Tag: human influences on the environment

Lichens represent the symbiotic association between the species of Algae and Fungi. These forms absorb much of their mineral nutrients from the air rather than the soil. So, any contamination would threaten their existence. If air is polluted with sulphur dioxide, then lichens will die in that particular environment. Since the era of industrialization, many species of lichens have gone extinct. Due to this property, lichens are considered to be the indicators of the air pollution. Hence, the correct answer is Usnea (Lichen)'

Lichens are the symbiotic associations between the algae and fungi. These absorb the mineral nutrients from the moisture-laden air instead of the soil. So, any contamination in the air is going to severely affect their growth. The oxides of sulphur have more adverse on the growth of lichens, These disappear from the area when sulphides are in excess in the air. So, these act as bioindicators to the air pollution caused by the sulphur oxides.

Insecta plecoptera (stonefly) is a sensitive insect that produces larvae in the water while the adults live on the land. The stonefly larvae are the indicators to the water pollution caused by the increase in the biological oxygen demand and the rise in temperature. Whenever there is an increase in the organic mass, the dissolved oxygen will decrease and the high rate of respiration of the algal bloom would also increase the temperature. Both these conditions are intolerable by the stonefly larvae and they die quickly. They need a high concentration of dissolved oxygen and normal temperature to survive.

The plants that are used as the indicators to the pollutants are very sensitive to the pollutants such that they either develop disease symptoms or cease to grow when these specific pollutants are present in the air, water or soil. For example, Salvia and Pinus are sensitive to ozone and sulphur dioxide pollution and they show red spots and curling of the leaves. Petunia and Chrysanthemum are sensitive to the peroxy-acetyl nitrate and they show the destruction of the chlorophyll. Lichens fail to grow in the sulphur dioxide pollution.

Stoneflies are the aquatic insects that also live on land as adults. These lay their eggs in water and the larvae hatch in the water itself. These larvae are highly sensitive to water pollution as they need a high concentration of dissolved oxygen to respire. They also show sensitivity to the temperature and as the temperature rises, they begin to die. So, when the water is polluted and has low dissolved oxygen and high temperature due to decomposition, the stoneflies will not be seen. Similarly, overgrowth of sewage fungi and sludge worms in the water body indicates a high concentration of organic pollution. Bloodworms are the endoparasite in the human body. 

Lichens are the most suitable bio-indicators for air pollution, especially sulfur dioxide pollution since they derive their water and essential nutrients mainly from the atmosphere rather than from the soil.  If the air is clean, shrubby, hairy and leafy lichens become abundant. A few lichen species can tolerate quite high levels of pollution and are commonly found on pavements, walls and tree bark in urban areas. The most sensitive lichens are shrubby and leafy while the most tolerant lichens are all crusty in appearance.

Escherechia coli is present in the intestines and is released with the faecal matter. Their presence in the water is indicative of the sewage mixup in the water source.

A. Hardness of water is indicated by the mineral ions concentration.

B. Industrial pollution is indicated by the presence of heavy metals, toxins etc.

C. Escherechia coli presence indicates sewage pollution in water.

D. Chlorine is added for the treatment or purification of water.

Hence, the correct answer is 'Sewage Pollution'.