AUFBAU1 [REFERENCE SECTION: POLLUTION]

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.

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*  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.

Dr. R. Peters                   Next                     Contents' List