some of it is scannted and some typed.. sorry for the inconvenience .. pls cooperate

biology 

ENVIRONMENT: The physical and the biological world which forms immediate surroundings of an organism.

Environment consists of three constituents/components

(a)   Biotic components i.e. Living organisms (plants, animals and micro-organisms)

(b)   Abiotic components i.e. Non-living constituents (land, air and water)  

(c)    Meteorological components i.e. Climatic factors (rainfall, humidity, sunlight, temperature etc).

Environmental problems:  Due to growing population there is depletion of resources and increased level of environmental pollution.

Pollution: Any change in physical, chemical or biological characteristic of air, land and water is called pollution. The agents which bring about these changes are called pollutants.

Pollutants are divided into two categories:

I)           Biodegradable pollutants and

II)         Non- biodegradable pollutants

Biodegradable pollutants: Those pollutants which can be degraded or broken down into simple harmless form by the action of micro-organisms like bacteria and fungi E.g. Household garbage, urine, faecal matter, agricultural residue, cattle dung, wood, paper cloth, leather, wool, silk, bones, hair, nails etc.

Harmful effects of biodegradable wastes:

(1)       They act as pollutants only when  their quantity  is large and they accumulate,

(2)       Decomposition of Biodegradable wastes results in spread of foul smell in the environment.

(3)       Their accumulation results in spread of vectors such as mosquitoes and flies which are carriers of pathogens and transmit diseases.

(4)       Biodegradable wastes block drains and result in water logging which becomes the breeding ground for disease spreading mosquitoes.

(5)        Certain industrial wastes which are biodegradable, when dumped on the ground result in loss of fertility of the soil.

However, recycling of biodegradable wastes helps to return the nutrients back to the environment and thus helps in maintaining ecological balance.

Non biological pollutants: Those pollutants which cannot be broken down into simple harmless form by the action of micro-organisms. Eg. plastic, Glass, pesticides like D.D.T, heavy metals like arsenic and lead, aluminum foil, silver foil, iron nails, radioactive substances, industrial wastes, polythene, nylon etc.

Harmful effects of non-biodegradable wastes:

(1)       Non- biodegradable wastes such as fertilizers, pesticides, industrial wastes when dumped on the ground   reduce soil fertility and, therefore, reduce crop yield.

(2)       Non-biodegradable wastes cause bio-magnification

Act. 15., Act. 15.2 Act. 15.4

Bio- magnification: it is the progressive increase in the concentration of non-biodegradable chemicals in the bodies of living organisms from one trophic level to another along the food chain. Since humans occupy top level in the food chain the concentration of these harmful chemicals is the highest in their body. As a result of bio-magnification different amounts of non-biodegradable pesticides are present in our food grains, vegetables, milk and milk products, eggs. Accumulation of Hg in our body leads to disease Minamata and accumulation of fluorine leads to fluorosis and bending of legs.

Recycling of non-biodegradable wastes reduces pollution.

ECOSYSTEM AND ITS COMPONENTS: Dynamic self-sustaining system of interactions between the biotic and the abiotic factors. It is the structural and functional unit of biosphere. Biotic components can also be classified as autotrophs or producers and hetrotrophs or consumers. 

Autotrophs or Producers: Those organisms which produce food by photosynthesis i.e. Organisms which can make organic compounds like sugar and starch from inorganic substances using the radiant energy of the sun in the presence of chlorophyll. For example all green plants blue green algae and some bacteria.

Heterotrophs or consumers: Those organisms which cannot prepare their food from simple inorganic raw materials but depend upon the producers for food either directly or indirectly by feeding on other consumers. They can be further classified into herbivores, carnivores, omnivores, decomposers and parasites.

Herbivores: are the animals that eat vegetation or plants e.g. cows, horse grasshopper, deer, rabbit etc.

Carnivores: are those animals that eat meat or flesh of other animals, e.g. tigers, lions, wolves etc.

Omnivores: are those animals that eat both plants and animals e.g. humans crows, cockroaches,

Parasites: are those organisms that live on (ectoparasites) or inside (endoparasites) the body of other organisms, e.g. fleas, lice, mosquitoes, tapeworm, Liver fluke etc.

Decomposers: Those organisms that breakdown the complex organic substances into simple inorganic substances and thus obtain energy. E.g. many bacteria and fungi

Act. 15.3

Role of decomposers in the biosphere:

i)            They help in recycling of nutrients

ii)          They clean up the environment and make it free of dead bodies

TYPES OF ECOSYSTEM:

(a)   Natural ecosystem: These operate in nature by themselves without any human interference. Eg Thar Desert, rivers, lakes, ocean etc.

(b)   Man-made or artificial ecosystems: These are created and maintained by humans. E.g. Aquarium, crop field, orchard, parks etc.

Ecosystems can also be classified as:

(a)  Aquatic ecosystems: In these ecosystems all the interacting organisms are present in water. E.g. marine and freshwater ecosystems such as oceans, seas, ponds, lakes.

( Marine ecosystem is one of the largest and most uniform ecosystem)

      (b)          Terrestrial ecosystems: In these ecosystems all the interacting organisms are present on land. E.g. desert, forest, grassland ecosystems.

FOOD CHAIN: It is the interaction among various organisms involving flow of energy in the form of food from one tropic level to the next in the biosphere. It is the unidirectional flow of energy in the biosphere. Thus, it is a series of organisms taking part at various biotic levels. It starts from the producer and ends in consumer. The ultimate source of energy is the sun.

Effect of human activities on the environment;

 Changes in the environment affects us and our activities change the environment around us. There exists a great inter relationship between man and environment where both influence each other. When the environment is polluted beyond the capacity of cleaning agents of nature, ecological balance is lost and the environment becomes polluted.

OZONE LAYER: Ozone (O₃) is an isotope of oxygen, i.e. it is formed by three atoms of oxygen. it exists in the higher levels of atmosphere( the stratosphere). The higher energy U.V radiations from the sun split oxygen molecule into atomic oxygen which then combine with molecular oxygen to form ozone.  

  U. V

O2                            O     +        O

O       +        O2                        O3       

 Importance of ozone;

Ozone at higher levels shields the surface of earth from U.V radiations of the sun and prevent them from passing through it. It absorbs most of these harmful radiations.

Harmful effects of U.V radiations:

(1)       Exposure to high levels of U.V radiations weaken the human immune system and cause skin cancer, cataract of the eye, genetic defects.

(2)       U.V radiations affect plant growth and productivity.

(3)       Phytoplanktons and other microscopic marine plants are harmed by U.V radiations and their numbers decline resulting in disruption of the entire marine ecosystem.

(4)        It may cause global rainfall, leading to ecological disturbances and reduction in global food supplies.

(5)       Exposure to U.V radiations accelerates the deterioration of plastic,wood ,paper, cotton and wool.

 Depletion of ozone layer:

(1)       Synthetic chemicals such as chlorofluorocarbons (CFC’s) which are used as refrigerants and in fire extinguishers. When they are released into the air they accumulate in the upper atmosphere and react with ozone and result in its reduction and creation of ozone holes.

(2)       Natural sources like chlorine molecules which are being released into the atmosphere delete the ozone layer.

(3)       Volcanic eruptions contribute to about 5% damage to the ozone layer because chemicals like HCI, sulphur–dioxide are released during volcanic eruptions and they also damage the ozone layer.

In 1987, the United Nations Environment Programme (UNEP) has banned the use of CFC containing compounds.

(1)       This involves to limit the use of ozone depleting chemicals

(2)       Phasing out the ozone depleting chemicals

MANAGEMENT OF GARBAGE WE PRODUCE:  Wastes generated by commercial and domestic activities are often indiscriminately disposed. Unscientific management of such waste leads to serious environmental problems which are acute in cities and towns.

Methods being adopted for disposal of solid waste are a serious health concern. Particularly during rainy season, runoff water and high humid conditions increase the health hazards. The land filled sites which are not well maintained are prone to cause ground water contamination. Open dumping of garbage serves as breeding ground for disease causing vectors such as houseflies, mosquitoes, rats and other pests. Diseases like typhoid, dysentery, yellow fever, dengue fever, cholera etc. spread.

Three major steps involved in garbage management are:

(1)       Collection of garbage

(2)       Transportation of garbage

(3)       Disposal of garbage

Collection of garbage is done from residential areas and the practices differ from city to city. Each city has its own collection centre.  Wastes are collected in smaller bins and are then transported to larger bins.

Disposal of garbage in a well managed lab. Adopting scientific methods is termed as sanitary land fill. This involves identifying a suitable site. Land filling is a slow and time consuming process. In India, most of the land filled sites are uncontrolled dumps. The garbage on such sites is not property maintained.

Improvements in our life style have resulted in greater amount of waste material production as many articles being used in our daily lives are disposable items. Changes in packaging have made majority of our wastes non-biodegradable which continue to degrade the environment and cause health hazards.

METHODS OF DISPOSAL OF SOLID WASTES:

(1)       RECYCLING: Articles collected by the rag pickers are re-cycled. For example from waste paper cardboard is made, metal wastes are melted to obtain fresh metal articles. Polythene is recycled, plastic is mixed with cement to make roads.

(2)       COMPOSTING; Garbage mixed with sewage, sludge is converted into compost. Organic wastes are decomposed anaerobically to obtain biogas and manure.

(3)       LAND-FILLING; Solid waste is dumped into low-lying areas compacted and covered with a layer of soil each time to reduce the foul smell and spread of diseases.

(4)       INCINERATION; Organic waste is aerobically burnt at 850 degree Celsius inside an incinerator.

(5)       BURNING; Solid combustible waste is burnt but this causes air pollution.