REFERENCE SECTION: POLLUTION 
The root cause of pollution is Man's unique ability to over-use the 
biosphere's natural resources; 45% is a conservative guesstimate of 
this use by just one species. Although most visible on ingestive 
heterotrophs, particularly vertebrates, it is the effects of pollution 
on autotrophs and saprotrophs that is important; this is because most 
pollutants interfere with food webs by either increasing the natural 
mutation rates or decreasing the reproductive rates of these organisms.
Complete the Table below, which summarizes the sources of the most important pollutants and their biological and/or ecological importance, by inserting the correct name of the pollutant(s) from this list: Acidic oxides (e.g., NO2, SO2, and SO3); Biocides (e.g., Warfarin and DDT); Carbon dioxide; Carbon monoxide; Chlorofluorocarbons (CFCs); Hot water discharges; Lead compounds; Metal ions [e.g., Hg2+(aq) and Cd2+(aq)]; Methane; Nitrogen oxides; Non-biodegradable detergents; Phosphates and nitrates; Radioactive emissions (a- and b-particles and g-rays); Sewage; Unburned hydrocarbons.
Source(s)
 Pollutant(s) 
Biological/Ecological Importance
Vehicle exhausts
Paints
Mine workings
Storage batteries
 
Accumulate up trophic levels.
Inhibit enzymes.
Mine-workings
Industry
 
Accumulate up trophic levels.
Inhibit enzymes.
Nuclear power
stations
 
Cause mutations; i.e., changes in
the sequence of nucleotides in
deoxyribonucleic acid (DNA) or in
ribonucleic acid (RNA).
Refrigerants and
Aerosols
Vehicle and jet
exhausts
Agriculture and
Landfill sites
 
Deplete ozone layer, allowing more
u.v. light to reach biosphere: so
increased mutation rates, as well
as decreased photosynthesis by
marine protoctistans.  Contribute
to 'greenhouse effect'.  *
Fossil fuel power
stations
Vehicle exhausts
'Slash and burn'
agriculture
 
Contributes to 'greenhouse effect'.
May increase plant yields, because
the gas is a limiting factor in
photosynthesis, and (indirectly)
increase the number of insects.
Power stations
 
Denature the enzymes of aquatic 
organisms. Decrease concentrations, 
in aquatic habitats, of dissolved 
gases (e.g., O2, CO2, and N2).
Fossil fuel power
stations
Vehicle exhausts
 
Reacts reversibly but strongly with
haemoglobin, and so reduces
the availability of dioxygen to
aerobically respiring cells.
Households
Factories
 
Cause 'foaming', and so prevents
the diffusion of gases essential to
aquatic organisms.


Source(s)
 Pollutant(s) 
Biological/Ecological Importance
Households
Factories
 
Provides rich source of chemical
energy for pathogens to reproduce.
Cause eutrophication.  #
Agriculture;
NPK fertilizers
 
Cause eutrophication. Contribute to
soil erosion. Nitrates are soluble,
so maybe present in water supply.
Agriculture
Forestry
Human habitats
 
Accumulate up trophic levels. Can
cause mutations. Are not always
selective to pests, which usually
evolve resistance rapidly.  $
Vehicle exhausts 
 
Contribute to photochemical smog,
which destroys various biological
molecules, decreases efficiency of
gas-exchange surfaces in animals,
and increases mutation rates.
Coal-fired power
stations
 
Dissolve in atmospheric water
vapour, which precipitates as 'acid
rain'; the acidic environments
result in the release of toxic ions 
[e.g., aq. Al(III) and Pb(II)], as
well as reduced reproductive rates.
Contribute to photochemical smog.
                                                                   [15]
*  The 'greenhouse effect' is caused by certain gases in the atmosphere 
trapping heat radiated from the Earth. These 'greenhouse' gases absorb 
outgoing infra-red radiation but do not significantly affect incoming 
visible radiation (i.e., they act like panes of glass in a greenhouse); 
the higher their concentration, the more radiation returned and so the 
higher the temperature of the Earth's surfaces. 'Global warming' is the 
gradual increase in temperature of the lower atmosphere, as a result of 
the steady accumulation of greenhouse gases; its effects are expected 
to include rises in sea levels, decreased amounts of moisture in soils, 
milder winters, and disruption of delicately balanced ecosystems. 
#  The consequences of eutrophication, or over-enrichment, of water are 
as follows. Nutrient ions are one of the limiting factors in the growth 
of algae in aquatic habitats: so, these photosynthetic protoctistans 
reproduce rapidly when these ions are in abundance. The phase of rapid 
reproduction is followed by death of the entire population of algae, 
because of the decreased availability of limiting factors (i.e., ions, 
carbon dioxide, or light); the dead algae, which often release toxins, 
are then decomposed by saprotrophic bacteria, whose aerobic activities 
reduce a habitat's dioxygen supply to levels which cannot support other 
aerobic organisms (e.g., crustaceans and fish). 
  The evolution of pest populations resistant to a biocide occurs via 
the mechanism of natural selection, as exemplified by the evolution of 
brown rats (Rattus norvegicus) resistant to Warfarin (a blood-clotting 
toxin). Thus, structural variation has occurred in rat populations due 
to natural mutations, followed by the exchange of genes via meiosis and 
random fertilization. Some of these mutations have resulted in some 
rats containing alleles which code for the catabolism of Warfarin. 
These individuals have been the fittest in environments where the agent 
of selection has been Warfarin, and so more of these have survived to 
reproductive maturity. Their offspring have inherited these favourable 
alleles; and so, within the gene pool of brown rats, the frequency of 
Warfarin-resistant alleles has increased.
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