Chapter 16


Define ecology.
The study of the interrelationship between organisms and their environment is called ecology.
What is a species?
A species is a group of organisms which can interbreed freely in nature, to produce fertile offspring.

Q.3. What are the different levels of ecological organization?
Ans: In ecology, the levels of organization range from organism to biosphere.
Organism .
An organism is defined as an individual animal, plant, or single celled life form. An organism may be unicellular or multicellular.
A group of the organisms of the same species inhabiting a specific geographical area (habitat) at a particular time is called a population. ,
All the populations that live in a habitat and interact in various ways with one another are collectively called a community.
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.
Example: A pond, a lake, and a forest are examples of natural ecosystems. Ecosystems may also be artificial for example an aquarium.
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. ‘ x ‘
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. .

Q.4. Define ecosystem and its components.

Ans: Ecosystem
The self-sufficient unit of an environment that is formed as a result of interactions between its biofic community and the abiotic components is known as art ecosystem.
Components of Ecosystem
An ecosystem comprises of two basic parts i.e. abiotic components and “biotic components.
i) Abiotic .components: The abiotic components include the non-living factors present in ecosystem. The important non-living factors are light, air, water, soil and the basic elements and compounds.
ii) Biotic components: The biotic components comprise the living part (organisms) of the ecosystem. Biotic components are further classified as producers, consumers and decomposers. ,

Q. 5. Write an accbunt on biotic components of an ecosystem.
Ans: Biotic Components of an Ecosystem
The biotic components comprise the living part (organisms) of the ecosystem. Biotic components are further classified as producers, consumers and decomposers. Figure 16.1
i) 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 form the basis of any ecosystem. In terrestrial ecosystems, plants are the main producers. In aquatic ecosystems, the main producers are the floating photosynthetic organisms (mainly algae) called phytoplankton and shallow water rooted plants.
ii) 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.
Consumers are further classified as herbivores and carnivores.
(a) Primary consumers: Herbivores e.g. cattle, deer, rabbit, grasshopper etc. feed on plants. They are the primary consumers. They feed directly on plants or products of plants.
• (b) Secondary consumers: Carnivores feed on other animals. Primary carnivores (secondary consumers) feed on herbivores. Fox, frog, predatory birds, many fishes and snakes etc. are primary carnivores.

(c) Tertiary consumers: Secondary carnivores (tertiary consumers) feed on primary carnivores. Wolf and owl etc. are secondary carnivores. Tertiary carnivores e.g. lion, tiger etc. feed on secondary carnivores. Tertiary carnivores are not eaten by any other animals. They are also called top carnivores.
(d) Omnivores: Omnivores are the consumers that eat animal flesh as well as plants and plant products.
Ill) Decomposers: 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
Primary carnivore
Secondary carnivore
Tertiary carnivore
Herbivore Decomposers Figure 16.1 Producers, consumers, and decomposers in an ecosystem

Q. 6. How the flow of energy, is different from that of materials?
Ans: In an ecosystem, energy as well as materials travel from one trophic level to the next.

Figure 16.2 After death Body Activities Body Activities Body Activities Body Activities

Figure 16.2 Energy flow in an ecosystem

Trophic (food) level is the level at which an organism feeds in food chain. The first trophic level is made of producers; the second of primary consumers and so on.
Flow of Energy
The flow of energy in different trophic levels of ecosystem is .unidirectional. The following is an overview of the flow of energy in an ecosystem.
Primary source of energy: The Sun is the primary source of energy for all ecosystems. Producers get solar energy and transform it into chemical energy by the process of photosynthesis.
They store this energy in their tissues and also transform it into mechanical and heat energy during their metabolic activities.
The energy in producer’s tissues flows to herbivores when producers are eaten. He&ivores transform it into mechanical and heat eneVgy during their metabolic activities, use it for,their body activities and store the rest in their tissues.
Carnivores eat herbivores and get energy. They also use it for “their body activities and store thfr rest in their tissues. After the death of producers and consumers, theieihergy stored in their tissues is used by decomposers.
Law of Thermodynamics: 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 during transfer of energy at each trophic level.
Flow of Materials
The materials flow from one trophic level to the next by means of food chains and food webs.
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 16.3
Grass—* Grasshopper—* Sparrow -»Hawk
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 chains provide greater available energy and vice-versa.
Figure 16.3 A simple food chain

Food web: 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’. Food web can be defined as, “a network of food chains which are interconnected at various trophic levels” Figure 16.4

Figure 16.4 A food web in grassland ecosystem

Q.7. Explain ecological pyramids. What do you mean by the pyramids of number and biomass.
Ans: Ecological Pyramid 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.
Ecological pyramid can be defined as, “A representation of the number of individuals or amount of biomass or energy present in various trophic levels of a food chain”.

Ecological pyramids are of three types, (pyramid of numbers, pyramid of biomass, and pyramid of energy). Here, we will study two of them.
1. Pyramid of Numbers
It Is the graphic representation of the number of individuals per unit area at various trophic levels. Usually, producers are present in large number, primary consumers are in lesser number, and 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 Figure 165
Hawk (Tertiary consumer)
Sparrows (Secondary consumers)
Snails (Primary consumers)
Clover Leaves / (Producers)
2. Pyramid of Biomass
It is the graphic representation of biomass present per unit area at different trophic levels.” In a terrestrial ecosystem, the maximum biomass occurs in producers, and there is progressive decrease in biomass from lower to higher trophic levels. Figure 16.6

Q.8. Define biomass.
Ans: The total amount of living or organic matter in an ecosystem at any time is called “biomass”

Figure 16.5 Pyramid of numbers in an ecosystem


Q.9. What do you mean by biogeochemical cycles and what are nutrient cycles? Ans: Biogeochemical Cycles
Environment is the source of materials for all living organisms. Environment provides bioelements which are used by organisms for their bodies and metabolism. The materials are continuously recycled between organisms and environment. Biogeochemical cycles are the cyclic pathways through which materials move from environment to organisms and back to environment.
Since such moment of elements and inorganic compounds is essential for maintenance of life, they are also called ‘nutrient cycles’.

Q.10. Write a note on carbon cycle.
Ans:. Carbon cycle is a perfect cycle in the sense that carbon is returned to atmosphere as soon as it is removed.
Carbon atom is the principal building block of many kinds of bimolecular.
Source of Carbon: Carbon is found as graphite and diamond in nature. It also occurs as carbon dioxide in atmosphere.
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

Figure 16.7 Carbon cycle

Cycle of Carbon: 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 to herbivores, carnivores and decomposers.
Carbon dioxide is released back to environment by respiration of producers and consumers. It is also released by the decomposers. Burning of wood and fossil fuels also adds large amount of carbon dioxide atmosphere. Figure 16.7
Impact of human activities on carbon cycle: 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 green house effect and global warming.

Q.11. What are the different stages of nitrogen cycle?

Ans: Nitrogen Cycle Nitrogen is an important component of many biomolecules, like proteins and nucleic acids (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 utilized by plants. Nitrogen cycling involves several stages.
a) Formation of Nitrates
It is done in the following ways:
I) 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 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 as atmospheric nitrogen fixation.
• Some bacteria also have the ability to transform gaseous nitrogen into nitrates. Jt is called biological 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 nitrates. . r
It) Ammonlficatlon and Nitrification .
Ammonlf(cation 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 nitrates. It is called nitrification and is done by nitrifying bacteria. First, ammonia is converted into nitrates by bacteria (e.g. Nitosorfionas). The nitrates 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) Oenitrification
It is biological processes 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 Figure 16 8
Nitrogen in Atmosphere (N,)

Biological N-fixation by symbiotic bacteria
by denitrifying
by ammonifying
Biological N-fixation by free-living bacteria
Atmospheric N-fixation
– Nitrification by Nitrifying bacteria

Figure 16.8 Nitrogen cycle

Q.12. Differentiate between Intraspecific interactions and interspecific Interactions.
Ans: In all ecosystems, there are many kinds of interactions among living organisms. The interactions between the members of the same species are called Interspecific interactions while the interactions between trie members of different species are called interspecific interactions.

Q.13. Write a note on competition.
Ans: In ecosystems, the natural resources e.g. nutrients, space etc. are usually in short supply. So there is a competition among the organisms of ecosystem for the utilization of resources.
The competition may be intraspecific or interspecific.
Intraspecific competition is always stronger and more severe than the interspecific competition. Competition helps in maintaining a balance between the available resources and the number of individuals of a species.
Plants also show completion for space, light, water and minerals.

Q.14 What do you mean by predation? Give some examples. Ans. Predatlon
It is an interaction between two animals of different species or between a plant and an animal. In predation, one organism (the predator) attacks, kills and feeds on other organism (the prey).
Examples: Some examples of predation are given below:
• 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). , ‘
• Certain plants (Pitcher plant, sundew, Venus fly trap etc., are carnivorous and live as predators. 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.
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.

Q.15 What do you mean by symbiosis? What are its various types?
Ans. It is a relationship between members of different species, in which they live together for longer or shorter periods of time.
Types of symbiosis: Symbiosis is of three types: parasitism, mutualism, and commensalism
a) Parasitism
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.

Temporary parasitism: In temporary parasitism, the parasite spends most of its life cycle as independent free-living organism. Only a part of its life cycle is spent as a parasite. Leech, bed bug, mosquito are common temporary parasites of human.
Permanent parasitism: In permanent parasitism, the parasites spend their whole life cycle as parasites. Many disease causing bacteria and all viruses are permanent parasites.
Parasites may also be classified as ectoparasites and endoparasites.
Ectoparasites live outside i.e. on the surface of host’s body and get food from there. Mosquitoes leeches, lice etc. are the examples of ectoparasites.
Endoparasites live inside the body of host and get food and shelter. Bacteria, viruses, tapeworm, Ascaris, Entamoeba, Plasmodium etc. are the examples of endoparasites.
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.
b) Mutualism
In this type of symbiotic interaction, both partners (of different species) get benefit and neither is harmed.
1) Termites eat wood but are not able to digest it. A protozoan lives in their intestine. It secretes ‘cellulase’ enzyme to digest the cellulose of wood. In return, the termite provides food and shelter to the protozoan.
2) The nitrogen fixer bacteria RhizobiumHve 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 16.9,
c) Commenftalism
It is a type of symbiosis in which one partner is benefited while the other is neither benefited nor harmed.
Examples Figure’16.9 fiaderia in root
• Epiphytes are small plants found growing on nodules
other larger plants for space only. 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. In this way, the shark provides easy transport to the sucker fish to new feeding grounds.

Q.16. What type of symbiosis is present’between badgers and honey guide bird?
Ans: The honey guide bird feeds on wax and the larvae present in honey combs. 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 honey guide 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.

Q.17. What is IPCC?
Ans: 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 IPPC, Earth’s surface temperature has increased =0.2° C per decade in the past 30 years.

Q.18. What do you mean by greenhouse effect?

Ans: Greenhouse Effects 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 the Earth. Carbon dioxide, methane and nitrous oxide are important greenhouse gases. Since 1800, the amount of Carbon dioxide in atmosphere has increased about 30 %. The amount of methane has more than doubted and the amount of nitrous oxide has increased about 8%.

Q.19. Explain how human activities have contributed to the loss of balance in nature.
Ans: Ecosystem Balance and Human Impact The interactions among organisms and between organisms and the abiotic components of their environment produce steady and balanced ecosystems. Biogeochemical cycles also maintain the balance in ecosystems by recycling natural resources, so that they do not deplete. Humans try to modify environment (e.g. cutting of trees) to fulfill their needs. This has upset the delicate balance in ecosystems and nature as well.
Some of the human impacts on the balance of ecosystems and nature are as follows:
1. Global Warming
The addition of greenhouse gases (e.g. carbon dioxide, methane, ozone) in atmosphere increases -the temperature of the Earth. These gases remain in the lowest part of Earth’s atmosphere and do not allow solar radiations to reflect back into space, As a result, heat remains within the Earth’s atmosphere and increases its temperature. This is called global warming.

Effects of Global Warming
Due to global warming, polar ice-caps and glaciers’ are melting faster than the time taken for new ice layers to form. Sea water is also expanding causing sea levels to rise. Due to melting glaciers, rivers overflow and cause floods.
2. Acid Rain
When rain falls through air, it comes across chemicals such as oxides of sulphur and nitrogen. These chemicals interact with water vapours in the presence of sunlight to form sulphuric acid and nitric acid. These acids remain as vapours at high temperatures.
As temperature falls, the acids begin to condense into liquid form and mix with rain or snow, on the way down to the Earth. This makes rain acidic with pH range of 3 to 6.
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. It 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. Panics, 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.
3. Deforestation
Deforestation means clearing of forests by natural causes or humans. Large areas of forests have been cleaned for agriculture, factories, roads, rail tracks and mining. Humans cut trees for getting wood (lumber), which is then used for making structures and for heat production. 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.
4. Overpopulation
When the industrial revolution started some 250 years ago, 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.







The population of Pakistan
Pakistan population growth rate
5. Urbanization
Urbanization means growing of cities. People move from rural areas to cities in search of better jobs, education opportunities and higher standards of living.
Effects of Urbanization:
If there is rapid urban growth, 32-5
the governments find it difficult
to provide even the basic
facilities like health, education,
shelter, water, electricity etc.
Most of the migrants in cities
do not find good jobs and
become the part of urban poor.
There’ is overcrowding in
schools, hospitals etc. The
slum areas increased number Pakistan urban population (%age)
and people living there are at greater risk of diseases. Urbanization is a global problem and cannot be stopped but it can be managed. The current level of urbanization in Pakistan is about 32% which is not high by global standards.
A planned urbanization can solve many problems. 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. Utilizaiton of public transport instead of individual transports also proves effective way to manage urbanization.

Q.20. Define pollutants? What are major types of pollutants?
Ans: The substances that actually cause pollution are called the pollutants.
Examples: Pollutants may be the industrial effluents, domestic wastes, medical wastes etc.
Types: Pollutants are of two types i.e, i) Biodegradable, and ii) Non-biodegradable.

Q.21. Define pollution. What are the major causes of It?
Ans. 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.
For better life, human society is becoming more and more dependent on technology and industries. Technology and industry are making life easier and convenient for humans but are also contributing towards the pollution of environment.

Q.22. What Is noise pollution? What are its effects on health?
Ans: 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.

Q.23. Write a detail account on air pollution. Ans: Air Pollution
Air pollution is one of the major environmental issues of today.
It is defined as the change of composition of air by the addition of harmful substances (e.g. industrial and automobile gases and particulate matter).
Sources: All sources of air pollution are related to human activities. Burning of coal produces a lot of smoke and dust whereas burning of petroleum produces sulphur dioxide. In addition to these, air pollutants include carbon monoxide, carbon dioxide nitrogen oxides, hydrocarbons, particulate matter and traces of metals.
Different industries.produce air pollution in the following ways:
i) Fertilizer industries release oxides of sulphur and nitrogen, hydrocarbons, particulate matter and fluorine.
ii) Thermal industries are coal based and their pollutants are fly ash, soot and sulphur dioxide.
iii) Textile industries release cotton dust, nitrogen oxides, chlorine, smoke and sulphur dioxide. ‘
iv) Steel industries release carbon monoxide, carbon dioxide, sulphur dioxide, phenol, fluorine, cyanide, particulate matter etc.
Effects of Air Pollution
Studies show that global warming is one of the consequences of air pollution. Other effects of air pollution are as follows:

(a) 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.
(b) Acid rains: The air pollutants like sulphur dioxide and nitrogen oxides react-with water in the atmosphere producing acid rains.
(c) 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.
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:
a) 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.
b) Modification of Industrial Effluents: The air pollutants coming from industries should be passed through filters and other devices, so that the particular 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.
c) 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. .

Q.24. In which country the harmful effects of UV rays are visible?
Ans: 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.

Q.25. What is the expected estimated global temperature in next 100 years?
Ans. According to estimates, at the current rate of increase, the average global temperature will go up by 3°C to 8’C in the next 100 years.

Q.26. What threat Maldives is facing now a days? Ans. The Maldives’s Survival
Scientists fear that 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 meter above sea level. It is estimated that within 100 years, the Maldives might become uninhabitable and the citizens would be forced to evacuate.

Q.27. Write note on the causes and effects of water pollution. Ans. Water Pollution
It is the change in the composition of water by the addition of harmful substances. Water pollution severely affects the health of people.
i) 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 micro-organisms which spreads diseases.
ii) The wastes of industries (acids, alkalies, 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.
iii) Certain industries release a lot of hot water from their cooling plants. It results in heating up of water bodies and kills aquatic life.
iv) 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 can enter food chains. They cause a number of diseases in animals.
v) 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.
vi) Some heavy metals e.g. lead, mercury, arsenic and cadmium also make the water polluted. Such metals released from industrial and urban areas can be present in the water. If water with such heavy metals is given to plants, the metals enter the vegetables that grow on these plants. Such contaminated vegetables are harmful for human health. Heavy metals reduce growth and development, and cause cancer and nervous system damage. Mercury and lead can cause joint diseases such as rheumatoid arthritis, and diseases of kidneys, circulatory system and nervous system.
Effects of Water Pollution .-
The following are major effects of water pollution.
(a) Eutrophication: Enrichment of water with inorganic nutrients (nitrates and phosphates) is called eutrophication. The sewage and fertilizers contain large amounts 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 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.
(b) Food chain contamination: The non-biodegradable water pollutants may stay in water for long times. From water, they enter into small organisms, which are fed upon by fish, The fish in turn are consumed by land animals including human.
(c) Epidemics: Organic pollutants in water facilitate the growth of germs. Such polluted water causes epidemics like cholera, gastroenteritis etc.
Control of Water Pollution
i) Public should be made aware of the dangers of water pollution.
ii) Before releasing the sewage into water bodies, it must be purified through sewage treatment techniques. .
iii) Industrial wastes should also be treated before they are released into water bodies.

Q.28. Write an account on land pollution. Ans. Land Pollution
Land (soil) is an important resource as it is the basis for the growth of producers. In the recent times, soil has been subjected to pollution.
Sources of Land Pollution
i) The pesticides used” in agriculture have chemicals that stay in soil for long times, ii) The acid rains change the pH of soil making it unsuitable for cultivation.
iii) The household and other city garbage lies scattered in soil in the absence of a proper disposal system.
iv) Materials like polythene block the passage of water into soil and so decrease-the water- holding capacity of soil,
v) Many industries produce harmful chemicals which are disposed of without being treated.
vi) Improper disposal of nuclear wastes also cause radioactive substances to remain in soil for a long time,
vii) Open latrines in villages and some parts of cities are also the source of land pollution.
Control of Land Pollution
i) There should be suitable and safe disposal of wastes including nuclear wastes.
ii) Non-biodegradable materials like plastic, glass, metals etc. should be recovered and recycled.
iii) Inorganic pesticides should be replaced by organic pesticides.

Q.29. What do you mean by the concept of 3Rs with reference to the conservation of natural resources?
Ans. Conservation of Nature
Conservation of nature means the conservation of natural resources. Everything that we use or consume e.g. food, petrol etc. is obtained from natural resources. The renewable natural resources e.g. air are reproduced easily but the non-renewable resources (e.g. minerals and fossil fuels) are not replenished once they get depleted. We have to conserve the non-renewable resources because their reserves are limited and humans are heavily dependent on them for daily needs. The renewable resources too have to be judiciously used. 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. We should not waste water, electricity, fuel etc. We should turn off the tap when not in use. We should bathe with a bucket instead of shower. The lights and fans should be off, when we are not in room. We should take public transport (like buses) or walk short distances instead of using motor fuel. We should not waste food and should give unused food to poor people.
The R2: Reuse: We should Use a thing 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: Materials such as paper, plastic, glass etc. can be recycled. This decreases the volume of refuse and helps in the conservations of natural resources. For example, a recycling of one tone of paper can save 17 trees.
(We can add the R4 i.e. Reforest. Trees should be planted during the rainy season/Trees make our environment more cool, shady and green).

Q.30. What are the plans of government for the conservation of nature?

Ans: Plans for the Conservation of Nature
Following are the projects and plans of our government 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 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. ‘ ,
WWF( World Wide Fund)
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):

• 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 attitude wetlands),
• Indus Basin Water Security Project (to project the water-flow needed for the maintenance of river ecosystem and for the benefit of nearby areas),
• Regional Climate Risk Reduction in Himalayas.
Q.31. Write a note on Dengue fever.

Ans. Dengue Fever Dengue fever is a viral infection transmitted through a mosquito Aedes aegypti. It has become a major health problem in trophic and sub-trophic countries, including Pakistan.
There are four types of dengue virus. Recovery from infection by one provides lifelong immunity against that virus but provides no protection against infection by the other three virus types. ,
According to the World Health Organization, there are 50 million dengue infections worldwide every year. Now, there are 2.5 billion people at risk from dengue.
Mode of Action
The female Aedes mosquito gets the virus when it bites an infected person. When an infected mosquito bites another person, viruses enter his/her blood and attack white blood cells. Inside WBCs, viruses reproduce and destroy them. In severe cases, the virus affects liver and bone marrow. As a result there is a decrease in the production of blood platelets and patient suffers from bleeding.
The important symptoms of dengue fever is bleeding. Other symptoms of dengue include high fever, severe headache, .pain behind the eyes, muscles and joint pains and rash.

Sometimes, dengue fever converts into dengue hemorrhagic fever (DHF) or into dengue shock syndrome (DSS). DHF results in bleeding, low levels of blood platelets and blood plasma leakage. In DSS the blood pressure falls dangerously low.
Man and His Environment
Prevention and Cure
There is no vaccine or treatment for dengue fever. At present, the only method of controlling dengue virus transmission is to check the spread of Aedes mosquitoes. Aedes aegypti breeds primary in the containers used for water storage, discarded plastic containers, used automobile tyres and other items that collect rainwater. The mosquitoes can be controlled through following methods:
i) Proper solid waste disposal and improved water storage practices.
ii) Small fish and crustaceans have also been used for killing the larvae of the mosquito.
iii) Insecticide sprays have not proved efficient in killing the larvae of the mosquito.
iv) Insecticide sprays have not proved efficient in killing the mosquitoes, because spray does not penetrate all habitats of adult mosquitoes.
the correct option for the statements from the MCQs given
Encfrcle or tick below:
1. The study of the interrelationship between organisms and their environment is called (a) immunology (b) palaeontology (c) ecology (d) embryology
2. A group of organisms which can interbreed freely in nature to produce fertile offspring is called (a) population (b) community (c) individual (d) species
In ecology, the levels of organization range from organism to
(a) population (b) community (c) ecosystem (d) biosphere
A group of the organisms of the same species inhabiting a specific geographical area at a particular time is called a
(a) population (c) mutualism
(b) community (d) commensalism
A natural self-sufficient unit-comprising a biotic community and its abiotic environment is known as (a) mutualism (b) commensalism (c) ecosystem (d) competition
6. The light, water, air, and soil factors of environment are called
(a) abiotic factors
(b) biotic factors
(c) biological factors
(d) chemical factors
7. All populations that live arid interact in the same habitat make up (a) population (b) community (c) ecosystem (d) ecosphere
8. The thickness of biosphere is about (a) 20km (b) 25km (c) 30km (d) 40km
9. Which of these forms the basis of any ecosystem?
(a) bacteria (b) producers (c) consumers (d) decomposers
10. In terrestrial ecosystems the main producers are .
(a) algae
(b) rooted plants
(c) phytoplankton
(d) photosynthetic bacteria

tmwCtravan’s Biology^Objective
11. A community and environment constitute a (a) habitat (b) ecosystem (c) biosphere (d) food web
12. The largest ecosystem comprising all parts of the earth that support life is (a) ecosphere (b) biome (c) biosphere (d) habitat
13. The organisms which synthesize complex organic compounds (food) from inorganic raw materials are called
(a) consumers (b) predators (c) producers (d) decomposers
14. Most important producers in an aquatic ecosystem are
(a) fungi
(b) photosynthetic bacteria
(c) algae • • (d) all of these
15. Consumers may be
(a) herbivores
(b) omnivores
(c) carnivores
(d) all of these .

6 Which of these are principal decomposes of biosphere?
(a) bacteria and fungi
(b) bacteria and algae
(c) algae and fungi
(d) fungi and lichens
17 They break down the complex organic compounds of dead matter into simple compounds (a) omnivores (b) carnivores (c) predators (d) decomposers
‘•8. Light, temperature, air and water are examples of
(a) abiotic factors
(b) nutrients
(c) mineral resources
(d) biotic factors
its abiotic 19. The minerals released by decomposers are reused as nutrients by the
(a) fungi (b) bacteria (c) plants (d) algae
Energy from the sun enters an ecosystem through (a) producers (b) herbivores (c) omnivores (d) decomposers
that obtain their common source
The organisms energy from a constitute a
(a) food chain
(b) trophic level
(c) food web
(d) ecological pyramid
22. Which of the following is the sole point of entry for new energy into the ecosystem?
(a) producers (b) herbivores (c) carnivores (d) decomposers
23. Producers g,et solar energy and transfer it into
(a) mechanical energy
(b) physical energy
(c) chemical energy
(d) thermal energy
24! The storage and expenditure of energy in an ecosystem is in accordance with the basic law of
(a) mechanics
(b) segregation
(c) thermodynamics
(d) independent assortment
25. The materials flow from one trophic level to the next by means of
(a) food chain
(b) food web
(c) biogeochemical cycles
(d) both a and b

, Man and His Environment 149
26. A network of all the feeding relationships in an ecosystem is called
(a) food chain
(b) food web
(c) energy flow
(d) ecological pyramids
27. The flow of energy in an ecosystem is (a) cyclic (b) oneway (c) two way. (d) all of these
28. Who developed the concept of ecological pyramids?
(a) Charles Elton
(b) Charles Darwin
(c) Charles William
(d) Charles Candy
29. A representation of. the number of individuals or amount of biomass or energy present in various levels of a food chain with producers forming the base and carnivores forming the top is called
(a) trophic level
(b) food web
(c) ecological pyramid
(d) both a and b
30. How many types of ecological pyramids are present? (a) two (b) three (c) four (d) five
31. An ecological pyramid can show
(a) energy
(b) biomass
(c) number of organisms
(d) all of these
32. The pyramid xthat illustrate tptal amount of living matter at a tropical level is called
(a) pyramid of energy
(b) pyramids of biomass
(c) pyramid of number
(d) none of these
33. In a terrestrial ecosystem, the maximum biomass occurs in
(a) producers
(b) primary consumers
(c) secondary consumers
(d) decomposers
34. An ecological pyramid that indicates the energy contents in the biomass of a trophic level is
(a) pyramid of energy
(b) pyramid of biomass
(c) pyramid of numbers
(d) both a and b •
35. If you consider the earth as the size of an apple, then the biosphere will be as thick as the – (a) apple’s seeds
(b) apple’s puJp
(c) apple’s skin
(d) whole apple
36. Producers are known as
(a) autotrophs (b) heterotrophs (c) saprotrophs (d) decomposers
37. Tertiary consumer/s is/are (a) lion (b) rabbit (c) owl (d) grass hopper
38. Earth provides bioelements which are used by organisms for their bodies and
(a) food (b). metabolism (c) energy . (d) all of these
39. The cyclic pathway through which chemical elements move from environment to organisms and back to environment is called
(a) decomposition
(b) biogeochemical cycle
(c) food chain food web
(d) trophic level
150 Caravan’s Biology Objective
40. The principle building block of many kinds of bibmolecules is (a) phosphorus (b) calcium (c) carbon (d) nitrogen
41. In nature carbon is found as
(a) graphite
(b) diamond
(c) as carbon dioxide
(d) all of these
42. Carbon dioxide is released back to environment by respiration of
(a) producers
(b) consumers
(c) decomposers
(d) both a and b
43. Carbon dioxide is released back to the environment by
(a) decomposition of organic matter and dead bodies
(b) burning of wood and fossil fuels
(c) respiration of producers and consumers
(d) all of these
44. Major source of carbon for the living world is
(a) CO2 presents in atmosphere
(b) respiration of organisms
(c) carbonates of Earth’s crust
(d) all of these
45. The major process that brings carbon from atmosphere into living world is
(a) respiration
(b) photosynthesis
(c) decomposition
(d) all of these
46. Nitrogen is an important structural component of
(a) proteins and nucleic acid
(b) carbohydrates and nucleic acid
(c) lipids and carbohydrates
(d) lipids and proteins
47. Conversion of nitrogen into nitrates is .” called (a) nitrification (b) denitrjfication
(c) nitrogen fixation
(d) ammonification
48. Carbon dioxide is added to the carbon cycle by
(a) combustion of fuels
(b) weathering of rocks
(c) respiration (d) all of these
49. thunderstorms and lightening convert atmospheric nitrogen into
(a) nitric acid
(b) oxides of nitrogen
(c)’ ammonia (d) nitrous acid
50. Some living organisms have ability to transform gaseous nitrogen into nitrates. It is called
(a) atmospheric nitrogen fixation
(b) biological nitrogen fixation
(c) chemical nitrogen fixation
(d) biological denitrification
51. Which one of these are nitrogen fixers?
(a) Rhizobium
(b) Nostoc
(c) Azofobacfer and Clostridium
(d) all of these
52. These are free living nitrogen fixers (a) Rhizobium (b) Azofobacfer (c) Nostoc (d) both a and b
53. Ammonification is done by many species of
(a) Bacillus (b) Azofobacfer (c) Clostridium (d) Rhizobium
54. In nitrogen cycle, the nitrogenous wastes is converted to ammonia by
(a) assimilation
(b) nitrification
(c) ammonification
(d) both a and b

Man and His Environment 151
55. The conversion of ammonia to nitrates is carried out by nitrifying bacteria. This process is called
(a) ammonification
(b) nitrification
(c) nitrogen fixation
(d) assimilation
56. Reduction of nitrates to gaseous nitrogen fixation is called
(a) denitrification
(b) nitrification
(c) assimilation
(d) biological nitrogen fixation
57. Ammonia is converted into nitrates by bacteria
(a) Nitrobacter (b) Nitrosomonas (c) Clostridium (d) Rhizobium
58. The nitrites are converted into nitrates by
(a) Nitrobacter
(b) Nitrosomonas
(c) Pseudomonas
(d) Bacillus
59. Which one of these is denitrifying bacteria?
(a) Nitrobacter
(b) Nitrosomonas
(c) Pseudomonas
(d) Clostridium
60. Denitrification reduces soil fertility and is stimulated by
(a) water logging and poor drainage
(b) lack of aeration in soil
(c) accumulation of organic matter in soil
(d) all of these
61. Plants show competition for
(a) space and light
(b) water
(c) minerals
(d) all of these
62. The interactions between the members of the same species is called
(a) interaspecific interaction
(b) interspecific interaction
(c) predation
(d) mutualism
63. The interaction between the members of different species is called as
(a) intraspecific interaction
(b) interspecific interaction ‘(c) symbiosis (d) predation
64. Which one of these is always stronger and more severe
(a) intraspecific competition
(b) interspecific interaction
(c) mutualism
(d) commensalism
65. Which one of the following helps in maintaining a balance between the available resources and the number of individuals of a species (a) parasitism (b) commensalism (c) mutualism (d) competition
66. All carnivorous animals are (a) predators (b) prey (c) symbiont (d) parasites
67. Which one of the following is a carnivorous plant? (a) Delbergia (b) Srass/ca (c) sundew (d) both a and b
68. How many types of symbiotic ~* relationships are present? . (a) two (b) three (c) four (d) five
69. It is the long term relationship between members of different species (a) competition (b) predation (c) symbiosis (d) both a and b

152 Caravan’s Biology Objective
70. It is a type of interspecific interaction in which smaller partner derives food and shelter from the body of larger partner and harms them (a) predation • (b) parasitism
(c) eommensalism
(d) mutualism
71. Which one of these is an example of temporary parasitism?
(a) leech and mosquito
(b) bacteria and virus
(c) house fly and mosquito
(d) all of these
72. Which one of the following is, endoparasite? (a) ticks (b) lice (c) Ascaris (d) all of these
73. Which of these is a parasitic plant? (a) Cactu.s (b} Cuscuta (c) Pitcher plant (d) Venus fly trap
74. Parasitic plants, grow special types of roots into host tissues. These roots are known as •
(a) adventitious roots
(b) haustoria .
(c) secondary roots
(d) Cuscuta
75. In this type of symbiotic interaction, both partners get benefit and neither is harmed
(a) commensalism
(b) competition
(c) mutualism
(d) predation
76. In which of the followings ecological interdependence of organisms results?
(a) symbiosis
(b) host-parasite competition
(c) predator-prey relationship
(d) all of these
77. A relationship between organisms in which individuals of one species may kill and eat individuals of other species is called
(a) symbiosis (b) competition (c) predation (d) mutualism
78. An organism that hunts other organisms is called a ,(a) herbivore (b) consumer (c) predator (d) parasite
79. A parasite is adapted for living on or in the body of its (a) prey (b) predator (c) host (d) all of these *
80. Which of the following, is an example of a parasite?
(a) mites (b) Ascaris (c) lice (d) all of these
81. When two or more individuals attempt to use essential common resources, it results in
(a) mutualism (b) commensalism (c) competition (d) predator
82. Termites and Rhizobium are example of
(a) competition
(b) mutualism
(c) commensalism
(d) parasitism
83. The type of symbiosis in which one partner is benefited while the other is, neither- benefited nor harmed is called (a) mutualism (b) commensalism (c) predation (d) parasitism
84. They are small plants found growing on other plants for space only and absorb water and minerals from atmosphere and prepare their food.
(a) herbs (c) epiphytes
(b) weeds (d) grasses

Man and His Environment 153
85. Which of these produces a steady and balanced ecosystem?
(a) food chains
(b) biogeochemical cycles
(c) deforestation
(d) both a and b
86. The United Nations established Intergovernmental Panel on Climate Change (I PCC) in
(a) 1980 (b) 1985 (c) 1990 (d) 1992
87. According to I.PCC, global surface temperature has increased by 0.2°C per decade in the past (a) 20 years (b) 30 years (c) 35 years (d) 40 years
88. Which one of the following attaches to the surface, of sharks? (a) sucker fish (b) starfish (c) silver fish (d) cuttle fish
89. Which one of the following is greenhouse gas? (a) methane (b) nitrogen (c) sulphur (d) all of these
90. Scientists fear that the sea level is rising up to
(a) 0.3 cm/year (b) 0.6 cm/year (c) 0.9 cm/year (d) 1.2 cm/year
91. The pH of acid rain is in range of (a) 2 to 5 (b) 2 to 6 (c) 3 to 6 (d) 3 to 5
92. Large areas of forests have been cleaned for
(a) agriculture
(b) mining quarrying
(c) factories (d) all of these
93. The major effect of deforestation is
(a) flood and droughts
(b) landslides and toss of habitat
(c) landslides and soil erosions
(d) all of these
94. Some 250 years ago, the world population was at (a) 400 million (b) 500 million (c) 600 million (d) 800 million
95. In 2010, the population of Pakistan was
(a) 166,11,487 (b) 169,708,303 (c) 173,510,000 (d) 170,409,851
96. The growing of cities as people move from rural areas to cities is known as (a) urbanization (b) overpopulation (c) migration (d) deforestation-
97. The current level of urbanization in Pakistan is about (a) 28% (b) 30% (c) 32% (d) 36%
98. The substances that actually cause pollution are called the (a) wastes % “(b) pollutants (c) sewage (d) effluents
99. For better life, human society is becoming more and more dependent on
(a) technology (b) industries (c) urbanization (d) both a and b
100. An undesirable change in the physical, chemical or biological characteristics .of environment that may harmfully affect living organisms is called
(a) biodegradation
(b) pollution
(c) ozone depletion
(d) global warming
101. Pollution is affecting
(a) air (b) water (c) land (d) all of these
102. Unwanted, unpleasant-and annoying sounds are termed as
(a) noise ” (b) pop music (c) depression (d) hypertension

154 Caravan’s Biology Objective
103. The main effect of noise pollution results in
(a) hearing loss (b) depression (c) hypertension (d) all of these
104. Burning of petroleum produces (a) ammonia (b) nitrous oxide
(c) sulphur dioxide
(d) both a and b
105. Fertilizer industries produce oxides of (a) sulphur (b) nitrogen (c) phosphorus (d) both a and b
106. Thermal industries are coal based
and their pollutants are . (a) fly ash (b) soot
(c) sulphur dioxide
(d) all of •these
107. Cotton dust, nitrogen oxides, chlorine, smoke and sulphur dioxide are produced from
(a) thermal industries
(b) fertilizer industries
(c) textile industries
(d) burning of coal products
108. Steel plants produce which of the following pollutant?
(a) phenol, and cyanide
(b) hydrocarbons
(c) nitric acid
(d) soot and fly ash
109. According to estimates, at the current rate of increase, the average global temperature will go up by 3°c to 8 °c in the next
(a) 30 years (b) 50 years (c) 70 years (d) 100 years
110. In which country the rate of skin cancer is higher than the other regions of the world? (a) Australia (b) Egypt (c) China (d) India
111. The harmful effects of the UV rays are visible in
(a) Australia (b) New Zealand (c) South Africa (d) both a and b
112. Which one is the effect of air pollution?
(a) green house effect
(b) smog formation and ozone depletion
(c) acid rains (d) all these
113. When hydrocarbons and nitrogen oxides combine in the presence of sunlight, it results into
(a) smog formation
(b) greenhouse effect
(c) ozone depletion
(d) acid rains
114. Which one of the following causes respiratory disorders and allergies?
(a) green house effect
(b) smog formation
(c) ozone depletion
(d) acid rain
115. Which one of the following air pollutant destroy ozone molecule?
(a) carbon dioxide and phenol
(b) chlorofluorocarbons
(c) fluorine and cyanide
(d) all these
116. Ozone holes are created which permit UV rays to reach the Earth’s surface, which cause the (a) King cancer (b) allergies (c) skin cancer (d) all of these
117. The establishment of new forests by planting on non-forest areas is called (a) horticulture (b) afforestation (c) deforestation (d) apiculture
118. Which of the following environment friendly fuel/s?
(a) non-sulphur containing
(b) lead-free fuels

Man and His Environment 155
(c) phenol free fuels
(d) both a and b
(c) eutrophication
(d) both a and b
119. The effect of heavy metals on human 124. Which one of following blocks the
health is
(a) it reduces growth and development
(b) it causes cancer
(c) it causes nervous system damage
(d) all these
120. Exposure to mercury and lead can cause
(a) rheumatoid arthritis
(b) diseases of kidneys
(c) diseases of circulatory and nervous system
(d) all these
121. There are more than 200 tanneries operating in city of (a) Faisalabad (b) Sialkot (c) Kasur (d) Sheikhupura
122. Water tests of Kasur city showed that the drinking water is contaminated with
passage of water into soil and affects its water holding capacity?
(a) polythene
(b) glass and metals
(c) radioactive water
(d) /fertilizers
125. For the conservation of nature, we utilize the principle of(Rs= reuse, recycle, reduce etc), (a) 2Rs (b) 3Rs (c) 4Rs (d) 5Rs
126. A recovery of one tone of paper can save
(a) 12 trees (c) 17 trees
(b) 14 trees (d) 19 trees
(a) lead
(c) chromium
(b) mercury (d) all these
123. Enrichment of water with nutrients is called
(a) afforestation
(b) greenhouse effect
127. Pakistan implemented the National Conservation Strategy in (a) 1992 (b) 1996 (c) 2002 (d) 2006
128. Which organization works with government through mass awareness and research for the conservation of natural resources in Pakistan? (a) SCOPE (b) UNDP (c) WWF (d) UPGD

1. c
2. d
3. d
4. a
5. c
6. a
7. b
8. a

9. b
10. b
11. b
12. c
13. c
14. c
15. d
16. a

17. d
– 18. a
19. c
20. a
21. b
22. a
23. c
24. c

25. d
26. b
27. b
28. a
29. c
30. b
31. d
32. b

33. a
34. a
35. c
36. a
37. a
38. b
39. b
40. c

41. d
42. d
43. d
44. d
45. b
46. a •
47. c •
48. d

49. b
50. b
51. d
52. b
53. a
54. c
55. b
56. a

57. b
58. a
59. c
60. d
61. d
62. a
63. b
64. a

65. d
66. a
67. c
68. b
69. c
70. b
71. a
72. c

73. b
74. b .
75. c
76. d
77. c
78. c
79. c
80. d

81. c
82. b
83. b
84. c
85. d
86. c
87. b
88. a

89. a
90. c
91. c
92. d
93. d
94. c
95. c
96. a

97. c
98. b
99. d
100. b
101. d
102. a
103. d
104. c

105. d
106. d
107. c
108. a
109. d
110. a
111. d
112. d
156 Caravan’s Biology Ob/ecbVe
113. a 121. c
114. b 122. d
b 123. c
116. c 124. a
1. Which of the following is the abiotic component of the ecosystem? (a) producers (b) herbivores (c) carnivores (d) oxygen
2. When we eat onions, our trophic level is:
(a) primary consumer
(b) secondary vconsumer
(c) decomposer (d) producer
3. Identify the correctly matched pair:
(a) rainfall – biotic factors in ecosystem
(b) global warming-formation of fossil fuels ,
(c) renewable natural resource-air
(d) corn-secondary consumer
4. In the food chain tree -> caterpillar -» robin -» hawk -» coyote, which is the secondary consumer? (a) caterpillar (b) robin (c) hawk (d) coyote
5. In ecosystems, the flow of ———— is one way, while —-—— is/are constantly recycled.
(a) minerals, energy
(b) energy, minerals
(c) oxygen, energy
(d) glucose, water
6. In the food chain “grass -> rabbit -> fox-»bear -»mushroom”, how many types of decomposers are present? (a) 1 (b) 2 (c) 3 (d) 4
117. b 125. b
118. d 126. c
119. d 127. a
120. d 128. a
7. Organisms in the ecosystem that are responsible for the recycling of plant and animal wastes are: (a) producers (b) consumers (c) decomposers (d) competitors
8. Which form of Nitrogen is taken by the producers of the ecosystem? (a) nitrogen gas (b) ammonia (c) nitrites (d) nitrates
9. Dengue fever is a (a) viral (c) fungal
—^- fever (b) bacterial (d) protozoan
10. Virus of dengue fever is transmitted from a sick to healthy person by
(a) male Aedes mosquito
(b) female Aedes mosquito
(c) both male and female Aedes mosquitoes
(d) female Anopheles mosquito
11. Symptoms of dengue fever include
(a) high fever
(b) severe headache
(c) pain behind the eyes, muscles and joints
(d) all a, b, c
12. Dengue haemorrhagic fever results ir
(a) bleeding
(b) low levels of blood platelets
(c) blood plasma leakage
(d) alla.b, c
1.d 2. a 3. c “. 4. b 5. b 9.a 10. b 11. d 12 d
6. a
7. c
8, d

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