Chapter Number 16 Man and His Environment – 10th Class Biology Notes

Question 1: Define the following terms?

(1) Environment (2) Habitat (3) Ecology (4) Niche (5) Conservation. (6) Biomass.

Answer: (1) Environment: The surrounding of an organism is called environment. Environment includes all the biotic and abiotic factors that influence an organism.

(2) Habitat: The specific locality with a particular set of environment where an organism lives is called environment.

(3) Ecology: The study of relationship of an organism with each other and their environment is called ecology.

(4) Niche: The ecological rule which a species plays within an environment is called ecological niche.

(5) Conservation: Maintaining natural resources of environment and their careful use is called conservation.

(6) Biomass: The total amount of living or organic matter in an ecosystem at any time is called “biomass”.

Question 2: What are different levels of ecological organization?

Answer: Levels of ecological organization: Levels of ecological organization ranges from individual organism to Biosphere.

 Species or individual organism: Organisms that can freely interbreed and produce fertile offsprings are called species. Example: man.

 Population: Group of individual of the same species living together in the same area and sharing the same resources is called population. Example: Human population, Population of mustard plants.

 Community: A group of different species or different populations is called community. Example: Forest community.

 Ecosystem: The self-sufficient unit of an environment that is formed as a result of interactions between its biotic community and the abiotic components is known as an ecosystem. Ecosystem is the basic structural and functional unit of ecology.. Ecosystem may be natural or artificial. Aquarium, Zoo and Botanical garden are examples of artificial ecosystem while A pond, a lake and a forest are examples of natural ecosystems.

 Biosphere: All ecosystems of the world together form the biosphere. It includes all the ecosystems of the planet Earth. In other words, the biosphere consists of all organisms present on the Earth and all regions of the Earth where they live.Biosphere ranges from the floor of oceans to the tops of the highest mountains. It is about 20 kilometres thick.


Question 3: What are the components of ecosystem?

Answer: An ecosystem consists of two basic parts (components).

  1. A) Abiotic components. (B) Biotic components.

Abiotic components: The abiotic components include the non-living factors present in ecosystem. The important non-living factors are light, air, water, soil, fire, gravity, humidity and the basic elements and compounds.

Biotic components: The biotic components comprise the living part (organisms) of the ecosystem. These include plants, animals and microorganisms. Biotic components are further classified into three types.




Producers: The producers are the autotrophs present in an ecosystem. Producers include plants, algae and photosynthetic bacteria. These organisms are able to synthesize complex organic compounds (food) from inorganic raw materials. Producers use sunlight energy, CO2 and H2O to prepare food. Producers form the basis of any ecosystem. In terrestrial ecosystems, plants (e.g. populous) are the main producers. In aquatic ecosystems, the main producers are the floating photosynthetic organisms (mainly algae) called phytoplankton and shallow water rooted plants.

Consumers: The consumers are heterotrophs. They cannot synthesize their food and so depend upon producers for food. Consumers include all animals, fungi, protozoans and many of the bacteria. The animals are the major consumers of ecosystems. They are further classified as herbivores and carnivores.

Herbivores (Primary consumers): The animals that feed directly on plants (producers) or plant products are called herbivores. E.g. cattle, deer, rabbit, grasshopper etc. feed on plants.

Carnivores: Carnivores are the animals that feed on other animals. So they are flesh eaters. Carnivores are further of following types.

Primary carnivores or secondary consumers: These animals feed on herbivores animals. Examples: Lizard, Frog, Fox, Predatory birds, many fishes and snakes.

Secondary carnivores (Tertiary consumers): They feed on secondary consumers (primary carnivores). Examples: wolf and owl.

Tertiary Carnivores (Quaternary consumers): They feed on secondary carnivores (Tertiary consumers). Tertiary carnivores are not eaten by any other animals so they are also called top carnivores. Examples: Lion, Tiger, etc.

Omnivores: Some animals eat both plants and animals and are called omnivores. Examples: Man, crow, ants, etc.


Decomposers (Reducers or Saprophytes): Decomposers or reducers break down the complex organic compounds of dead matter (of plants and animals) into simple compounds. They secrete digestive enzymes into dead and decaying plant and animal remains to digest the organic material. After digestion, decomposers absorb the products for their own use. The remaining substances are added to environment. Many types of bacteria and fungi are the principal decomposers of biosphere. The minerals, which are released by decomposers, are used as nutrients by the producers.






Interesting information:The biosphere makes a thin layer surrounding the planet Earth. If you consider the Earth as of the size of an apple, then the biosphere will be as thick as the apple’s skin.



Question 4: Describe flow of materials and energy in an ecosystem?

Answer: Flow of materials and energy in an ecosystem: Energy is required for the performance of all activities. Existence of living organisms depends upon flow of energy and circulation of materials.



Flow of Energy and sun as principal source of energy: Light is ultimate source of energy. This energy is called solar energy. Sunlight energy is converted into chemical energy by plants through photosynthetic process. They store this energy in their tissues and also transform it into mechanical and heat energy during their metabolic activities.


The energy in producers’ tissues flows to herbivores when producers are eaten. Herbivores transform it into mechanical and heat energy during their metabolic activities and store the rest in their tissues. Carnivores eat herbivores and get energy. They also use it for their body activities and store the rest in their tissues. After the death of producers and consumers, the energy stored in their tissues is used by decomposers.

The flow of energy in an ecosystem is unidirectional.


The storage and expenditure of energy in an ecosystem is in accordance with the basic law of thermodynamics i.e. ‘energy can neither be created nor destroyed but can be transformed from one form into another’. In an ecosystem there is,

  • Constant flow or transfer of energy from the Sun through producers to consumers and decomposers.
  • A significant decrease in useful energy during transfer of energy at each trophic level.



Figure : Energy flow in an ecosystem




Flow of Materials

The materials flow from one trophic level to the next by means of food chains and food webs.



Food chain: The process of eating and being eaten is called food chain. A food chain is a series of organisms within an ecosystem, in which each organism feeds on the one before it and is fed by the one after it. For example, following is a food chain in an ecosystem:


Figure: A simple food chain



The base of food chain is always formed by a plant (producer). It is eaten by a primary consumer, which is preyed upon by a secondary consumer. The secondary consumer may be eaten by a tertiary consumer. A food chain, can therefore, be represented as,


Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer


A food chain involves a nutritive interaction among the biotic components of an ecosystem. Usually there are 4 or 5 trophic levels. Shorter food provide greater available energy and vice – versa.

A food chain may be simple or complex. It may be also terrestrial or aquatic.


Food web: “a network of food chains which are interconnected at various trophic levels.” In nature, food chains are very complex, as one organism may be the food source of many other organisms. Thus, instead of a simple linear food chain, there is a web-like structure formed by these interlinked food chains. Such interconnected food chains collectively make ‘food web’.



Figure : A food web in grassland ecosystem



Analyzing and Interpreting:

• Construct food chains and food webs through observation of a local pond or grassland ecosystem



Question 5: Explain what do you mean by the pyramids of number and biomass?


Answer: Ecological pyramid: “A representation of the number of individuals or amount of biomass or energy present in various trophic levels of a food chain”.

Explanation: In 1927, Charles Elton (an English ecologist) developed the concept of ecological pyramids. He noted that the animals present at the beginning of food chain are abundant in number while the animals present at the end of food chain are fewer in number.



Types of Ecological pyramid: Ecological pyramids are of three types.

Pyramid of Numbers.  (2) Pyramid of Biomass.  (3) Pyramid of energy.


  1. Pyramid of Numbers:

It is the graphic representation of the number of individuals per unit area at various trophic levels. Number of organisms decreases from first trophic level upto 4th trophic level gradually. So organisms in first trophic level (producers or plants) are present in large number, primary consumers are in lesser number, secondary consumers are fewer, and so on. So, the producers are of smallest size but maximum in number, while the tertiary consumers are larger in size but lesser in number (Fig. 16.5).




Figure : Pyramid of numbers in an ecosystem



  1. Pyramid of Biomass:

It is the graphic representation of biomass present per unit area at different trophic levels. The total amount of living or organic matter in an ecosystem at any time is called “biomass”. In a terrestrial ecosystem, the maximum biomass occurs in producers, and there is progressive decrease in biomass from lower to higher trophic levels.




Figure : Pyramid of biomass in an ecosystem.


(3)Pyramid of Energy: Pyramid of energy means that the energy usually decreases from first trophic level to 4th trophic level. First trophic level has more energy while top trophic level has less energy.



Question 6: Write a note on Carbon cycle.



Biogeochemical Cycles: Biogeochemical cycles are the cyclic pathways through which materials move from environment to organisms and back to environment.


  1. Carbon Cycle: The combined processes, includingphotosynthesis, decomposition, andrespiration, by which carbon as a component of various compounds cycles between its major reservoirs—the atmosphere, oceans, and living organisms is called carbon cycle.

Carbon atom is the principal building block of many kinds of biomolecules. Carbon is found as graphite and diamond in nature. It also occurs as carbon dioxide in atmosphere and in water.

Major source of carbon for the living world is carbon dioxide present in atmosphere and water. Fossil fuels like peat, coal, natural gas and petroleum also contain carbon. Carbonates of Earth’s crust also give rise to carbon dioxide.


The major process that brings carbon from atmosphere or water into living world is photosynthesis. Producers take in carbon dioxide from atmosphere and convert it into organic compounds. In this way, carbon becomes a part of the body of producers. This carbon enters food chains and is passed to herbivores, carnivores and decomposers.

Carbon dioxide is released back to environment by respiration of producers and consumers. It is also released by the decomposition of organic wastes and dead bodies by decomposers. Burning of wood and fossil fuels also adds large amount of carbon dioxide into atmosphere.




Figure : Carbon cycle




For Your information: The balance of carbon cycle has been upset by human activities such as deforestation and excessive burning of fossil fuels. As a result, the amount of carbon dioxide in atmosphere is increasing, causing the greenhouse effect and global warming.


Question 7: What are the different stages of Nitrogen cycle?


  1. Nitrogen Cycle

Nitrogen is an important component of many biomolecules, like proteins and nucleicacids (DNA and RNA). Atmosphere is the reservoir of free gaseous nitrogen. Living organisms cannot pickup this gaseous nitrogen directly from atmosphere (except for nitrogen fixing bacteria). It has to be converted into nitrates to be utilised by plants. Nitrogen cycling involves several stages


Formation of Nitrates: It is done by the following ways.

Nitrogen Fixation.

Ammonification and Nitrification.



Nitrogen Fixation: Conversion of nitrogen gas into nitrates is called nitrogen fixation. It occurs in the following ways.

  • Thunderstorms and lightning convert atmospheric gaseous nitrogen to oxides of nitrogen. These oxides dissolve in water and form nitrous acid and nitric acid. The acids in turn combine with other salts to produce ‘nitrates’. It is called asatmospheric nitrogen fixation.
  • Some bacteria also have the ability to transform gaseous nitrogen into nitrates. It is calledbiological nitrogen fixation.Some of these nitrogen fixing bacteria live as symbionts and many are free-living.

Nitrogen fixation is also done in industries. In industrial nitrogen fixation, hydrogen is combined with atmospheric nitrogen under high pressure and temperature. It produces ammonia which is further converted into ammonium nitrate.


Ammonification and Nitrification: Ammonification is the breakdown of the proteins of dead organisms and nitrogenous wastes (urea, uric acid etc.) to ammonia. It is done by ammonifying bacteria. After the formation of ammonia, it is converted into nitrites and nitrates. It is called nitrification and is done by nitrifying bacteria. First, ammonia is converted into nitrites by bacteria (e.g. Nitrosomonas). The nitrites are then converted into nitrates by other bacteria (e.g. Nitrobacter).


b- Assimilation

The nitrates formed by the above processes, are absorbed by plants and are utilized for making proteins etc. Animals take nitrogenous compounds from plants. The utilization of nitrates by organisms is called assimilation.


c- Denitrification

It is a biological process in which nitrates and nitrites are reduced to nitrogen gas by denitrifying bacteria. By this process, nitrogen is returned to atmosphere.







Excessive denitrification reduces soil fertility and is stimulated by water logging, lack of aeration and accumulation of organic matter in the soil.





Question 8: Write notes on competition, predation and symbiosis.





 Interactions in Ecosystems: All organisms need energy to perform their functions properly. For this purpose organisms interact with each other, as organisms are dependent on one another. These interactions may be useful or harmful for one or both organisms. Interactions are of two types on the basis of species relationships.

Intraspecific interactions: The interactions between the members of the same species are called intraspecific interactions. Example: Interactions between human species.

Interspecific interactions : Interactions between the members of different species are called interspecific interactions. Example: Interactions between human species and mustard species.

Interspecific and Intraspecific interactions are further devided into following sub-types.

Competition: Type of interaction in which organisms compete for various needs like food, water and space with each other is called competition.

Types of Competition: Competition is further divided into two types.

Intraspecific competition: The competitions between the members of the same species are called intraspecific competition. Example: competitions between human species.

Interspecific Competition : competitions between the members of different species are called interspecific competition. Example: competitions between human species and mustard species.

Intraspecific competition is always stronger and more severe than the interspecific competition.


Importance of competition: Competition helps in maintaining a balance between the available resources and the number of individuals of a species.


Predation: The relationship in which one organism kill the other for its food is called predation. It is an interaction between two animals of different species or between a plant and an animal. In predation the large organism that kills the other is called predator while the organism that is used as food is called prey.

All carnivore animals are predators. For example, frog preys upon mosquito and fox preys upon rabbit. There are some examples where a predator is preyed upon by a second predator and then the second one is preyed upon by a third predator. For example, frog (predator 1) is preyed upon by a snake (predator 2) and the snake is preyed upon by an eagle (predator 3). Plants also show competition for space, light, water and minerals. • Certain plants (Pitcher plant, sundew, Venus fly trap etc.) are carnivorous and live as predators (Fig. 16.10). Such plants live in the areas where minerals and other nutrients are lacking. They feed on insects to fulfil their nitrogen requirements. These plants have mechanism to attract insects. For example, they secrete sweet nectar that attracts the insects searching for food. Their leaves are also modified to capture the prey.


Importance or advantages of predation or effects on the population growth : Predation keeps the prey population under check, so as to maintain an ecological balance. Humans benefit from this interaction in the biological control of weeds and pests. In order to control pests in an area, their predators are released there.






Figure: Examples of predators and their preys





Figure : Predator Plants




Symbiosis: (symbios means living together). It is a relationship between members of different species, in which they live together for longer or shorter periods of time. Symbiosis is of three types.


Parasitism: (positive-negative interaction). It is a type of symbiosis (between members of different species), in which smaller partner (parasite) derives food and shelter from the body of larger partner (host) and, in turn, harms it. In this type of interactions parasite benefited while the host get harm.

Types of parasitism: Parasitism is of two types.

Temporary parasitism: In this type of parasitism the parasite spends most of its life cycle as independent free-living organisms. Only a part of its life cycle is spent as a parasite. Leech, bed bug, mosquito are common temporary parasites of humans. These types of parasites are called temporary parasites.

Permanent parasitism: In permanent parasitism, the parasites spend their whole life cycle as parasites. Many disease causing bacteria and all viruses are permanent parasites. These types of parasites are called permanent parasites.


Parasites may also be classified as ectoparasites and indoparasites.

Ectoparasites: Parasites that live outside or on the surface of host body and get food from there are called ectoparasites. Mosquitoes, leeches, lice etc. are the examples of ectoparasites.

Endoparasites: Endoparasites live inside the body of host and get food and shelter. Bacteria, viruses, tapeworm, Ascaris, Entamoeba, Plasmodium etc. are the examples of endoparasites.


Parasitic plants: Some plants (e.g. Cuscuta, also called dodder) are parasites on other plants.

Parasitic plants grow special types of roots (haustoria) into host body and suck the required nutrients from the vascular tissues of host. Host can survive without parasite, but parasite cannot survive without host.



Figure : Ectoparasites




Figure : Some endoparasites




Figure : A parasitic plant and its host tree trunk


Mutualism: (positive-positive interaction). In this type of symbiotic interaction, both partners (of different species) get benefit and neither is harmed. For example, Termites eat wood but are not able to digest it. A protozoan lives in its intestine. It secretes ‘cellulase’ enzyme to digest the cellulose of. In return, the termite provides food and shelter to the protozoan. The nitrogen fixer bacteria Rhizobium live in the root nodules of leguminous plants like pea, gram etc. The bacteria obtain food and shelter from plants while in return they fix gaseous nitrogen into nitrates for the plant which is required for their growth.



Figure 16.14: Termite, with a protozoan in its gut Figure 16.15:Bacteria in root nodules


Commensalism: (positive-neutral interaction).

  • It is a type of symbiosis in which one partner is benefited while the other is neither benefited nor harmed. For example:
  • Epiphytes are small plants found growing on other larger plants for space only (Fig. 16.16-a). They absorb water and minerals from atmosphere and prepare their own food. The larger plants are neither benefited nor harmed in any way.
  • Sucker fish attaches to the surface of sharks by its sucker (Fig. 16.6-b). In this way, the shark provides easy transport to the sucker fish to new feeding grounds.




Figure : a– An epiphyte orchid plant growing on a tree trunk; b- A sucker fish attached with shark



What type of symbiosis is it?

The honeyguide bird feeds on wax and the larvae present in honeycombs. It flies around looking for honeycombs, but it is not strong enough to open the comb. Badgers are large mammals that feed on honey. When a honeyguide bird goes to find honeycombs, the badger follows it. When the bird finds a honeycomb, it calls the badger. Sometimes the bird has to stop and wait for the slow-moving badger. After reaching there, the badger opens the honeycomb and both of them eat their foods together. Traditionally, humans have also used these birds to find honeybee colonies.




Question 9: Explain how human activities have contributed to the loss of balance in nature. Explain overpopulation and urbanization with reference to Pakistan?


Answer: Ecosystem Balance And Human Impact: Balance of an ecosystem means that the kind and the number of an organisms are maintained consistently in an ecosystem. In an ecosystem  many types of organisms living together and can interact with environment and a balance is developed. Human beings impact this ecological balance by different ways and modify the environment. These human activities include cutting of plants (deforestation) , etc.

Impacts of man on ecosystem are as follows.

Global warming. (2) Acid rain. (3) Deforestation. (4) Urbanization.


Global Warming: The increase in temperature of earth and its atmosphere due to addition of green house gases is called global warming.

Phenomenon or mechanism of global warming: The global warming is due to some gases. Green house gases are corbon dioxide, methane and ozone. These gases remains in the lower part of earth,s atmosphere and donot allow solar radiations to reflect back into space. As a result heat remains within the earth atmosphere and increase its temperature. This is called global warming.



Effects of global warming

  1. 1. Accumulation of carbon dioxide in air is resulting in increasing atmospheric temperature about 0.05 °C every year.
  2. 2. It is causing major changes in weather patterns. Extreme weather events are occurring more commonly and intensely than previously.
  3. 3. It melts glaciers and snow caps that are increasing flood risks and intense tropical cyclones.
  4. 4. Sea-level is rising due to which low lying areas are liable to be submerged, turning previously populated areas no longer habitable.
  5. 5. Soil water reduces.

Example: The Maldives’ Survival: Scientists fear that the sea level is rising up to 0.9cm a year. Rise in sea level has worst effects on coastal countries. Most of the islands of the Maldives are less than 1 metre above sea level. It is estimated that within 100 years, the Maldives might become uninhabitable and the citizens would be forced to evacuate.


In 1990, the United Nations

established Intergovernmental Panel on Climate Change (IPCC). It provides scientific advice to the world leaders on issues like the build-up of greenhouse gases and its prevention. According to IPCC, Earth’s surface temperature has increased ≈0.2°C

per decade in the past 30 years.


Greenhouse Effect: The term ‘Greenhouse Effect’ refers to the phenomenon in which certain gases (called greenhouse gases) trap heat in the atmosphere. These gases act like the glass in a greenhouse, which does not allow the inner heat to escape. When sunlight reaches the surface of the Earth, much of its energy is transformed into heat energy. The Earth surface reflects this heat energy towards space as infrared radiation. The greenhouse gases trap infrared radiation and send it back to Earth. Carbon dioxide, methane and nitrous oxide are important greenhouse gases. Since 1800, the amount of Carbon dioxide in atmosphere has increased 30 %. The amount of methane has more than doubled and the amount of nitrous oxide has increased about 8%.



Acid Rain: Rain that contains acid particles is called acid rain.

Reasons of acid rain: Burning of fossil fuels produces oxides of sulphur and nitrogen in air. Rain water SO2 and SO3 into H2SO4 and NO2 and NO3 into HNO2 (nitrous acid) and HNO3 (nitric acid). Normal rain water is weakly acidic due to the presence of dissolved CO2 in it. Its PH is 5.6 to 6. The addition of air pollutants makes rain more acidic that ranges PH from 3 to 6 (mostly reduces to 4).



Effects of Acid rain: Some of the significant ill effects of acid rain are:

  • Acid rain destroys the necessary nutrients present in the waters of rivers and lakes etc. Its also lowers the pH of water. Most of the aquatic animals cannot survive at this pH.
  • Acid rain washes nutrients out of soil, damages the bark and leaves of trees and harms root hairs. Leaf pigments (chlorophyll) are also destroyed.
  • Metallic surfaces exposed to acid rain are easily corroded. Fabrics, paper and leather products lose their material strength or disintegrate easily.
  • Building materials such as limestone, marble, dolomite, mortar and slate are weakened with acid rains because of the formation of soluble compounds. Thus, acid rain is dangerous for historical monuments. The building of famous Taj Mahal has been corroded at many places, due to acid rains.




Figure: Taj Mahal and its corroded door



Deforestation: Deforestation means clearing of forests by natural causes or humans. “OR” Unplanned or unwise destruction and removal of trees is called deforestation.

Reasons of deforestation: (1) Large areas of forests have been cleaned for agriculture, factories, roads, rail tracks and mining. (2) Humans cut trees for getting wood (lumber), which is then used for making structures and for heat production. (3) Human preys upon forest animals, which are the predators of many insect pests. In this way, insect pests destroy forests by eating the shoots and spreading diseases.

Effects of deforestation: The effects of deforestation include floods, droughts, landslides and soil erosions, global warming and loss of habitat of many species and seasonal changes.


Overpopulation: Too much increase in the number of individuals in an area, so that it can cause depletion of natural resources is called overpopulation.

Industrial revolution started some 250 years ago,when the world population was at 600 million – that seems like a lot of people but now the world population is almost ten times at 6 billion and will grow to 8 billion by 2025. Better health facilities and lowered mortality rates have contributed in population growth.



Overpopulation in Pakistan: Pakistan is one of the developing countries and population increase day by day with a rapid rate. Following chart shows the population growth in Pakistan with the passage of time.



Year Population Year Population
1981 85,096,000 1999 134,790,000
1984 92,284,301 2002 144,902,409
1987 99,953,232 2005 155,772,000
1990 107,975,060 2008 166,111,487
1993 116,444,165 2009 169,708,303
1996 125,409,851 2010 173,510,000






Pakistan Population Growth Rates

Source:Pakistan Economy survey

Minidtry of Population Welfare

Government of Pakistan




Pakistan Urban population in %age

Source: The world Bank




For your information:

Mortar (Masonry): A material used to fill the gaps between the blocks and bind them together. Mortar is also a weapon that fires mortar bomb.





  1. Urbanization: The formation and growing of cities is called urbanization. The current level of urbanization in Pakistan is 32% which is not too much high by global standard.

Reasons of Urbanization: People migrate from rural areas to cities due to following reasons.

To obtain a better job.

For higher education and standards of life.

For business purpose.

To obtain better facilities, like gas, electricity, etc.



Effects of urbanization:

(A) Due to rapid urbanization the government find it difficult to provide even the basic facilities like health, education, shelter, clean water and electricity.

(B) Most of the migrants in cities do not find good jobs and become the part of urban poor.

(C) There is overcrowding in schools, hospitals etc.

(D) The slum areas increase in number and people living there are at greater risk of diseases.


Solution of Urbanization:


Urbanization is a global problem and cannot be stopped but it can be managed. A planned urbanization can solve many problems. Following measures can help to manage urbanization.

  • The cities should have thick green belts in their surroundings to control pollution.
  • The open spaces in cities should be reserved through zoning and land plans.
  • The urban spread-out should also be controlled.
  • Utilization of public transport instead of individual transports also proves effective way to manage urbanization.





Question10: Write note on the causes and effects of the air and water pollutions.



Pollution: Pollution is defined as any undesirable change in the physical, chemical or biological characteristics of air, water and land that may harmfully affect living organisms and natural resources.

Pollutants: Substances that cause pollution are called pollutants. E.g. CO2, CO, NO2, etc.


Air Pollution: Change in composition of air by the addition of harmful substances such as industrial wastes, automobile gases and particulate matter.  “OR” A change in characteristic of air that is harmful to living organisms is called air pollution.


Sources of air pollution: All sources of air pollution are related to human activities. Following are important sources of air pollution.




Burning of coal produces a lot of smoke and dust.

Burning of petroleum produces sulphur dioxide.

Forest fire and burning of wood produces a lot of CO and CO2.


Industries: Different industries produce air pollutants in the following ways.

Fertilizer industries: Fertilizer industries produce oxides of sulphur and nitrogen, hydrocarbons, particulate matter and fluorine.

Thermal industries: Thermal industries are coal based and their pollutants are fly ash, soot (soot is impure carbon particles resulting from incomplete combustion of hydrocarbons) and sulphur dioxide.

Textile industries: Textile industries releases cotton dust, nitrogen oxides, chlorine, smoke and sulphur dioxide.

Steel industries: steel industries releases SO2, CO2, CO, Phenol, fluorine, Cyanide (e.g. sodium cyanide NaCN), particulate matter, etc.


For your information:

Particulate matter: Particulate matter is the sum of all solid and liquid particles suspended in air.





Effects of Air Pollution: Following are the main effects of air pollution.

Global warming: components of air pollution increase in temperature of atmosphere so it is the result of global warming.

Smog formation: When pollutants like hydrocarbons and nitrogen oxides combine in the presence of sunlight, smog is formed. This is a mixture of gases. It forms a yellowish brown haze especially during winter and hampers visibility. It also causes many respiratory disorders and allergies as it contains polluting gases.

Acid rains: The air pollutants like sulphur dioxide and nitrogen oxides react with water in the atmosphere producing acid rains.

Ozone depletion: The upper layer (stratosphere) of the atmosphere has ozone (O3 ) which absorbs ultraviolet (UV) rays present in the sun’s radiation. However, the air pollutants like chlorofluorocarbons (CFCs) destroy the ozone molecules and so break the ozone layer. Ozone holes are created which permit UV rays to reach the Earth’s surface. The UV rays increase the temperature and also cause skin cancers.

Damage to buildings: The acid rain due to atmospheric pollution cause damage to buildings.

Diseases: Various diseases are also caused by air pollution like asthma, suffocation, irritation. These problems are due to oxides of sulphur and smug.


Control of Air Pollution:

For effective control of air pollution, it is important to create public awareness about the ill-effects of air pollution. Air pollution can be controlled by the following ways:

Afforestation: It means the establishment of new forests by planting on non-forest areas. Forests are effective means to control air pollution because plants can filter and absorb air pollutants

Modification of industrial effluents: The air pollutants coming from industries should be passed through filters and other devices, so that the particulate matter is removed before the waste gases are released out. The smoke producing units should have long chimneys to take the polluting gases far above and then disperse over a larger area. Industries should also invest for solar cookers or for producing bio gas.

Environment friendly fuels: Lead-free fuels should be used in automobiles. Similarly, sulphur-free fuel should be used in coal-based industry to reduce pollution by sulphur dioxide.




The substances that actually cause pollution are called the pollutants. They may be the industrial effluents, domestic wastes, medical wastes etc. Pollutants are of two types i.e. biodegradable and non-biodegradable.


Unwanted, unpleasant and annoying sounds are termed as noise. Noise is also considered as a form of pollution. Immediate effects of noise pollution are annoyance and aggression and the long term effects are hearing loss, depression, hypertension etc.


According to estimates, at the current rate of increase, the average

global temperature will go up by 3oC to 8oC in the next 100 years.


The harmful effects of the UV rays are visible in the countries such as Australia and New Zealand where the rate of skin cancer is higher than the other regions of the world.








Water Pollution: Any change in the composition of water by the addition of harmful substances is called water pollution.

Causes OR sources OR reasons of water pollution:

Sewage is one of the major pollutants of water. It contains organic matter and the excreta of human and other animals. Organic matter encourages the growth of microorganisms which spread diseases.


Industrial wastes: The wastes of industries contain acids, alkalis, dyes and other chemicals are disposed in nearby water bodies. These wastes change the pH of water and are harmful or even fatal to aquatic organisms. Hot water from cooling plants of the industries releases to water bodies and kill the aquatic organisms.


Agricultural wastes: Fertilizers and pesticides enter into water bodies with the rain water flow and the ground water by seepage. These chemicals remain in water for a long time and disturb food chain by causing diseases in animals and by killing them.


Oil tankers: Oil tankers and offshore petroleum refineries cause oil leakage into water. Oil floats on the water surface and prevents atmospheric oxygen from mixing in water. So, aquatic animals begin to die due to oxygen shortage.


Heavy metals: Some heavy metals like lead, mercury, arsenic and cadmium also make the water polluted and enter into body of plants and animals. When human and other animals use these vegetables or plants. They suffer from various diseases. These heavy metals contaminated water effects life in the following way.


Heavy metals reduce growth and development.

It causes cancer.

It causes nervous system disorders.

Mercury and lead cause joints diseases like rheumatoid arthritis. Mercury and lead also cause kidney disease and circulatory system disorders.


Effects of Water Pollution:

The following are major effects of water pollution.

Eutrophication: Enrichment of water with inorganic nutrients (nitrates and phosphates) is called eutrophication. The sewage and fertilizers contain large amount of inorganic material (nutrients). When sewage and fertilizers reach water bodies, the nutrients present in them promote algal blooms (excessive growth) there. Rich algal growth leads to increase in the number of the decomposers. Decomposers use the oxygen present in water and it results in the depletion of oxygen. Algal bloom also reduces the light reaching the lower layers in water.


Food chain contamination: The non-biodegradable water pollutants may stay in water for long times. From water, they enter into the body of small organisms, which are fed upon by fish. The fish in turn are fed upon by land animals including human. Thus humans suffer from various diseases.


Epidemics: Organic pollutants in water facilitate the growth of germs. Such polluted water causes epidemics like cholera, gastroenteritis etc.


Control of Water Pollution: Water pollution can be controlled by following ways.

Public awareness: Public should be made aware of the dangers of water pollution.

Treatment of sewage: Sewage water should be treated through sewage treatment techniques.

Treatment of industrial wastes: Industrial wastes should be treated before they are released into water bodies.


Question 11: What is land pollution? Explain reasons of land pollution along with their control measures?


Land Pollution: The change in characteristics of land or soil due to addition of unwanted materials that is harmful to living organisms is called land or soil pollution. The change in characteristics means change in PH, composition, color and odor of land.


Reasons or causes of land pollution: Important reasons of land pollution are as follows.


Pesticides: The pesticides used in agriculture have chemicals that stay in soil for long times and effect normal properties of land and soil.

Acid rain: The acid rains change the pH of soil making it unsuitable for cultivation.

Household and city garages: The household and other city garbage lies scattered in soil in the absence of a proper disposal system. Materials like polythene bags block the passage of water into soil and so decrease the water holding capacity of soil.

Industrial chemicals: Many industries produce harmful chemicals which are disposed of without

proper treatment.

Nuclear wastes: Improper disposal of nuclear wastes also causes radioactive substances to remain in soil for a long time.

Open latrines in villages and some parts of cities are also the source of land pollution.




Figure : Can we control land pollution?




Control of Land Pollution: Land pollution can be controlled by the following ways.

There should be suitable and safe disposal of wastes including nuclear wastes, domestic wastes, etc. Non-biodegradable materials like plastic, glass, metals etc. should be recovered and recycled.

Inorganic pesticides should be replaced by organic pesticides.




Question 12: Explain conservation of natural resources? Also explain R3 principles and plans for conservation of nature?

Answer: Conservation of Nature:

Conservation of nature means the conservation of natural resources of environment. It means that wise use of natural resources is basically the conservation. Natural resources include all those materials that we use in our daily life, like food, petrol, etc. The natural resources are of two types.

Renewable resources: These include all those resources that can be renewed. These cannot be depleted and can be recycled. These can be judiciously used. These include air, water, etc.

Non-Renewable resources: These include all those resources that cannot be renewed. They cannot be replenished once get depleted. Examples of these resources are minerals, fossil fuels, etc.

Conservation of natural resources of environment: To ensure sustainable use of resources in our environment, we should act upon the principle of ‘The 3R’ i.e. Reduce, Reuse, and Recycle.



The R1: Reduce: We should use the natural resources less and should not waste them. We should use this principle at different places, in our daily lives.

Water: We should not waste water.

◎ We should turn off the tap when not in use.

◎ We should bathe with a bucket instead of shower.

◎ There is no need to keep water running while brushing your teeth.

  1. B) Electricity:◎The lights and fans should be off, when we are not in room.

◎ Use natural light (sun) when possible during the day.

◎ Use energy savers light instead of other common bulbs.

  1. C) Fuel:We should take public transport (like buses) or walk short distances instead of using motor fuel.
  2. D) Food:We should not waste food and should give unused food to poor people.



The R2: Reuse: According to R2 principle, We should use things again and again. We should not throw away materials such as glass containers, plastic bags, paper, cloth etc. These should be reused at domestic levels rather than being thrown. It also reduces solid waste pollution.


The R3: Recycle: Recycling is a process to change materials into new products to prevent waste of useful materials to reduce the energy usage. “OR” Recycling is the re-processing of waste into its original state from which new useful items can be produced. Materials such as paper, plastic, glass etc. can be recycled. This decreases the volume of refuse and helps in the conservation of natural resources.


Interesting information: The R4: We can add the R4 i.e. Reforest. Trees should be planted during the rains. Trees make our environment more cool, shady and green.



For Your information: A recycling of one tonne of paper can save 17 trees.



For your information: Clean water, air, fuels, agricultural land and forests appeared to be plentiful earlier, but now these are becoming scarce. If we continue depleting them like this, we will be creating untold misery for urselves and for our future generations.



Plans for the Conservation of Nature

In 1992, Pakistan developed the National Conservation Strategy. The main objectives of the strategy are conservation of natural resources and improved efficiency in the use of resources. It also covers the policies for promoting efficiency and conservation of energy resources.

The Federal Ministry of Environment has launched the National Drinking Water and Sanitation Policy. It focuses on the provision of clean drinking water to entire population and the conservation of water resources. Water purification plants are being installed all over the country.

In 2006, the UNDP launched the project “Mass Awareness for Water Conservation and Management”. The objective of the project was to launch a comprehensive awareness campaign for the conservation and management of water resources in Pakistan.

The organization SCOPE (Society for Conservation and Protection of Environment) works with government for mass awareness and research for the conservation of natural resources in Pakistan.

The WWF (old name is World Wildlife Fund but now it is called World Wide Fund for Nature) is working on many projects related to the conservation of nature. The following are some important programmes of WWF-Pakistan (in collaboration with the government of Pakistan):

Programs of WWF-Pakistan:

  • Improving sub-watershed management and environmental awareness around Ayubia National Park
  • Plantation of the trees of Jatropha and Mangroves at District Thatta, Sindh
  • District-wise forest cover assessment of Pakistan
  • Saving Wetlands Sky High Programme (for the conservation and management of high altitude wetlands)
  • Indus Basin Water Security Project (to protect the water-flow needed for the maintenance of river ecosystem and for the benefit of nearby areas)
  • Regional Climate Risk Reduction in Himalayas.


Question 13: Write a note on dengue fever?

Answer: Dengue fever or break bone fever:

Dengue fever is a painful mosquito born infectious disease caused by dengue virus. It has become a major health problem in tropical and sub-tropical countries, including Pakistan. In Pakistan the first case of dengue fever was reported in the southern port city of Karachi in 1994. The province of Punjab particularly its capital, Lahore has seen a growing number of cases since 2007. According to recent report more than 3500 infected people live in Lahore city. In 2001 situation becomes alarming in Lahore city. According to world health organization, there are 50 million dengue infections worldwide every year. Now there are 2.5 billion people at risk from dengue fever.

Causative agent of dengue fever: Dengue fever is caused by dengue virus. There are four types of dengue viruses. Recovery from infection by one provides life long immunity against that virus but provides no protection against infection by the other three viruses.

Transmission of dengue virus: Dengue fever is transmitted through female mosquito Aedes aegypti. The female mosquito gets the virus when it bites an infected person. When infected mosquito bites another person viruses inter his/her blood and attack white blood cells.


Effects: When dengue virus inter the blood, it attacks white blood cells and destroy them. In severe cases the virus effects liver and bone marrow. This will result in decrease of blood platelets and patient suffer from bleeding. Sometime dengue fever converts into dengue haemorrhagic fever (DHF) or into dengue shock syndrome (DSF).

Symptoms of dengue fever: The sign appears (begin) 4 to 10 days after a person is bitten by mosquito. These include.

High fever up to 41 OC and chill.

severe headache

Muscles, bones and joint pains.

Widespread rashes on the body.

Pain behind eyes.

Nausea and vomiting.

Rarely, minor bleeding from gums or nose.

Dengue haemorrhagic fever DHF results in bleeding, low levels of blood platelets and blood plasma leakage.

In DSS (dengue shock syndrome) the blood pressure falls dangerously low.



Treatment, prevention and control of dengue fever: There is no vaccine or treatment for dengue fever. Use of analgesics, fluid replacement (Fluid replacement or fluid resuscitation is the medical practice of replenishing bodily fluid lost through sweating, bleeding, fluid shifts or other pathologic processes. Fluids can be replaced with oral rehydration therapy (drinking), intravenous therapy, rectally such as with a Murphy drip, or by hypodermoclysis, the direct injection of fluid into the subcutaneous tissue. Fluids administered by the oral and hypodermic routes are absorbed more slowly than those given intravenously) and bed rest is helpful for patient. Acetaminophen may be used to treat fever. Aspirin should be avoided because it promotes bleeding. Paracetamol is an effective drug. Oral re-hydration is helpful. Patient should increase fluid intake through fruit juices and ORS (Oral rehydration salt). The patient should use mosquito net so that the mosquito may not get virus from patient and may not transmit to other healthy peoples. Avoid traveling, so that virus cannot spread to other areas. The best method to control dengue virus and dengue fever is to check the spread of Aedes mosquito’s. Aedes aegypti breeds primarily in the containers used for water storage, discarded plastic bags, used automobiles tires and other items that collect water. The mosquitoes can be controlled through proper solid waste disposal and improve water storage practices. Small fish and crustaceans have also been used for killing the larvae of the mosquitos. Insecticide sprays have not proved efficient in killing the mosquitoes, because spray does not penetrate all habitat of adult mosquitoes.



Adult Aedes c Eggs of Aedes Larva of Aedes c Pupa of Aedes





  1. Explain what do you mean by the pyramids of number and biomass.

Answer: Please see answer of question no.5.


  1. Write a note on Carbon cycle.

Answer: Please see answer of question no.6.


  1. What are the different stages of Nitrogen cycle?

Answer: Please see answer of question no.7.


  1. Write notes on competition, predation and symbiosis.

Answer: Please see answer of question no.8.


  1. Explain how human activities have contributed to the loss of balance in nature.

Answer: Please see answer of question no.9.


  1. Write note on the causes and effects of the air and water pollutions.

Answer: Please see answer of question no.10.



  1. What are the different levels of ecological organization?

Answer: Please see answer of question no.2.



  1. Define ecosystem and its components.

Answer: Please see answer of question no.3.



  1. How the flow of energy is different from that of materials?

Answer:  Difference between flow of energy and flow of materials: The flow of energy in an ecosystem is unidirectional and is not cyclic while flow of materials or matter is cyclic.



  1. Define food chain and food web?

Answer: Food chainThe series of organisms in an ecosystem, in which an organism eats the preceding one and is eaten by the next one.

Food webA network of interconnected food chains; has a number of feeding connections amongst different organisms of a community.



  1. What do you mean by the concept of 3Rs with reference to the conservation of natural resources?

Answer: Please see answer of question no.12.



Terms to know.


Abiotic: The non-living components of the environment like water, sunlight, soil, heat etc.

Acid Rain: The rain containing sulphuric acid and nitric acid; with pH range of 3 to 6.

Ammonification: The decomposition of protein of dead plants and animals, and nitrogenous wastes to ammonia by ammonifying bacteria.

Atmospheric nitrogen fixation: The decomposition of protein of dead plants and animals, and nitrogenous wastes to ammonia by ammonifying bacteria.

Biogeochemical Cycle: The cyclic pathway through which chemical elements move from environment to organisms and back to the environment.

Biological nitrogen fixation: The conversion of gaseous nitrogen into nitrates by living organisms such as nitrogen fixing bacteria is called biological nitrogen fixation.

Biosphere: The last level of ecological organization; all the ecosystems of the world together form the biosphere.

Biotic: The living components of the environment; include producers, consumers and decomposers.

Carbon cycle: The biogeochemical cycle in which carbon flows between organisms and the environment.

Carnivore: The consumers which eat only animal flesh.

Commensalism: A type of symbiosis in which one of the partners gets benefit while the other is neither benefited nor harmed.

Competition: Type of interaction in which organisms compete for various needs like food, water and space with each other is called competition.

Consumer: The part of the biotic components of the ecosystem that consists of animals.

Decomposer: An organism which decomposes the dead bodies and dead matter.

Deforestation: Clearing of forests by natural causes or by humans.

Denitrification: The conversion of nitrites and nitrates into nitrogen gas.

Ecological pyramid: A representation of the number of individuals or amount of biomass or energy present in various trophic levels of a food chain.

Environment: The sum total of physical (abiotic) and biotic conditions which influence the organism.

Eutrophication: The enrichment of water with inorganic nutrients; the nutrients promote the growth of algae and it leads to increase in the number of the decomposers and depletion of oxygen.

Food chainThe series of organisms in an ecosystem, in which an organism eats the preceding one and is eaten by the next one.

Food webA network of interconnected food chains; has a number of feeding connections amongst different organisms of a community.

Global Warming: Increase in the temperature of the Earth; due to the addition of greenhouse gases in atmosphere, which do not allow solar radiations to reflect back into the space.

Interspecific interactions: Interactions between the members of the different species.

Intraspecific interactions: Interactions between the members of the same species.

Mutualism: (positive-positive interaction). In this type of symbiotic interaction, both partners (of different species) get benefit and neither is harmed.

Natural resources: The resources on Earth, which provide everything that humans use or consume.

Nitrification: The oxidation of ammonia to nitrites and nitrates by the nitrifying bacteria.

Nitrogen cycle: The flow of nitrogen between environment and the organisms.

Nitrogen fixation: Conversion of nitrogen into nitrates.

Non-renewable resources: A resource that is formed over very long periods; the rate of formation is extremely slow so cannot be replaced; e.g. minerals and fossil fuels.

Overpopulation: Increase in population beyond the carrying capacity of an area or environment.

Ozone: The O3 gas; also present in theupper layer of the atmosphere where it absorbs the ultraviolet rays present in the sun’s radiation.

Parasitism: A type of interspecific interaction in which smaller partner (parasite) derives food and shelter from the body of larger partner (host) and harms the host.

Phytoplankton: Photosynthetic organisms that float on the surface of water.

Pollutant: The substance that causes pollution.

Pollution: Any undesirable change in the physical, chemical or biological characteristics of air, water and land that may harmfully affect living organisms and other resources

Predation: An interaction between animals of two species or any plant and an animal, in which the predator attacks, kills and feeds on the smaller animal called prey.

Producer: An organism that produces organic compounds from inorganic compounds; an autotroph or plants.

Pyramid of biomass: The graphic representation of biomass present per unit area at different trophic levels in an ecosystem.

Pyramid of numbers: The graphic representation of the number of individuals per unit area at various trophic levels in an ecosystem.

Renewable resources: The resources which are replenished or reproduced easily e.g. sunlight, air, wind etc.

Symbiosis: Long or short term relationship between members of different species; three forms are parasitism, commensalism and mutualism.

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