Biology For Class X - Chapter No. 7 - Man And His Environment - Question Answers

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CHAPTER 7: MAN AND HIS ENVIRONMENT
Questions Answer

By Mrs. Ayesha Arif
Vice Principal
(Jauhar Progressive School)

Q.1: Define Environmental Biology, ecology and habitat.
Ans: ENVIRONMENTAL BIOLOGY:
The scientific study of environment, ecology, evolution and global change within a combined form is called environmental biology.
It examines the ways where organism, species and communities influence and impacted by natural and human altered ecosystem.

ECOLOGY:
Ecology is the scientific study of different relationships with each other and with their nonliving environment which supports them.

HABITAT:
The area where an organism lives is called its habitat. It may be on land, in water or in the air.
For example: Habitat of frog is a pond.

Q.2: Describe the levels of ecological organization.
Ans: LEVELS OF ORGANIZATION OF ECOLOGY:
In ecology the level of organization ranged from organism to biosphere. These levels of study are:

1. Population
2. Community
3. Ecosystem
4. Biosphere
5. Biomes

1. Population:

• Definition: A group of organisms belongs to the same species lives and interacts in a particular area is known as population.
• Population mainly deals with factors that affect population size and composition.
• Example: A fresh water ponds includes a population of Hydrilla, a population of frogs, a population of deer family on land etc.

2. Community

• Definition: The next level of ecological organization is a community. The groups of populations or organisms (plants and animals) that lives in a particular area or habitat and belonging to different species which interact with each other is called community.
  Members of community interact with each other as well as with their nonliving environment.
• Example: A fresh water ponds includes a population of Hydrilla, a population of frogs, insects, worms, rohu and many other kinds of animals. All these organisms interact with each other and make a community.
  Similarly Population of deer and population of tiger live in forest and interact with each other and are members of same community.

3. Ecosystem:

• Definition: The term ‘ecosystem’ was first proposed by Tansley in 1935, where ‘Eco’ means the environment (house) and ‘System’ means an interacting area.
  Members of community interact with each other as well as with their nonliving (abiotic) environment. During this interaction energy is also transferred from one to another level. So the area where these all interactions occur called Ecosystem.
  In other words, an ecosystem is an area which is composed of organism interacting with each other and with the abiotic environment, as well as flow of energy occurs in a given area.
  It is higher level of ecological study and the basic structural and functional unit of ecology.
• Example: An ecosystem may be as small as dead truck tree, a puddle or as large as an ocean or forest.

4. Biosphere:

• Definition: Life is supported on earth within a thin envelope of air, water and soil. No life is exist beyond the earth's atmosphere o deep beneath its upper crust. Thus life sustaining envelope of earth is called biosphere. It is define as:
   "The largest possible major community comprised of all living organisms on earth is called Biosphere."
• Example: All ecosystems on earth combine and constitute the giant ecosystem, the biosphere.

5. Biomes:

• Definition: The biospheres may be divided into sub levels which are called biomes. Thus any bio-geographical region recognized by specific vegetation or climate called Biome.
• Example: Freshwater ponds, Grasslands, Marine, Desert etc.

Q.3: Define ecosystem and Name the components of ecosystem?.
Ans: ECOSYSTEM:
The term ‘ecosystem’ was first proposed by Tansley in 1935, where ‘Eco’ means the environment (house) and ‘System’ means an interacting area.
Definition:

"Members of community interact with each other as well as with their nonliving environment. During this interaction energy is also transferred from one to another level. So the area where these all interactions occur called Ecosystem."

In other words, "an ecosystem is an area which is composed of organism interacting with each other and with the abiotic environment, as well as flow of energy occurs in a given area."
It is higher level of ecological study and the basic structural and functional unit of ecology.
Example: An ecosystem may be as small as dead truck tree, a puddle or as large as an ocean or forest.

COMPONENTS OF ECOSYSTEM:
An ecosystem is made up of two types of components.

1. Non-living or Abiotic Components
2. Living or Biotic Components

ABIOTIC COMPONENTS OF ECOSYSTEM:
Abiotic or non living components of an ecosystem consists of physical aspects of its surroundings which influence upon the biotic components. Most important abiotic components are light, temperature, water, soil and air.

BIOTIC COMPONENTS OF AN ECOSYSTEM:
The living organisms which interact in an ecosystem are called biotic component. These living components include Producers, Consumers of all types and Decomposers.

Q.4: Describe abiotic components (factors) of an ecosystem?.
Ans: ABIOTIC COMPONENTS OF ECOSYSTEM:
Abiotic components of an ecosystem consists of Physical aspects of its surroundings which influence upon the biotic components. Abiotic components may control their distribution, reproduction, feeding, growth and metabolism. Many abiotic components affect an ecosystem.
Some important factors are:

• Light
• Temperature
• Water
• Soil and
• Air
  

All these work in interacting manner.
LIGHT:
It is the most vital factor, without it life cannot exist. It is a source of energy for every ecosystem.
Plants convert light energy into chemical energy by the process of photosynthesis. This chemical energy is stored in the form of food which is needed by every living thing.
Effect Of Light On Organism:
Light influence the ecosystem in many ways, directly or indirectly. Distribution of plants and animals is affected by:

• The type Or the quality (wavelength)
• Intensity of light,
• Exposure time or duration of light (photoperiod)

(i) Quality Or Type of Light:

• A small amount of light is utilized for photosynthesis i.e. out of seven colours of visible light; chlorophyll absorbs only red and blue light.
• Ultraviolet rays of light are harmful for life.
• Most of the light reaching the earth is converted to heat and thus it also maintains the temperature of the earth and atmosphere in the ecosystem.

(ii) Intensity of Light:

• Intensity of light controls plants growth. 
• It may destroy the chlorophyll.
• It also affects opening and closing of the stomata, permeability of the cell membrane, height and surface area of plant etc.
• In animals light affects development of pigments.

(iii) Exposure time of light (Photoperiod):

• Light is also necessary for vision.
• Duration of light (photoperiod) affects starts of certain biological processes e.g. flowering of certain plants, leaf fall and other aspects of plant growth.
• In animals biological rhythms such as reproductive cycles, sleep cycles, hibernation, migration, are affected by light duration.
• Making Vitamin D in human being.

2. Temperature:

• Another important abiotic factor affecting an ecosystem is temperature.
• It is low at high altitudes and high latitudes, the flora and faunas change accordingly.
• Temperature changes during day and night, also varies from season to season.
• Many birds and few mammals migrate or hibernate in winter.
• Enzyme activities of metabolic reactions are also altered with the changes in temperature.
• Most forms of life cannot survive during extreme temperature.

3. Water:

• All living things need water. It is the major part of protoplasm.
• It acts as the solvent for most of the compounds, raw materials of photosynthesis, inorganic substances enter in plants with water in dissolved form.
• The amount of water on land is controlled by rainfall and snowfall. The vegetation on earth is depended on the rate of rainfall. It means it also controls distribution of plants and animals on land.
• For example: Forest grows in the area which receives abundant rainfall whereas low rainfall in the area with extreme temperature develops desert conditions.

4. Soil:

• The upper layer of earth crust consists of particles of varying size and decomposed organic materials by microorganism called soil.
• The decomposed dead animals and plants are called humus.
• Humus enriches the soil and increases its water and air holding capacity.
• Plants are anchored in soil and depend on  it for their growth by absorbing water and inorganic substances.
• The type of soil and its fertility determines the flora and fauna in an ecosystem.

5. Air:

• Air is the gaseous envelope which surrounds the earth.
• It plays an important role in smooth running of ecosystem.
• Air is a mixture of N₂, O₂, CO₂ and H₂O vapours mainly.
• Nitrogen is essential constituent of protein. Oxygen is essential for respiration of all living organism. Carbon dioxide is the main requirement for photosynthesis to produce primary product i.e. carbohydrates.
• Humidity is the quantity of H₂O vapours in the air, which controls the rate of evaporation of H₂O vapours and transpiration in plants.
• The composition of air and its velocity controls other abiotic factors of environment which directly affect plant and animal life as well as the ecosystem as whole.

Q.5: Describe biotic components (factors) of an ecosystem.
Ans: BIOTIC COMPONENTS OF AN ECOSYSTEM:
The living organisms which interact in an ecosystem are called biotic component.
These living components include:

• Producers
• Consumers of all types and
• Decomposers.

1. Producers:
Producers always occupy the first trophic level in any food chain because only producers have the ability to trap and convert solar energy (sunlight) with the help of chlorophyll into food molecules by the process of photosynthesis.

• The producers produce food for themselves and other organisms of ecosystem.
• They are primary source of energy for other organisms.
• All members of community depend, directly or indirectly on the producers for their food and energy.
• Producers utilize a part of their food while consumers and decomposers utilize the remaining food.
• Example:
  Green plants and algae are the major producers. Some types of photosynthetic bacteria are also producers.

2. Consumers:
Animals and all other organisms which cannot make their own food are called consumers. They get energy and food from producers directly or indirectly.
Types Of Consumers:
On the basis of feeding level (trophic) mainly consumers are of three types:

1. Primary consumers:
   The consumers which directly feed on producers i.e. get energy and food directly from producers are called Primary consumers. They are basically herbivores.
   Example: A grasshopper or caterpillar feeding on leaves of plants is primary consumers.
   
   
2. Secondary consumers:
   The type of consumers which feed on primary consumers i.e. get energy and food from primary consumers are called secondary consumers. They are basically carnivores.
   Example: A bird is a secondary consumer gets its energy and food when it eats grasshopper or caterpillar.
   
   
3. Tertiary consumers:
   The organisms which eats the secondary consumers to get energy and food are called tertiary consumers and they are carnivores.
   Example: An eagle which eat the small bird, which has already eaten grasshopper.

3. Decomposers:
Microorganisms which break down complex food molecules of dead organisms are called decomposers.

• They recycle the nutrients because they return it by decomposing and converting the complex organic molecules into simple inorganic molecules.
• Example: They are generally bacteria and fungi.

Q.6: Explain the flow of energy in an ecosystem as a non-cyclic process. OR Describe pyramid of energy in an ecosystem.
Ans: ENERGY FLOW IN AN ECOSYSTEM AS A NON-CYCLIC PROCESS:
All the organisms in an ecosystem need energy to carry out their life activities to stay alive. Its primary source is solar energy which is coming through sun in the form of sunlight. During the process of energy flow in the ecosystem:

• The energy of sun is trapped by producers (phototrophs-green plants) and converted into energy rich organic food molecules in the process of photosynthesis.
• Part of this energy is transformed to the primary consumers (herbivores) when they eat producers (plants).
• Primary consumers (herbivores) when eaten up transfer this energy to secondary consumers which in turn form the meal of tertiary consumers.
• Hence the energy is transferred to next level, the tertiary consumers (carnivores). Thus the energy flow is unidirectional in nature.

TROPHIC LEVELS:
The steps of transfer of energy rich food are called trophic levels. The producers and consumers in the ecosystem can be arranged into different feeding groups and are known as trophic level or the feeding level.

• The producers (plants) represent the first trophic level.
• Herbivores (primary consumers) present the second trophic level.
• Primary carnivores (secondary consumers) represent the third trophic level.
• Top carnivores (tertiary consumers) represent the last level.

FOOD CHAIN:
The series of energy transfer from one trophic level to another is by eating or being eaten up is called food chain, represented by using arrows.

10% Of ENERGY TRANSFERRED:

"Only 10% of energy is transferred from one trophic level to the other; rest is lost into the atmosphere."

At each trophic level not all but a small amount of energy is transferred to the next level where it is stored as plant material or animal flesh. More than half of the energy is lost as heat.
A significant quantity is consumed at each level by the organism itself in carrying out its own functions like movement, respiration, reproduction etc. It is therefore, all the energy at each level never reaches the next level, only 10% of energy at each level transferred to next level.

PYRAMID OF ENERGY:
The reduction in the transfer of energy at various level in an ecosystem is expressed in the form of a pyramid called the pyramid of energy.

Q.7: Explain the flow f of materials in ecosystem as a cyclic process.
Ans: FLOW OF MATERIALS IN ECOSYSTEM AS A CYCLIC PROCESS:
In an ecosystem organic and inorganic materials flow in two ways, which are cyclic and interlinked with each other in some manner. These are:

1. Food chain and food web
2. Biogeochemical cycle

FOOD CHAIN AND FOOD WEB:
Food Chain:
Definition:

"The transfer of food material from producers through a series of organism i.e. producers to consumers with repeated eating and being eaten is called food chain."

Explanation:

• In ecosystem, the flow of food materials progress through food chain in which one steps follows another.
• Simple food chains occur rarely in ecosystem.

For example:
In Grassland ecosystem, The grass is eaten by grasshopper, locust and rabbit etc. These in turn is eaten by sparrows, lizards and jackals, respectively are secondary consumers. Sometimes these secondary consumers are eaten by hawk.

OR

Food Web:
Definition:
"In a given ecosystem various food chains are linked together and interact with each other to form a complete network called food web."
Explanation:

• In nature simple food chain occurs rarely. An organism drives its food from multiple sources and the same organism is eaten up by several organisms of higher trophic levels or an organism may feed upon several different kinds of organisms of lower trophic level.
• Food webs consist of many interconnected food chains and are more realistic representation of consumption relationships in ecosystems.

Q.8: Define biogeochemical cycle and write down its characteristics?
Ans: BIOGEOCHEMICAL CYCLES:
All elements in the earth are recycled. The growth and life processes of living organism require about 40 elements, among them six are needed in large quantities i.e. carbon, oxygen, hydrogen, nitrogen, phosphorous, and sulphur. These elements are taken up from environment by producers, made a part of protoplasm and finally returned back to environment. So,
Definition:

"The elements cycle continuously through organisms and environment are called Biogeochemical cycle."

Common Biogeochemical Cycles:
All biogeochemical cycles are closely interlinked with water cycle and energy flow in ecosystem. Following are some important biogeochemical cycles:

1. Carbon-Oxygen Cycle
2. Nitrogen Cycle

Carbon-Oxygen Cycle:
All the life in the earth is based on carbon. The carbon comes from carbon dioxide which is found in atmosphere. The respiration and photosynthesis help a lot to run the carbon-oxygen cycle. Respiration consumes oxygen for the combustion of food for release energy. During this process carbon dioxide is produced and released in the atmosphere. Photosynthesis on the other hand consumes CO₂ and release O₂.
Nitrogen Cycle:
The exchange of nitrogen between soil and atmosphere and its circulation through bodies of living organisms takes place through interrelated processes known as nitrogen cycle.

Characteristics Of Biogeochemical Cycles:
A biogeochemical Cycle has the following characteristics:

• Movement of nutrient elements from environment to organism and back to environment
• Involvement of biological processes
• A geochemical reservoir
• Chemical changes

Q.9: Describe carbon-oxygen cycle as biochemical cycle in detail?
Ans: Carbon-Oxygen Cycle:

• All the life in the earth is based on carbon. It is needed for the formation of proteins, carbohydrates, fats and many other substances that make up living things.
• The carbon comes from carbon dioxide which is found in atmosphere.
• Plant takes this CO₂ from air and converts it into carbohydrates by photosynthesis. Carbon in this form passes into a food chain.
• Animals get carbon by eating plants and animals. The amount of CO₂ in the air stays the same because it is returned to the air as fast as plants take it in.
• All living organism respires and thus exhale carbon dioxide.
• Decomposers set the CO₂ free from bodies of dead organisms. It is also returned to air by combustion that is burning of wood and other organic fuel like coal, petrol and gas etc.
• Two important processes, the respiration and photosynthesis help a lot to run the carbon-oxygen cycle.
  i) Respiration: Living organisms consume oxygen for the combustion of food for release energy. During this process carbon dioxide is produced and released in the atmosphere.
  ii) Photosynthesis: Plant takes this CO₂ from air and converts it into carbohydrates by photosynthesis and releases O₂. Carbon in this form passes into a food chain.
• Thus the balance is maintained.

Q.10: Describe nitrogen cycle as biochemical cycle in detail?
Ans: NITROGEN CYCLE:
Nitrogen is one of the important constituent of protein and DNA. It is therefore, an essential element in the structure of all living things. Plant use atmospheric nitrogen in the form of nitrates. Thus,
"The exchange of nitrogen between soil and atmosphere and its circulation through bodies of living organisms takes place through interrelated processes known as nitrogen cycle."
This cycle consist of three steps:

1. Nitrogen fixation
2. Nitrification
3. Denitrification

NITROGEN FIXATION:

"Conversion of atmospheric free nitrogen gas into soluble nitrogen compounds (nitrates) is called nitrogen fixation."

Nitrogen Fixation Occurs In Ecosystem:
The atmosphere contains about 78 percent nitrogen gas. It is an inert gas and the organisms cannot use it directly. Therefore, nitrogen is first changed to soluble nitrogen compounds such as nitrates (NO₃) which the plants can absorb from the soil.
Source of Nitrates: The following are the sources of nitrates for living organisms:

1. Nitrogen Fixation by Thunderstorm:
   The atmospheric Nitrogen combines with oxygen during lightning to make certain compound which ultimately form nitrates and reach to soil by rain water.
   
   
2. Nitrogen Fixation by Living Organism (Nitrogen Fixing Bacteria):
   The second source to fix atmospheric Nitrogen are three types of bacteria.
   * The first group lives in water are called cyanobacteria. They are photosynthetic.
   * Second group lives in soil.
   * Third group of bacteria lives in the roots of certain leguminous plants.
   These bacteria which help in nitrogen fixation are called nitrogen fixing bacteria.

NITRIFICATION:
Process where nitrogenous compounds of living organisms converts into nitrates is called Nitrification.
It is also performed by microorganisms that live in soil. These nitrates are reabsorbed by plants and the nitrogen cycle starts again. Protein of dead animals and plants, the excretory waste like ammonia, urea, uric acid are all nitrogenous wastes which are decomposed and the nitrates are recycled.

DENITRIFICATION:
The process of converting nitrogenous compounds into free nitrogen is called denitrification.

• It takes place by special bacteria which lives in anaerobic condition of soil. These bacteria called denitrifying bacteria.
• These bacteria break ammonia and nitrates back into free nitrogen, which is released in air so as to complete the cycle and to keep the nitrogen balance in nature.

Q.11: What do you know about ecological pyramids?
Ans: Ecological Pyramids:
An English ecologist Charles Elton develops the concept of ecological pyramids in 1927. The number of organisms in an ecosystem gradually decreases at each higher trophic level. He observed that the number of animals at low trophic level are abundant than the animals at high trophic level. Thus it is define as:
Definition:

"Presentation of number of individuals or amount of biomass or energy in various trophic levels from lower to higher level is called ecological pyramids."

TYPES OF PYRAMIDS:
Two pyramids are:
1. Pyramid Of Numbers:
Definition:

"Graphical representation of member of population in an area at different trophic levels is called pyramid of number."

It is an upright pyramid in an ecosystem. When number of organisms is counted at each level, it is observed that the producers are always more in number than other trophic levels and vice versa.

For example:

• The grasses sit at the lowest trophic level or at the base of the pyramid of number because of their abundance.
• The primary consumer, such as a grasshopper eats grass, and occupies the next higher trophic level. Grasshoppers are fewer in number than grass.
• The next trophic level is a primary carnivore, such as mice. There are fewer mice than grasshoppers because they consume grasshoppers.
• Secondary carnivores, such as snakes, occupy the next higher trophic level and feed on mice.
• Subsequently snakes are eaten by hawks, which occupy the highest trophic level and are least in number.
• This relationship is also expressed in the form of pyramid known as pyramid of number.

2. Pyramid Of Biomass:
Definition:

"The pyramid that shows the total mass of dry organic matter per unit area of organism at each trophic level. Such a pyramid is called pyramid of biomass."

It is drawn on the same pattern of pyramid of numbers and represents the total biomass. It shows that each higher feeding level contains less biomass than the previous trophic level. It results from energy loss in a food chain at each trophic level.

Q.12: What is interaction or relationship in the ecosystem? Describe its type?
Ans: INTERACTION OR RELATIONSHIP IN THE ECOSYSTEM:
In an ecosystem the living organisms develop number of relationship according to their needs. They not only interact with their physical environment but also with each other i.e. the herbivores develop their relation with producers, in the same manner carnivores depend on herbivores for their food. These associations maintain balance in growth and population. Such interactions take place between the two organisms by permanent or temporary association. It may be beneficial or harmful.
Positive Interactions:
Such interaction may be beneficial for only one without harming the other or for both the associates.
Negative Interactions:
Such interaction may be beneficial to one and harmful to the other.

TYPES OR RELATIONSHIP:
Some types of relationships are:

• Competition
• Predation
• Symbiosis

1. COMPETITION:
This type of a relationship is actually a cold war between the organisms of a community occupying the same habitat. This competition may be:
(a) Intraspecific Association:
i.e. between the members of same species. Intraspecific competition is mainly for mate, better shelter, better and high amount of food.
(b) Interspecific Associations:
i.e. between the members of different species. The interspecific competition is for food. This competition becomes a limiting factor because it ends in the survival of the fittest, and helps to keep the size of population and community in balance.

2. PREDATION:
A predator is an organisms which captures and kill the alive animal for its food. The animal being killed is called prey.
Predator relationship is an important factor in which one population continually determine the population of the other. Predator-prey relationship is an effective tool for biological control of the population of various organisms.
Example:Predators are either secondary or tertiary consumers in an ecosystem usually.
Some plants are also predators, these plants are called carnivorous plants i.e. Pitcher plant, Venus fly trap etc.

3. SYMBIOSIS:
It is an association between two living organisms of different species which live together. In this association either one is benefited while the other is harmed or at least one is benefited while the other is neither benefited nor harmed.

Types Of Symbiosis:
There are three types of symbiosis:

• Parasitism
• Commensalism
• Mutualism

i. Parasitism:

• Parasitism is a most common association. It is the interaction of organism called parasite which lives in or on the body of other organism called host.
• The parasite gets food from host.
• Sometimes the parasite gets place to live and thus benefited whereas its host is harmed.
• Parasites cause diseases; these disease causing parasites are viruses, bacteria, fungi, protozoa, insects, worms etc.
• A successful parasite takes just enough food from the host to grow and reproduce.
• They have rapid rate of reproduction.

ii. Commensalism:

• It is a type of symbiotic relationship in which one of the organism commensal, gets the benefit whereas the other is neither benefited nor harmed. 
• Example: A good example is spirochaete, a kind of spiral shaped bacteria, living between our teeth to obtain food but cause no harm to us.

iii. Mutualism:

• In mutualism two different kinds of organisms get benefit from living together.
• Usually they cannot live without each other because the two partners are dependent on each other for their survival and growth.
• Example is the nitrogen fixing bacteria, Rhizobium, live in the root (nodules) of leguminous plants. The bacteria get food from these plants while in return they fix gaseous nitrogen into nitrates for plant which is required for their growth.

Q.13: Define ecosystem balance
Ans: ECOSYSTEM BALANCE:
In an ecosystem living organism interact with other living organisms as well as with their abiotic factors. This interaction takes place by food chain, food web, energy cycle and biogeochemical cycle.

"The all interactions are important and help to keep the ecosystem balanced. This is called ecological balance. Ecological balance is a term that describes how ecosystem is organized in a state of stability where species exist with other species and environment."

Example:
A great example of ecological balance is the predator.
If prey population increases the number of predators will increase. When more predation will take place the prey population will be reduced. When prey population decreases the predator will come under stress ultimately their population will be reduced also. This predator-prey cycle therefore helps in maintaining the ecological balance.

Q.14: What is included in human environment?
Ans: HUMAN ENVIRONMENT:
The human environment is the earth we live on. It includes all the physical parts of earth such as air, soil, water minerals and its biological inhabitants such as animals, plants, bacteria and fungi etc.

Q.15: How does the human activity effects on ecosystem balance? Name and describe factors that effects ecosystem balance?
Ans: EFFECTS OF HUMAN ACTIVITY ON ECOSYSTEM BALANCE:
Ecosystem balance is disturbed by either natural disasters or by human activity.
The modern man, with all his technical development is exploiting natural resources at an alarming rate which is adversely damaging environment. These comforts have been achieved at the expense of healthy environment. Thus due to his numerous ecological disturbance, short sightedness and greedy exploitation of natural resources, he is confronted today with a number of serious environmental problems. These includes desertification of land due to erosion and deforestation, flooding, accumulation of waste and toxic substances in surroundings, pesticides, radio-isotopes accumulation, depletion of natural resources, spread of infection disease etc. All these upset delicate balance in ecosystem and environment as well.

MAJOR FACTORS THAT EFFECTS ON ECOSYSTEM BALANCE: are,

• Population growth
• Urbanization
• Global warming
• Deforestation and
• Acid rain

1. Population Growth:
Population growth is the increase in the number of humans on Earth.  There is a popular saying that all miseries lie in the three 'Ps' i.e. population, pollution and poverty, the last two are directly related to the first one.
Human population is growing exponentially. Dr Paul Ehlrich of Standford University regards this 'population explosion' as a 'population bomb' which is more dangerous than atom bomb.
The birth rate at present is 55 Million per year about 100 babies are born per minute.
Effects: This increase in population will create problems, such as:

• Shortage of food
• Shortage in health facilities and services.
• Starvation
• Epidemics
• Increasing poverty
• Increasing pollution in environment.

2. Urbanization:
The rapid increase in the population has generated a serious problem i.e. Urbanization. The people from rural areas migrate continuously to urban areas for better jobs, education and better standard of living. In 1947 urban population was 18%. Today it is more than 40%.
Effects: It effects are:

• Increase in number of katchi abadi in urban area.• Cause pollution of air, water and soil.
• Social evils also increase. These include drug abuse, looting, arson, kidnapping, dacoities, religious conflicts, ethnic clashes and linguistic riots.
• If birth rate and rapid growth of urban areas will not control than nature forcefully perform natural population controls by disease, feminine and war.

3. Global Warming Or Greenhouse Effect:
Due to excessive burning of fossil fuels, CO₂ and methane are produced which are generally called greenhouse gases. These gases, if produced in high quantity in atmosphere, they will accumulate below the ozone layer, which do not allow heat energy of sun to reflect back in space. As a result, heat remains within the earth’s atmosphere and increases the temperature. This phenomenon is called global warming or greenhouse effect.
Effects: The possible effects of global warming are:

• Due to global warming more evaporation of H₂O which ultimately reach to high rainfall.
• Melting of the polar ice and glaciers at high rate raises the sea level and ultimately reach to flood.
• Warming of atmosphere can cause heavy rains and strong hurricanes and storms.

4. Acid Rain:
Due to urbanization and industrialization more fuel burn, more acids are used in industries, as a result of these consumptions more CO₂, SO₂, NO₂ are liberated in air from their chimneys. When rain falls through these polluted airs H₂O react with these gases in air and produce carbonic acid, sulphuric acid and nitric acid respectively. These acids remain as vapours and condense into liquid when temperature falls. Such rain is called acid rain.
Effect:
The acid destroy soil, microorganisms of soil, skin of animals, building material.

5. Deforestation:
Forest are now being cut rapidly all over the world for fuel, fodder, timber, agriculture needs, river valley projects, industrial purposes, for construction of dams, roads, buildings etc. This process of cutting and destroying forests is called deforestation.
Effects: Deforestation result in:

• Recurrent floods
• Soil erosion
• Lowering of ground level
• Declination of annual rainfall
• Loss of fertility of the soil
• Reduction in wildlife
• Greater incidence of diseases because of loss of organism which helped in controlling the vectors.

Q.16: What is pollution? Describe its classification.
Ans: POLLUTION:
Literally pollution means "destruction of purity."
Scientifically pollution may be defined as:

"Any undesirable change in the physical, chemical or biological characteristics of environment (air, land, water and soil), which may or will harmfully affect human life, plants, animals or industrial processes, living conditions and cultural assets."

CLASSIFICATION OF POLLUTION:
Pollution is classified into two categories:
i) Material Pollution:
where some material or substance become excessive in environment; like air, water or soil pollution.

ii) Non-Material Pollution:
where material does not increase but environment disturb or become unbearable to live, i.e. noise, heat or radiation pollution.

Q.17: What are pollutants? Name some common pollutants.
Ans: POLLUTANTS:
All those substances that cause pollution called pollutants.

COMMON POLLUTANTS
Common pollutants are:

• Deposited matter such as soot, smoke, tar, dust and grit.
• Gases like SO₂, CO, CO₂, NO₂, CL₂ and O₃ etc.
• Chemical compounds like aldehyde, arsines, hydrogen flouride, chloro flouro methane, phosgene, detergents etc.
• Heavy metals like lead, mercury, iron, zinc etc.
• Economic poison like herbicide, fungicide, insecticide etc.
• Fertilizers.
• Sewage.
• Radioactive substances.
• Noise and heat.

Q.18: Explain air pollution its causes and effects. Also list the ways to control it. OR Describe different types of hazardous effects caused by air pollution.
Ans: AIR POLLUTION:
When amount of solid waste or concentration of gases other than oxygen increases in atmosphere it is called air or atmospheric pollution.

Causes:

• Automobiles
• Electrical power plant use coal, gas diesel or petrol.
• Industrial processes
• Heating and cooking plants
• Transport industry
• Industrial machines produce smoke, carbon monoxide (CO), carbon dioxide (CO₂), sulphur oxide (SO₂), nitrogen oxide (NO₂), chlorofluorocarbon (CFC) etc.

Effects: 
 Due to industrial toxic waste photochemical haze produces, as a result:

• Acid rain occurs.
• Greenhouse effects or global warming take place.
• Ozone depletion occurs.

CONTROL OF AIR POLLUTION:
Air pollution can be controlled by following ways:

• Use of proper filters:
  Industrial air pollutants should be passed through filters and other devices. So in this way particulates matter is removed before they release in air.
• Use of solar cooker:
  Industry should use solar cooker or bio-gas producing units.
• Environment friendly fuels:
  Use lead free fuels, Sulphur free fuels, use of CNG gases.
• Afforestation:
  Development of new forest or plantation. Forest use excessive CO₂, plants also absorb other air pollutants.

Q.19: What is meant by depletion of ozone layer?
Ans: OZONE LAYER:
In upper atmosphere a protective layer of ozone (O₃) gas is present which is very important for us because it checks the ultraviolet radiations from sun which are lethal for living organisms. This layer is called ozone layer.

DEPLETION OF OZONE LAYER:
Scientist have found ozone layer is gradually depleting (getting thin) due to chlorofluorocarbon (CFC), as they react with ozone and convert it into O₂. This process is called depletion of ozone layer.
Cause: The CFC used as propellant in pressurized aerosol, foaming agent, refrigerators etc. Each one atom of chlorine converts more than 100000 molecules of ozone O₃ to Oxygen O₂.

Q.20: Explain water pollution its causes and effects . Also list the ways to control it.
Ans: WATER POLLUTION:
Any contamination of fresh water or marine is called water pollution.

CAUSES:
The main cause of water pollution is human activity which pollutes streams, canals, lakes, rivers and seas. These pollutants affect the aquatic organism and quantity of water which directly and indirectly effect the life of human.
Sources: Major sources of water pollution are:

1. Organic Pollutants:
   Domestic sewage, agriculture run off, organic waste from breweries, bacteria, milk dairies, sugar mills, hotels etc.
2. Chemical Pollutants:
   Pesticides, insecticides, fungicides, herbicides, detergents, heavy metals, acid, mine waste, oil and oil dispersants, radioactive material etc.
3. Thermal Pollutants:
   Effluents from electric power plants or nuclear reactor plants.
4. Siltation:
   Deposition of soil and sand in the bottom of water reservoirs which raise the water levels and decrease water holding capacity. At last this silting cause floods.

EFFECTS:

• Contaminated water becomes unfit for consumption by humans and cattle.
• It results in drastic reduction of fish population.
• Water pollution results in increased cases of water borne diseases; like cholera, diarrhea, jaundice, etc.
• Eutrophication Or Algal Bloom:
  Algal bloom when floats on water surface:
  * They spoil fishing, swimming and recreational qualities of water.
  * These algal species when die not only add more organic matter to water but sometimes release toxins which have lethal effect to various organisms.
  * The excessive growth of other decomposers also use the excessive oxygen present in water which leads to the death of fishes and other organisms due to deficiency of oxygen.
  * It also reduces the light reaching to lower layer of water.

CONTROL OF WATER POLLUTION:

• Public awareness at all levels is important. It should be through social media, political leaders, institution from pre-primary level.
• Strict legislation and implementation is required on sewage treatment and industrial recycling processes.
• No industrial and agricultural waste should be added to water bodies before complete treatment.

Q.21: What is algal bloom and how it destroy the life of an aquatic ecosystem?
Ans: EUTROPHICATION OR ALGAL BLOOM:

"Growth of algae with very high rate due to increase in phosphorous and nitrogen compounds is called algal bloom or eutrophication."

Sewage water and agricultural field run off poses rich quantity of phosphorous and nitrogen containing compounds such as detergents. They accumulate in water reservoirs and promote algal growth upto dangerous level i.e. algal bloom.
Effects Of Algal Bloom On Aquatic life:
Algal bloom when floats on water surface:

• They spoil fishing, swimming and recreational qualities of water.
• These algal species when die not only add more organic matter to water but sometimes release toxins which have lethal effect to various organisms.
• The excessive growth of other decomposers also use the excessive oxygen present in water which leads to the death of fishes and other organisms due to deficiency of oxygen.
• It also reduces the light reaching to lower layer of water.

Q.21: Explain soil pollution its causes and effects . Also list the ways to control it.
Ans: SOIL POLLUTION:
Soil pollution is defined as the presence of toxic chemicals (pollutants or contaminants) in soil, in high enough concentrations to pose a risk to human health and the ecosystem.

CAUSES:
The pollution of soil has resulted from a number of human activities related to utilization of land resources.

• Mining, excavation of soil for bricks, cement making and construction of roads, dams, building etc.
• Dumping of solid waste in open space has reduced soil resources.
• Deforestation for building and industries.
• Over grazing by cattle of domestic use have destroyed the properties of soil.
• Excessive use of fertilizers, pesticides and poor drainage system.

EFFECTS:

• Pakistan is facing a massive problem of water logging and salinity due to improper canal system.
• Over grazing and deforestation leads to most serious problem of soil erosion by wind and water.
• In Pakistan, about 24 million area exposed to severe environmental threats, suffering from various kind of degradation.
• Eroded soil ultimately get in water bodies and cause problem of siltation.
• It alters soils biodiversity, reduces soil organic matter and soils capacity to act as a filter.
• It also contaminates the water stored in the soil and groundwater, and causes an imbalance of soil nutrients.

CONTROL:

• Recycling of solid waste.
• Proper dumping of solid waste.
• Plantation, development of forest.
• Development of pasture and meadows for grazing of animals.
• Proper irrigation system like drip system.

Q.22: What do you understand by the term conservation of nature?
Ans: CONSERVATION OF NATURE:
Conservation is a plan of avoiding the unnecessary use of natural materials or resources or a careful preservation and protection of natural resources by planned management to prevent exploitation of, destruction or negligence.

Q.23: What are natural resources? How many types of resources are there? How can we conserve them?
Ans: NATURAL RESOURCES:
Our environment is the source of all types of essential resources which are required to maintain our life on earth. Such resources are called natural resources. These resources are direct and indirect source of food, shelter, clothing, fuel, paper, luxury, beauty and recreation as well as wealth. 

TYPES OF RESOURCES:
There are basically two types of resources:

1. Renewable resources:
   The sources that can be used again and again are called renewable resources.
   e.g. Air, water, food, land, forest, live-stock, wildlife, are renewable.
2. Non- renewable resources:
   The resources that cannot be used again and again are called non-renewable resources.
   e.g. Petrol.

NEED TO CONSERVE RESOURCES:
The sources of earth are limited and are fast declining. It is therefore necessary to use these resources in a balanced and planned way.

• Overuse of renewable resources affect natural recycling process. Therefore, these natural resources should be conserved by the process of conservation.
• We can also conserve non-renewable resources. To do so we have to find alternative ways to slow down the dependency at one resource, just like petrol for automobiles or metals.
• We have to adopt the old principle of Reduce, Reuse and Recycle.
  Reduce means found ways to reduce the wastage like water usage and power usage.
  Reuse means to develop methods to reuse the resources again and again.
  Recycle means material like paper, glass, metal, plastic etc. can be recycled.

Q.24: State plans for conservation of nature in Pakistan?
Ans: PLANS FOR CONSERVATION OF NATURE IN PAKISTAN:

• Pakistan has diversified ecosystems therefore authorities developed different plans.
• National Parks 29
• Wild life Sanctuaries 69
• Game reserves 26
• Protected Wetlands 19
• Protected and reserved forest 07
• Marine protected areas
• Biosphere reserves (MAB) Lal suhanar Biosphere reserve Punjab,
• Ziarat Juniper forest, Pallas valley in Kohistan KPK.
• Pakistan National Biodiversity strategy and action plan 2015.
• Biodiversity Action plain by IUCN/ WWF/ World Bank, 1999.
• National Conservation Strategy plan, 1993.
• Wild life conservation project in Pakistan, 2007.
• Sustainable Forest Management UNDP in Pakistan. Project 2016-2020.
• Himalayan Jungle Project (HJP), 1991-1994.
• Palas Conservation and Development Project (PCDP) 1994
• Indus Dolphin Project (IDP), 1977
• Marine Turtle Conservation Project, 1980
• Kirthar National Park, Sindh
• Toghar Conservation Project (TCP), Balochistan, 1985
• Conservation of Chilghoza Forest and Associated Biodiversity of Suleiman Range, Balochistan, 1992
• Maintaining Biodiversity with Rural Community Development, 1999
• Mountain area Conservancy project (MACP), 1999
• Northern area Conservation Project (NACP), 2000
• Conservation of snow leopard in Northern Pakistan
• Conservation of Migratory birds in Chitral, NV/FP (KPK), 1992
• Himalayan Wild life Project (HWP), 1993
• Conservation of Chiltan Markhor in Hazarganji Chiltan National Park, Quetta.
• Protected areas Management Project
• Bear Baiting in Pakistan

Q.25: Nam some institution in Pakistan work for conversation?
Ans: INSTITUTIONS IN PAKISTAN WORK FOR CONSERVATION:

• Environment and climate change UNDP In Pakistan
• Society for Conservation and Protection of environment, SCOPE
• Environment and Natural Resource Management (National Rural Support program)
• Conservation in Pakistan
• National Energy Efficiency and Conservation Authority
• Environmental organization in Pakistan (Help save Pakistan's environment)
• Pakistan Environmental Protection and Resources Conservation Project.
• Pakistan Environmental protection Agency (PEPA)
• Himalayan Wild life Foundation (HWF)

Q.26: Name some endangered animals in Pakistan?
Ans: ENDANGERED MAMMALS OF PAKISTAN:

1. Punjab urial
2. Markhor
3. Snow leopard
4. Asia Sandspit Green Turtle
5. Indus River Dolphin
6. Bear Of Deosai

ENDANGERED BIRDS OF PAKISTAN:

1. Siberian Crane
2. Falcon
3. Cheer Pheasant
4. Chacor
5. Long billed vulture
6. Red Avadavar

Source: Special Thanks To Sir Syed Arif Ali