BIOLOGY 1.5 Marks Questions

Dobson unit is the simplest unit for measuring ozone concentration. One Dobson unit is the number of ozone molecule required to form a larger of pure ozone 0.01 millimetre thick at 0°C. temperature and one atmospheric pressure Dobson units are mainly used to measure atmospheric ozone level.

Radiation is harmful for living beings, it damages the cells. In high concentration it causes extemly total effects, many radiactive substances reach mumans through the food chains, they get abserbet by plants and ener the food chain.
1. Iodine 131 : Damages thyroid glad especially in children, famages WBCs, bone marrow, causes skin cancer, infertility etc.
2. Strontium - 90 : Reaches human through the use of containinated food, meat, milk, bacry products through vegetation and its use in animals. If maximum strontium gets concentrated in bones, it causes bone cancer and tissue degeneration.
3. Cesium-137 : Causes neural, muscular and genetic changes.
4. Uranium : Causes skin cancer, tumors.
5. Radon 222 : Causes leukemia, mast tumor and kidney cancer.

(a) Carbon dioxide, methane, oxides of nitrogen and cholorofloro carbon.
(b) Hole in the ozone layer is caused by cholorofloro carbon (CFC). CFC decomposes in absence of Ultraviolet radiation, resulting in the release of chlorine atoms. These function as catalysts in ozone layer depletion and further release molecular oxygen. Hence, chlorine does not take part in reaction but effect ozone layer continuously.

Biochemical Oxygen Demand (B.O.D.) : Biochemical oxygen demand (B.O.D.) represents the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter under aerobic (Oxygen is present) conditions at a specified temperature. The presence of a sufficient concentrationof dissolved oxygen is critical to maintain the aquatic life and aesthetic quality of streams and lakes. Determining how organic matter affects the concentration of dissolved oxygen (DO) in a stream or lake is integral to water- quality management. The decay of organic matter in water is measured as biochemical or chemical oxygen demand. Oxygen demand is a measure of the amount of oxidizable substances in a water sample that can lower DO concentrations.

(a) Catalytic Converter : Catalytic converter are fitted into automobiles for reducing emission of poisonous gases. They have expensive metals, platinum palladium and rhodium as the catalysts. As the exhaust passes through the catalytic converter, unburnt hydrocarbons are converted into carbon dioxide (CO₂) and water and carbon monoxide (CO) and nitric oxide are changed into carbon dioxide and nitrogen gas, respectively. However, automobiles equipped with catalytic converter should always use unleaded petrol because lead present in petrol, inactivates the catalyst.
(b) Ultraviolet-B : Ultraviolet B (UV-B) radiations are of larger wavelength and cannot be absorbed by Earth's atmosphere. These rays are highly injurious to living organisms. They damage DNA and may cause mutation. It causes aging of skin, damage to skin cells and various types of skin cancers. UV-B are very dangerous for human eyes because cornea of human eye absorbs UV-B radiation, and a high dose of UV-B causes inflammation of cornea, called snow-blindness cataract, etc. or may permanently damage it.

(a) Radioactive wastes : The use of nuclear energy generate radioactive wastes. Radiation, given off by radioactive waste is extremely damaging to biological organisms, because it causes mutations to occur at a very high rate. At lower doses, nuclear radiation creates various disorders, especially cancer and at higher doses, it is lethal. Hence radioactive waste has to be dealt with utmost caution because it is an extremely potent pollutants. The storage of radioactive waste, after sufficient pre-treatment, should be done in suitable shielded containers buried within the rocks about 500m deep below the earth's surface. However, this method of disposal is not agreeable to many people.
(b) Defunct ships and e-wastes : Defunt ships refers to those articles which are no longer operating or dead. Irreparable computers and other electronic goods are known as electronic wastes (e-wastes). E-wastes are buried in landfills or incinerated. Developing countries like China, India and Pakistan recover metals like copper, iron, silicon, nickel and gold through recycling from e-wastes which are imported from developed countries. Unlike developed countries, which have specifically built facilities for recycling of e-wastes, recycling in developing countries often involves manual participation thus exposing workers to toxic substances present in e-wastes. Thus, e-wastes should be treated through environment- friendly manner.
(c) Municipal solid wastes : Municipal solid wastes are wastes from homes, offices, schools, stores, hospitals, etc; that are collected and disposed by the municipality. It mainly comprises of paper, glass, plastic, rubber, metals, food wastes, textile, etc. Burning reduces the volume of these wastes although it is generally not burnt to completion and open landfill often serve as the breeding ground for flies and rats.

Measures to reduce environmental pollution :
(i) Plant more and more trees in an available space. (ii) Use recycleable materials. (iii) Prefer walk or use of public transport instead of private vehicle. (iv) Use paper bags or cloth bags instead of polythene bags. (v) Conserve water by not misusing it and use less water for drainage. (vi) Always throwing waste paper and other garbage in dustbins. (vii) Keep the volume of T.V. and music system low. (viii) Seal all the leaking taps at home. (ix) Never throw garbage in drains. (x) Prefer to use wooden items like wooden pencils, wooden pencil boxes, etc. than plastic items like plastic pencils, etc.

At the poles, (over Antarctica) the winds blow in a circular pattern and create polar vortices. Water droplets present in the atmosphere form ice crystals inside these vortices. CFCs get collected on the surfaces of these ice crystals and destroy the ozone. This has resulted information of a large area of thinned ozone layer, commonly called as the ozone hole over Antarctica.
Excessive UV exposure increases risk of various skin cancers, cataracts and other eye diseases, as well as accelerated skin ageing. It may also adversely affect people's ability to resist infectious diseases. High doses of UV-B causes inflammation of cornea, called snow blindness cataract, etc. Such exposure may permanently damage the cornea.

Significance of Ozone Layer : Ozone protects the Earth from harmful ultraviolet (UV) rays from the Sun. Without the Ozone layer in the atmosphere, life on Earth would be very difficult. Plants cannot live and grow in heavy ultraviolet radiation, nor can the planktons that serve as food for most of the ocean life. With a weakening of the Ozone Layer shield, humans would be more susceptible to skin cancer, cataracts and impaired inmmune systems.
Ozone depletion substances : Production of chlorine-containing chemicals, such as chlorofluorocarbons (CFCs), has added to depletion of the Ozone Layer.
Chemicals containing chlorine and bromine atoms are released in the atmosphere through human activities. These chemicals combine with certain weather conditions to cause reactions in the Ozone Layer, leading to ozone molecules getting destroyed.
Effects of Stratospheric ozone depletion : Ozone layer depletion causes increased UV radiation levels at the Earth’s surface, which is damaging to human health. Negative effects include increases in certain types of skin cancers, eye cataracts and immune deficiency disorders.

Eutrophication is the natural ageing of the water source due to biochemical wastes. When nitrates and phosphates increase in water body in high quantity, algae and other plants grow rapidly. It results in the algal bloom. The water turns odorous, dark, and translucent, with lack of dissolved oxygen. It results in the death of fishes and other animals.

Ahmed Khan has been producing plastic waste sacks for 20 years. About 8 years ago, he realised that plastic waste was a real problem therefore, he and his company developed a fine powder of recycled modified plastic known as polyblend. In collaboration with R.V. College of Engineering and the Bangalore City Corporation, Ahmed Khan proved that the presence of Polyblend in bitumen (used to lay roads), enhances bitumen's water repellant properties, and helped to increase road life by a factor of three. Using Khan's technique, by the year 2002, more than 40kms of road in Bangalore has already been laid by the blend of Polyblend and bitumen. Hence, by the innovation of polyblend, we might avoid being smoothered by plastic waste.

Effects of acid rain:
(i) Due to acid rain and acid deposition, historical monuments like, Tajmahal, Statue of Liberty, etc. are badly affected.
(ii) Acid rain kills beneficial microbes present in soil resulting in the imbalance of terrestrial ecosystem.
(iii) In aquatic ecosystem acid rain kills planktons, mollusks, fishes, at pH below 5. It results in the imbalance of aquatic ecosystem.