Population Pressures : Glossary

There are 74 documents in this section.

  • Replacement-Level Fertility

    29 August 2000

    The level of fertility at which a couple has only enough children to replace themselves, or about two children per couple.

  • Reproductive Health

    29 August 2000

    Reproductive health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity, in all matters relating to the reproductive system and to its functions and processes.

  • Sex Ratio

    29 August 2000

    The number of males per 100 females in a population.

  • Sexually Transmitted Infections (STIs)

    29 August 2000

    Any infection transmitted by sexual intercourse. The most common STIs are gonorrhoea, chlamydia, herpes and AIDS.

  • Total Fertility Rate (TFR)

    29 August 2000

    The average number of children that would be born alive to a woman (or group of women) during her lifetime if she were to pass through her childbearing years conforming to the age-specific fertility rates of a given year. This rate is sometimes stated as the number of children women are having today.

  • Environmental pollution

    22 August 2000

    The contamination of the physical and biological components of the earth/atmosphere system to such an extent that normal environmental processes are adversely affected.

  • Global warming

    22 August 2000

    The idea that increased greenhouse gases cause the Earth's temperature to rise globally.

  • Greenhouse effect

    22 August 2000

    The cause of global warming. Incoming solar radiation is transmitted by the atmosphere to the Earth's surface, which it warms. The energy is retransmitted as thermal radiation, but some of it is absorbed by molecules of greenhouse gases instead of being retransmitted out to space, causing the temperature of the atmosphere to rise. The name comes from the ability of greenhouse glass to transmit incoming solar radiation but retain some of the outgoing thermal radiation to warm the interior of the greenhouse. The 'natural' greenhouse effect is due to the greenhouse gases present for natural reasons, and is also observed for the neighbouring planets in the solar system. The 'enhanced' greenhouse effect is the added effect caused by the greenhouse gases present in the atmosphere due to human activities, such as burning of fossil fuels and deforestation.

  • Greenhouse gases

    22 August 2000

    Molecules in the Earth's atmosphere such a carbon dioxide (CO2), methane (CH4) and CFCs which warm the atmosphere because they absorb some of the thermal radiation emitted from the earth's surface.

  • Ozone hole

    22 August 2000

    A region of the atmosphere over Antarctica where, during spring in the southern hemisphere, about half the atmospheric ozone disappears. The Ozone layer protects the earth's surface from the effects of excess ultraviolet radiation. However, the growth in the volume and use of ozone-destroying chemicals, such as CFCs, has depleted the layer, allowing greater amounts of ultraviolet radiation to pass through to the earth's surface, raising fears of the increased occurrence of skin cancer, eye damage and genetic mutation in terrestrial organisms. (Recently scientists have decreases of 10-20 per cent in ozone over the Arctic).