#pollutants

Applied Ecology

Which pollutants are associated with endocrine disruption?

PCBs and environmental estrogens can disrupt endocrine function. Estrogens directly activate estrogen receptors, whereas PCB congeners or their metabolites may mimic hormones, antagonise receptors, or alter hormone synthesis, transport, and metabolism. The outcomes include changed development, reproduction, sex differentiation, and fertility. Carbon dioxide and methane primarily affect climate, while nitrate and phosphate are chiefly associated with nutrient enrichment rather than this specific toxic mechanism. Community-level consequences can emerge when physiological injury changes survival,

Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology

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Applied Ecology

What group of pollutants has contributed to sex ratio shifts in fish?

Estrogens, including natural hormones and synthetic pharmaceutical analogues, can shift fish sex ratios by altering endocrine signalling during sensitive developmental periods. Exposure may induce vitellogenin in males, create intersex gonads, feminise genetic males, reduce sperm quality, and lower reproductive success. Fertilisers chiefly alter nutrient status, while heavy metals and chlorinated hydrocarbons have other toxic actions, although some compounds in those groups can also disrupt endocrine systems. Aquatic effects depend on chemical form, persistence, solubility, dose, and the capac

Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology

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Applied Ecology

Which pollutant is most responsible for depletion of the ozone layer?

Chlorofluorocarbons are stable in the lower atmosphere and can persist long enough to reach the stratosphere. Ultraviolet radiation there photolyses them, releasing chlorine radicals. A chlorine radical catalytically converts ozone to molecular oxygen and is regenerated, allowing one atom to destroy many ozone molecules. This mechanism produced severe polar ozone depletion and motivated international controls under the Montreal Protocol. At organismal level, respiratory surfaces are especially exposed because large volumes of air contact thin, moist epithelia designed for rapid gas exchange. S

Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology

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Applied Ecology

Which of the following is NOT a criteria air pollutant?

Methane is an important greenhouse gas and a precursor in atmospheric chemistry, but it is not one of the conventional criteria air pollutants regulated through ambient concentration standards. Lead, carbon monoxide, and ground-level ozone are criteria pollutants because widespread exposure and documented health or environmental effects justify routine monitoring and legally defined limits. Sound classification links the source, atmospheric fate, exposure route, and mechanism of toxicity rather than relying only on the pollutant's name. Effective management combines cleaner fuels, emission sta

Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology

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