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The sum of physical and biological factors along with their chemical interactions that affect an organism is called environment.

Ozone layer is very important for the existence of life on earth because it absorbs most of the harmful ultraviolet radiation coming from the Sun and prevents them from reaching the earth. The ultraviolet radiations have extremely harmful effects on human beings, other animals as well as plants. For example, ultraviolet rays can cause skin cancer. They also damage the eyes by causing an eye disease called cataract. Ultraviolet rays damage immune system by lowering the bodys resistance to diseases. Thus, ozone layer in upper atmosphere protect us from these diseases by absorbing ultraviolet rays coming from the sun. This decrease has been linked to synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers. In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels. By developing substitutes to freeze CFCs; scientists have already developed some substitutes which are ozone friendly.

Two practices which can help in the protection of our environment are:
(i) Disposal of the waste after its separation as biodegradable and non- biodegradable material.
(ii) Judicious use of unleaded petrol and alternate sources of energy.

Ozone is present in the stratosphere. It protects the earth from harmful ultraviolet radiations. UV ray causes various diseases to organisms e.g. skin cancer, cataract in human beings. Ozone layer is depleting because of chlorides and fluorides. They act on ozone molecules and deplete it. Chlorides, fluorides are present in CFC’s which are used in refrigerants and fire extinguishers. 

CFC ⎯⎯→ Chlorofluorocarbon 

The precautions taken to preserve the ozone layer is to ban the use of CFC’s.

a. Ecosystem 

It is structural and functional unit of biosphere comprising of both biotic and abiotic components. 

b. Biomagnification 

The phenomenon of increase in concentration of harmful chemicals mainly nonbiodegradable toxic chemicals at every trophic level is called biomagnification.

Judicious use of aerosol spray propellants such as fluorocarbon and chlorofluorocarbons which cause depletion or hole in ozone layer. Control over large scale nuclear explosions and limited use of supersonic planes.

Ultraviolet rays from the sun penetrate down the earth and cause health hazards/skin cancer in human being.

The amount of Ozone in the atmosphere began to drop sharply in the 1980s. 

This decrease is due to the synthetic chemicals like chlorofluorocarbons which are used as refrigerants and in fire extinguishers. 

In 1987, United Nations Environment Programme, (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels.

(a) Because Ozone layer protects / shields earth from harmful UV radiations of the sun.

(b) Conducting, poster making competition, highlighting effects of ozone layer depletion.

Conducting street plays highlighting, the ways of environment protection.

Detailed Answer:

(i) Ozone layer helps in shielding the Earth from the harmful UV radiations condition from sun. If ozone layer gets depleted, UV radiation can directly reach the Earth's surface and drastically affect the life on Earth.

(ii) Ozone layer can be protected by :

(a) Stopping the release of Chlorofluorocarbon

(b) Removing the pollutant nitrogen monoxide

(c) Reduce the usage of air conditioners.

Ozone layer is found in stratosphere and above it is mesosphere. In this layer meteors burns up and this layer extends up to 85 km high.

Some substances are non-biodegradable because they cannot be broken down into simpler harmless substances in nature.

Ozone at higher level of atmosphere is a product of UV radiation acting on oxygen (O₂) molecule.

Ozone layer protects the earth from harmful radiations like high energy ultraviolet radiations from passing through it.

Importance of carbon dioxide gas: Carbon dioxide gas shows greenhouse effect and maintains the atmospheric temperature suitable for life on earth. It keeps the air hot. 

Importance of ozone layer: Ozone layer in the atmosphere absorbs the harmful radiations. Ultra-violet radiations, coming from sun prevents the life on earth from their harmful radiations that cause skin cancer, damage the new cells and create chromosomal disorder in the livings.

When UV radiations from the sun reach the earth’s atmosphere which is heavily rich in oxygen. Then these UV rays split molecular oxygen (O₂) into free oxygen (O). Afterward, this free oxygen reacts with molecular oxygen; it forms ozone (O₃).

O₂ \(\overset{UV}\longrightarrow\) O + O

O + O₂ → O₃

This ozone now protects the earth from harmful UV radiations of the sun, by allowing only some percent of rays to fall on the earth’s surface. Ozone acts as a filter of sun rays. These rays can cause skin cancer in human and can also affect other living organisms.

The chemical compound Chlorofluorocarbon is responsible for decrease of ozone in the upper atmosphere of the earth.

Ozone is a gas layer present in the stratosphere. This layer protects living beings on the Earth from harmful ultraviolet (UV) rays coming from the Sun. Without the layer of ozone in the atmosphere, it would be very difficult for anything to survive on the surface. Depletion of the ozone layer has consequences on humans, animals and plants.

The position of man is at the apex of most food chains as he is an intelligent organism and can take any advantageous position by manipulation. Also, man can eat any food and thus can be positioned at apex.

In an ecosystem biotic and abiotic factors are interdependent and interlinked. 

For example: The grass in grassland will grow only if it gets soil which can hold water and gets sunlight with proper temperature hence the grass grows in a place which has all abiotic factors responsible for its growth but in desert these abiotic factors are not available for the growth of grass.

(a) An eco system is a self contained unit of living things(plants, animals and decomposers), and their non living environment (soil, air and water). 

Example – a grassland and a forest. 

(b) 1. Biotic component – The biotic components of the ecosystem is a community of organisms which is made up of many different inter-dependent populations. It includes – producers, consumers and decomposers. 

2. Abiotic components – The abiotic components of the ecosystem (non living components) include the physical environment like soil, water and air alongwith the in organic substances like carbon dioxide, nitrogen, water and phosphorous.

The concentration of pesticide will increase with the rise of trophic level in the food chain.
Phytoplankton -----> Zooplankton ---> Small fish
-----> Big fish (maximum pesticide) 

Therefore, big fishes will have maximum amount of pesticides.

Decomposers are the organisms which act on dead organisms to decompose the body so as to release all the elements back to nature. 

They act as cleansing agents, hence they are important in the ecosystem.

The answer is (b) convert organic material to inorganic forms

1. b. Plastic bags

2. a. A natural forest

3. b. Animals

4. c. both living and non living components

5. a. Plant

The decomposers are considered as cleaner of the Earth. Decomposers such as bacteria and fungi break down or decompose dead and decaying organic matter into simpler or inorganic forms.

Correct answer is (d) All the above

Correct option  (D) Biomass in pond ecosystem

Explanation:

The pyramid shown here is an inverted pyramid. Pyramid of energy can never be inverted. Number of producers (i.e., phytoplanktons) in a pond are always more than the consumers thus, pyramid of number in a pond cannot be inverted. ln a forest, biomass of producers (i.e., tree) is large, so pyramid of biomass is upright in this case also. Pyramid of biomass for pond ecosystem is inverted as biomass of a trophic level depends on reproductive potential and longevity of its members.

• DDT is an insecticide and is non-biodegradable compound. 

• Once this insecticide sprayed in the environment, it stays for very long time and through food chain into the organisms. 

• According to the concept of biomagnification, the maximum accumulation of a nonbiodegradable pollutant is maximum in the highest trophic level. 

• Hence, DDT gets accumulates at each trophic level and since, man is at the highest trophic level, there is maximum accumulation of DDT observed in them.

Correct option  (D) Transfer of energy from one trophic level to other is associated with energy loss

Explanation:

The quantum of available energy in a food chain successively gets decreased at each trophic level as a result of energy loss. This limits the number of trophic levels in a food chain.

Plastic bag cannot be broken down by microorganisms. It will remain in the environment for many years. Paper is a biodegradable material is made from other natural products like fruits, plants etc. Hence paper can be degraded naturally by the action of microorganisms in a few months.

Plastic bag is not acted upon by decomposers as it cannot be broken down into simple components, so it is called non-biodegradable while paper gets decomposed.

(a) We take a piece of paper and a plastic bag (Polythene Bag). Now dig the ground to about 15 centimeters depth and place the piece of paper and plastic bag in the dug up ground separately. After a month, we dig up the buried material and observe them. We will find that the piece of paper has been partially eaten up but the plastic bag has been remained unaffected. This means that the paper have been decomposed by the micro-organisms present in the soil. So paper is biodegradable. On the other hand, the plastic bag has not been decomposed by the micro ?organisms present in the soil, therefore It is non-biodegradable. 

(b) It is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable and other are non- biodegradable.

1. b. Consumers

2. c. Because plants can produce its own energy

3. c. Grass → goat → human

4. a. Hunt for other animals

5. d. The deer is the prey

1. b. They are non-biodegradable

2. d. Plastic bags

3. b. It never fully goes away, it Rust breaks into little pieces

4. c. Both A and B

5. a. Oceans

(i) The existence of decomposers is essential in a biosphere because they breakdown complex organic substances into simple inorganic substances that can be absorbed by the plants.

 Thus, decomposer:

(a) replenish the soil naturally

(b) helps in removing the biodegradable waste.

(ii) In a food chain the energy moves progressively through the various trophic levels, it is no longer available to the previous level (autotrophs) and the energy captured by the autotrophs does not go back to the solar input.

Hence, the flow of energy is unidirectional.

(i) They help in the breakdown of organic matter or biomass of dead plants and animals into simple inorganic raw materials such as CO₂, H₂O and nutrients.

(ii) They help in the natural replenishment of soil. They help in keeping the environment clean.

Aerosol and CFCs are substances that posed a threat to the environment 

•Aerosol is a substance enclosed under pressure and released as a fine spray by means of a propellant gas. For example, body deodorant, any of spray. 

•CFCs or Chlorofluorocarbons are a group of man-made compounds containing chlorine, fluorine and carbon. They are harmful and cause depletion of ozone layer

Non-biodegradable substances are those which cannot be breakdown or degraded by microorganisms such as bacteria and fungi. Glass is no-biodegradable substance in above given substances.

Biodegradable substances are those which can be breakdown or degraded by microorganisms such as bacteria and fungi. Cotton, rubber and leather are biodegradable substances in above given substances.

These micro-organisms break down the complex organic substances into simple inorganic substances that go into the soil and are used once more by plants.

Ozone layer and how it is getting depleted. 

Ozone (O₃) is a molecule formed by three oxygen atoms. There is a layer of ozone in the stratosphere. It is a deadly poison. It is known to cause skin cancer in human beings. However, at the higher levels of the atmosphere, it acts as a natural sun-block and shields us from UV radiations of the sun which are dangerous to living organisms. Ozone depletion is the sharp reduction of ozone in the stratosphere due to chlorofluorocarbons (CFC’s) used as refrigerants and in fire extinguishers.

O₂ ------U.V----------→O+O

O+O₂ -----→ O3 (ozone)

To limit the damage to the ozone layer the release of CFC s into the atmosphere must be reduced. These CFCs should be replaced with environmentally safe alternatives.

Managing the garbage we produce:

Improvements in our lifestyle have resulted in greater amounts of waste material generation. Changes in packaging have resulted in much of our waste becoming non-biodegradable. Increased use of non-biodegradable items has left the environment polluted with them.

Correct answer is (a) fungi

Government of India is imposing a ban on the use of polythene bags because they cannot be degraded naturally by the action of microorganisms. Because of their non-biodegradability, they stay in the soil for a long time and continue to poison it with toxic by-products that keep leaching from them. Also, they do not allow water to seep in as they are waterproof. These polythene bags, when accidentally eaten by stray animals, can harm them and can even lead to their death.

Jute and cloth bags can be used in place of polythene bags. They are environment-friendly as they are biodegradable. 

They are renewable and can be easily recycled.Thus, using jute and cloth bags will help to reduce pollution.

The waste materials that we generate in our daily life are either biodegradable and nonbiodegradable. In our environment, microorganisms such as bacteria and fungi secrete enzymes to degrade substances. Organic compounds, present in the dead remains of plants and animals and their waste products can be degraded into simpler harmless substances by biological processes and microorganism. These wastes are termed as biodegradable. On the other hand, certain category of wastes like plastics, glass, etc. cannot be degraded by microorganisms or biological processes. These wastes persists in the environment and are termed as non biodegradable.

Industrial waste is the waste produced by industrial activity. It includes any material that is made useless during a manufacturing process. Some examples of industrial wastes are chemical solvents, sludge, metals, ash, paints, paper products, industrial by-products, metals, and various others. 

Industries are important for the economic growth and development of a society, but it can also be harmful to the environment. Industrial process can cause pollution to air, water and soil, health issues, extinction of species, and more. Disposing of waste has huge environmental impacts and can cause serious problems like:

Air-Emissions 

Industry is a major cause of air pollution, as it results in the emission of pollutants, including organic solvents, respirable particles, sulfur dioxide (SO₂) and nitrogen oxides (NOX). These pollutants can both harm public health and damage the environment in ways like the greenhouse effect, ozone hole. 

Wastewater 

The sources of effluent- treated or untreated wastewater that is discharged into surface waters - are many and varied. Untreated wastewater can cause environmental problems including: pollution of groundwater reservoirs, damage of transport and wastewater treatment systems, and degradation of treated wastewater and sludge such that it would disqualify them from being used for agricultural purposes. 

Land-Pollution 

Leakage from the fuel and energy industries, as well as industries involving hazardous materials, is the main causes of land contamination. Soil contamination is caused by direct exposure to the pollutant, leakage of toxic gases into buildings, and groundwater pollution. The properties of soil result in pollutants remaining in the soil long after the pollution incident. It is taken up by various plants and then it is consumed by humans, causing various health effects. 

Hazardous-Materials 

Hazardous materials are widely used by almost all the industries. If not properly treated, stored, or dealt with, hazardous materials can cause damage to human health, environment and property. 

Radiation 

Human and the environment are at-risk from exposure to both ionizing radiation (sources include radioactive materials, x-ray machines, and accelerators) and nonionizing radiation (from electrical installations, mobile broadcasting centers and lasers). 

These harmful radiations can cause many health hazards like skin cancer, cataract, destruction of plants, etc.

(a) The micro-organisms which break down the complex organic compounds present in dead  organisms like dead plants and animals and their products like faeces, urine, etc., into simpler  substances are called decomposers. 

Example – Bacteria and Fungi.  

(b) The decomposers help in decomposing the dead bodies of plants and animals, and hence  act as cleansing agents of environment.

Two ways in which non-biodegradable substances would affect the environment are:
(i) Some of the non-biodegradable wastes (pesticides and heavy metals) convert the land into barren land and enter the food chain thus, effecting human beings and other biotic components of the environment.
(ii) Pesticides and other chemicals enter water and food chains. They affect the fertility of soil and harm all kind of living organisms. Human beings are harmed the most because they are at the top of the food chain.

1. As these are not decomposing, they cause air pollution and water pollution.

2. Plastic enters stomach of many animals and causes death of animals.