industrialised countries and between 2.5 and 3.3 for developing countries because of higher mortality rates
• Jamaica's total fertility rate is 2.34 births per woman
• Biotic potential


  The maximum rate at which a population could increase under ideal conditions
• Exponential growth


  A J-shaped curve when plotted against time, cannot continue indefinitely
• Environmental resistance


  The limits on population growth set by the environment
• Carrying capacity (k)


  The largest population that can be maintained for an indefinite period of time by a particular environment
• Sigmoid growth curve


  The typical S-shaped population growth curve
• Density dependent factors


  • Competition for resources
  • Predation
  • Parasitism
  • Diseases
• Density independent factors


  • Floods
  • Hurricanes
  • Severe drought
  • Fires
  • Temperature
• Overpopulation


  A situation where the demand on resources by a population exceeds the carrying capacity of an area, resulting in damage to the environment and considered environmentally unsustainable
• Types of overpopulation


  • People overpopulation
  • Consumption overpopulation
• The human population has been increasing exponentially since 1800, as seen by its characteristic J-shaped growth curve
• The world population was 5.77B in 1996, an increase of 69M from 1995 to 1996
• The world population passed the 7 billion mark in 2011 and is expected to pass the 8 billion mark in the next twelve years
• The increase in population numbers is mainly due to a decrease in the death rate
• The main unknown factor in predicting the human population size is the Earth's carrying capacity
• Ways to control population growth

  • Controlling migration
  • Reducing births
  • Reducing births through family planning
  • Using economic rewards and penalties to reduce births
  • Reducing births by empowering women
• Only a few countries, chiefly Canada, Australia and the United States allow large annual increases in population from immigration, and some countries encourage emigration to reduce population pressures
• Lowering the birth rate is the focus of most efforts to slow population growth, as raising the death rate is not ethically acceptable
• Family planning


  Educational and clinical services that help couples choose how many children to have and when to have them, saving society money by reducing the need for various social services
• Providing access to family planning throughout the world would bring about a sharp drop in the estimated 50 million abortions per year
• Most couples in Less Developed Countries (LDCs) want three or four children, which is well above the replacement level required to bring about eventual population stabilisation
• About 20 countries offer small payments to individuals who agree to use contraceptives or be sterilised, but such payments are most likely to attract people who already have all the children they want
• Some countries including China, penalise couples who have more than one or two children by raising their taxes, charging other fees, or not allowing income tax deductions for a couple's third child
• Women tend to have fewer, healthier children and live longer when they have access to education, paying jobs outside the home, and when they live in societies in which their individual rights are not suppressed
• Women do almost all the world's domestic work and child care activities, provide more health care than the entire world's organised health services combined, and do more than half the work associated with growing food, gathering fuel-wood and hauling water, yet they receive only one-tenth of the world's income and own a mere 0.01% of the world's property
• Urbanisation

  The increasing convergence of populations in cities, which seems to be a factor in decreasing fertility rates
• In 1980, nearly one in three persons was an urban dweller, and in 2010 50.6% of the world's population lived in urban centres, a figure expected to rise to 70% by 2050
• The increase in the population of urban areas is attributable more to immigration than to natural increases in the population