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

Biology II for class X - Past Paper 2022

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Biology II
For class X
Past Paper 2022

Biology For Class X - Chapter No. 2 - Homeostasis - Question Answers

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CHAPTER 2: HOMEOSTASIS
Questions And Answers

Q.1: What is an internal environment of an organism?
Ans: Internal Environment of an Organism:
The internal conditions of an organism are referred as its internal environment; it includes H₂O quantity, different solutes, temperature, etc. For proper metabolic functions, the body requires all these conditions at a particular level.

Q.2: Why should the internal environment of living organisms remain constant? Give an example?
Ans: The internal conditions of an organism are referred as its internal environment; it includes H₂O quantity, different solutes, temperature, etc. The internal environment of organisms remain constant for proper metabolic functions; the body requires all these conditions at a particular level.
Lets take the example of temperature, the temperature of external environment is continuously change during day but the enzymes work within a certain range of temperature therefore, the living organisms maintain internal temperature within this range. Organisms maintain internal condition by feedback mechanism.


Q.3: Define homeostasis? What are the important aspects of homeostasis OR Briefly describe the adaptation of plants in different conditions?
Ans: Homeostasis:
Homeo means same and stasis means state or condition.
Homeostasis is set of metabolism which maintain internal environment of an organism within suitable limits.

Important Aspects of Homeostasis OR The Adaptation Of Plants In Different Conditions:
There are three important aspects of homeostasis.

• a. Osmoregulation:
  It is the maintenance of internal water and salt conditions by osmosis.
  
  
• b. Thermoregulation:
  It is the maintenance of temperature within suitable limits where enzymes can work properly (optimally).
  
  
• c. Excretion:
  It is the process where metabolic toxic waste or excess metabolic substances (i.e NH₃, urea or uric acid, gums, latex etc.) from body are removed.

Q.4: Define feedback system? Also draw a block diagram to show that how body maintains homeostasis by the feedback mechanism?
Ans: FEEDBACK SYSTEM:
The check and balance system in a body is called feedback system. In a feedback system three organs are involved.

1. Receptor:
   The organ which receive any change in the internal environment of the body. The  receptors transfer messages to CNS. e.g. 5 sense organs.
2. Central Nervous System:
   It is the major command and control center to which stimuli are reported by receptors and decisions are made and conveyed to effectors. Such as brain.
3. Effector:
   The central nervous system sends the message to a particular organ. Response is exhibited by these organs like muscles, glands etc., are termed as effectors.

Q.5: Describe excretion or storage of CO₂ in plants?
Ans: Excretion or Storage of CO₂ In Plants:
At daytime plant perform photosynthesis in green cells and respiration in all living cells. The CO₂ produced in respiration utilized in photosynthesis. When rate of photosynthesis will be higher than respiration the plant gets extra CO₂ from air and release extra O₂ in air through stomata.
At night plant only perform respiration only CO₂ is produced which is removed by the process of diffusion through body surface. The green parts perform these gases exchange through stomata while non green parts perform this gaseous exchange through body surface.

Q.6: Define Transpiration and Guttation OR Describe how extra water is removed from plants?
Ans: Removal Of Extra Water In Plants:
The plant store large amount of water this water can be removed from plant in two ways i.e.
(a) Transpiration
(b) Guttation

Transpiration:
It is the removal of water in the form of vapours from aerial part of plant. It occurs only at day time.
Plants modify their leaves size, structure and structure of stomata to control the rate of transpiration.

Guttation:
It is the removal of water in the form of liquid from the margin of leaves through special pores, hydathodes. It only occurs at night when water pressure is high in leaves and low temperature environment is present.

Q.7: Differentiate between transpiration and guttation.
Ans: Difference Between Transpiration And Guttation

S.NO.	Transpiration	Guttation
1.	It usually occurs during the day.	It usually occurs at night or early in the morning.
2.	Water is given out in the form of water vapours.	Water is given out in the form of a liquid.
3.	Several factors are responsible for this process.	This primarily occurs due to higher root pressure.
4.	Water comes out in the pure form.	Water droplets consist of various organic and inorganic salts dissolved in them. So it is not pure.
5.	It occurs through stomata, lenticels or cuticles.	It occurs through hydathodes only.
6.	It is a controlled phenomenon.	It is an uncontrolled phenomenon.

Q.8: How metabolic toxic waste or excess metabolic substances are removed from plant body?
Ans: Removal Of metabolic toxic waste:
Plants produce some secondary products like latex, resin and gum. These secondary products are insoluble, harmless compounds. Some plants produce special types of gums for example Neem or keeker etc. The extra amounts of these are removed from special pores called lenticels. The coniferous plants produce resins like material while the rubber plants produce latex which removes from scare like openings. Some of these carnivorous plants and okra produce mucilaginous material to capture insects.

Q.9: Describe types of plants on the basis of salt and water quantity in different conditions?
Ans: Types Of Plants:
The plants grow in different conditions of water and salts, on the basis of water and salt quantity there are four type of plants

1. Hydrophyte
2. Halophyte
3. Mesophyte
4. Xerophyte

Hydrophytes (hydro = water; phyta = plants):
The group of plants which grows in fresh water are called hydrophyte. They live completely or partially in fresh water so called totally or partially submerged plants. They adapt themselves for removal of excess water which can enter in this condition.

Characteristic of Hydrophyte

1. The plant do not have layer of cuticle.
2. These plants do not contain roots or poorly developed roots.
3. They have broad leaves if partially submerged and have stomata in the upper surface epidermis (to take part in transpiration) e.g. water lily.
4. They may have thin and spongy tissues in leaves and stem in totally submerged plant e.g. Hydrilla.
5. Examples are Hydrilla, Lotus, Lily plant

Halophytes (Halos= salt):
The group of plants which grows in sea marshes or salty water are called halophyte. In salty condition water moves outside the cell which is not suitable for plants. To move water from outside to inside the plant develop following characters.

Characteristic of Halophyte

1. They absorb water from the soil, which has higher salt concentration and low water potential.
2. They actively absorb salt into their roots.
3. Plants develop salt glands where plant store salts by taking it through active transport.
4. Plants oppose salt to move outside from vacuole.
5. Some salt accumulated at surface of leaf which attracts water from air.
6. Some halophytes absorb humidity by leave.
7. Examples are Glasswort, Cord grass

Mesophyte:
The group of plants which grows in well watered soil (or moderate water containing soil) are called Mesophyte.

Characteristics of Mesophyte:

1. They have developed root system which does not grow very deep.
2. Their body is covered by a layer called cuticle.
3. They contain stomata for evaporation of extra water.
4. They have moderate sized leaves.
5. Some Mesophyte excrete out water in the form of drops ( guttation)

Xerophytes:
The group of plants which grows in soil of low water quantity or in dry places are called Xerophyte. They grow in desert or steep slopes or at high altitude. To conserve water and absorb proper amount of H₂O they develop following characters.

Characteristic of Xerophyte:

1. They have vertically growing deep root system to absorb proper amount of water.
2. Some plant have horizontal root on the surface to absorb rain water rapidly.
3. They possess thick waxy cuticles over epidermis to conserve water.
4. They have short sized leaves or some plant leaves are modified into spine to prevent transpiration by reducing the number of stomata.
5. Some xerophytes has special parenchyma cells in stem, where they store water, this makes the stem soft, wet and juicy called succulent organs .g. cacti.
6. Examples are Cactus, Euphorbia.

Q.10: Discuss Osmoregulation in animals in detail.
Ans: Osmoregulation In Animals:
Animals live in aquatic and terrestrial habitat. According to their environment their cells require critical balance of water and solutes. Water continuously leaves and enters the cells with solutes to keep the water and solute in constant quantity to ensure smooth metabolic functions.

Osmoregulation in Aquatic Environment:
Concentration of salt in water defines the aquatic conditions. The water which contains very low amount of salt is called fresh water and the water which contains high salt is called marine water. Animals osmoregulate differently in both waters.

i. Osmoregulation in fresh water:
Fresh water animals have hypertonic conditions inside their body or cells so they are always facing the problem of flooding of H₂0 and loss of salts. These animals are further classified in two groups.

• Unicellular:
  * They pump out excess water by contractile vacuole.
  * E.g. Amoeba, Paramecium etc.
  
  
• Multicellular:
  * They pump out excess water by producing dilute urine.
  * Loss of salt is compensated by active uptake of salt by gills and skin as well as use of salt containing food.

ii. Osmoregulation in marine animals
Marine animals have mostly hypotonic conditions (low salt) inside the body but some of them develop hypertonic (high salt) or isotonic (same salt condition) by metabolism. These animals are further classified as:

• Bony Fish:
  * Have low salt inside the body.
  * Actively get sea water and have salt glands to increase the salt and desalination.
  * Produce concentrated urine.
  
  
• Cartilaginous Fish:
  * Have high salt by storing urea inside.
  * Eat food which contain nitrogenous compound i.e. meat.
  
  
• Osmoconformer:
  * Have equal amount of salt.
  * These animals do not require any activity to adjust their internal osmotic condition. i.e. unicellular.

iii. Osmoregulation in terrestrial condition:
In land animals excretion of water take place through body surface which leads to dehydration so they have developed number of strategies to maintain Osmoregulation.
Only arthropods, some molluscs, reptiles, birds and mammals can survive in this habitat because:

1. Their bodies are covered by exoskeleton or thick skin, which prevent loss of water.
2. They conserve water by reabsorption in kidneys and rectum.
3. Some of them can produce water from fats catabolism with the help of peroxisomes i.e. camel, kangaroos.
4. Continuously drinking of water or using liquid food.

Q.11: Define and explain Excretion? Also describe excretion in plants and animals?
Ans: Definition Of Excretion:
The removal of harmful substances produced in the metabolic process (nitrogenous metabolic waste) from the body is called Excretion.

Explanation:
During metabolism living organisms catabolize protein and other nitrogen containing compounds which produce some toxic nitrogenous compound. These toxic compounds are mainly NH₃ or urea or uric acid generally called nitrogenous waste. If these compound retain in the body and accumulate, they can damage the cells or organs therefore they must be removed from the body. The removal of these nitrogenous metabolic wastes is called excretion.

Excretion in Plant:
In plant rate of catabolic process is very slow and waste products are produced in less amount. They are used again in their anabolic process.
Plants are autotrophs, initially they produce carbohydrates as primary products. Carbohydrate is catabolized to produce CO₂ and H₂O. The CO₂ reutilized in photosynthesis and H₂O is not a toxic compound. As autotrophs they synthesize variety of compounds, so the waste products of one reaction are utilized in other metabolic reactions as reactant and consumed. Excess amount of waste materials is remove as:

• Excess water is removed by transpiration and guttation.
• Excess oxygen and carbon dioxide are removed through photosynthesis and respiration.
• Excess amount of ion are deposit into dead cell of plant body such as bark.

Excretion in Animal:
In animal removal of nitrogenous waste from the body is very essential. Animal have particular organ to excrete out nitrogenous waste. These organs are called excretory organs. There are different types of wastes in animals for which different excretory organs are used. The details are as follows:

Q.12: What are the main organs of human homeostasis system? OR Explain Homeostasis in man.
Ans: HOMEOSTASIS IN MAN
Humans has well developed homeostasis system. The main organs which involved in homeostasis are:

1. Skin
2. Lungs
3. Kidneys

(i) Skin:
The Skin is considered as the largest organ of the body, basically functions as a protective organ as the first line of defence but it also works efficiently as a homeostatic organ by maintaining temperature, water and salt.  It excretes water, salt, and urea from the body through sweat. 

(ii) Lungs:
Lungs are responsible for maintaining levels of O₂ and CO₂ in the blood, body fluid and cells in order to maintain the rate of respiration and continuous flow of energy.

(iii) Kidneys:
Kidneys are called filters of the body fluids, they maintain internal water by removing excessive water, also maintain urea, uric acids, creatinine and other waste by excreting them through urine.

Q.13: Explain the structure of Human skin in detail with labelled diagram?
Ans: STRUCTURE OF SKIN:
Human skin is consists of three layers ,namely:

• Epidermis,
• Dermis and
• Hypodermis.

Epidermis:

• Epidermis is the outer most layer which is made up of flat, dead cells containing keratin protein.
• This layer does not contain blood vessels.
• It is an impermeable to water and thus prevents water loss from the body.
• It also works as protective layer by preventing the entry of micro organisms.
• It also has sweat pores.
• Hairs are also emerge (come out) from epidermis.

Dermis:
Dermis is the layer present between epidermis and hypodermis, it contains many different structures i.e.:

• Dermis has nerves ending receptors to detect temperature change, pain, pressure etc.
• It also contains sweat glands which secrete sweat on the surface to maintain temperature and also secrete urea, water and salt.
• A network of arterioles is also present in the form of network, which are involved in temperature regulation.
• The dermis also contains hair follicle and sebaceous glands which secrete oily sebum.

Hypodermis:

• It is the inner most layer of skin.
• It contains fats which act as insulation against loss of heat.
• It also stores energy.

Q.14: Discuss the role of skin in regulating body temperature Or How skin works as thermoregulatory organ?
Role of Skin in Regulating Body Temperature OR Skin Works As Thermoregulatory Organ:
The skin is the organ which help in regulating body temperature .when the receptors in skin detects change in body temperature from set point (set point of human is 37 ℃) i.e. increase or decrease, and then Receptor send nerve impulse to brain. It occurs by feedback mechanism to correct the temperature.

In Hot condition If Body Temperature Start Rise: (Summer)

1. Production of sweat:
   The sweat gland starts to produce and secrete sweat. The sweat accumulates at the surface of skin and evaporates with heat energy so the body feeling cool.
   
   
2. Laying down of hairs:
   In hot condition, muscles which are attached with hair relax. It allows the hair to lie flat against surface of the skin.
   
   
3. Vasodilation:
   Arterioles found in the form of network in dermis, dilate (become wide) which increasing the flow of blood as well as it brings the blood vessels near the surface of skin which allows more heat loss. This process of vessel dilation is called vasodilation.

In Cold Condition When Body Temperature Starts Decreasing: (Winter)
In cold condition when the body temperature starts decreasing the skin maintains the temperature by following actions:

1. Erection of hairs:
   The muscles contract pulling the hairs upright and trapping a layer of insulating air next to skin. Now it is not very much effective in human.
   
   
2. Vasocontraction:
   Narrowing of blood arterioles of dermis occurs which reduces the blood flow in capillaries of skin so less heat is lost.
   
   
3. Decrease in sweat production:
   The sweat gland stops to produce and secrete sweat, so it prevent from energy loss.
   
   
4. Increase in metabolic rate:
   In cold conditions the rate of metabolism in the organs increases generating more heat which is distributed around the body in the blood stream. It prevents loss through the adipose tissue in hypodermic which work as an insulation layer.

Q.15: Explain and discuss the role of lungs to keep the CO₂ concentration low to certain level.
Ans: Role Of Lungs To Keep The CO₂ Concentration Low To Certain Level:
Lungs play a vital role in keeping the CO₂ concentration low to a certain level through the following steps:

1. Tissues / cells produce a large amount of CO₂ produced during the aerobic respiration. 
2. As blood passes through tissues via blood capillaries, this CO₂ diffused into the blood, where it reacts with water forms carbonic acid. This reaction takes place by an enzyme called carbonic anhydrase present in R.B.C.
3. The carbonic acid dissociate into H⁺ and bicarbonate ions. HCO₃^-1 ions.
4. The level of H⁺ in blood is continuously monitored by special detectors (receptor) carotid bodies and aortic bodies.
5. Most of the bicarbonate ions diffuse out from R.B.C to blood plasma.
6. A small amount of CO₂ is also carried and dissolved in R.B.C when the blood reaches lungs these bicarbonate ions diffuse back into RBC where again converted into carbonic acid then into CO₂.
7. The CO₂ diffuses out of the blood capillaries and into alveoli, from where it is expelled out when breathing out.
8. If the CO₂ level increases in blood, pH of blood start increasing so that the receptor send a message to the control centre which ultimately increase the breathing rate to expel out the CO ₂ efficiently.

Q.16: What is the role of the kidney in controlling blood composition?
Ans: Role Of The Kidney In Controlling Blood Composition:
Blood is the fluid having cells. In plasma, it contains a high amount of H₂O and some solutes like Na⁺, Cl^-, Ca⁺⁺, K⁺ etc. with nitrogenous waste. Liver continuously produces urea and NH₃ by breaking amino acid, we continuously take different solute ions in our food like Na⁺, Ca⁺⁺, K⁺ etc. the concentration of H₂O, solute and nitrogenous waste are maintained by kidney through process of filtration and reabsorption.

Q.17: What do you know about urinary system in man? OR Describe the urinary system of man with the help of diagram?
Ans: Urinary System In Man
Urinary system of man consist of:

1. A pair of kidney
2. A pair of ureters
3. A urinary bladder
4. A urethra

Kidneys:

• Kidneys are reddish-brown bean shaped organs, situated at the dorsal side of the abdominal cavity on either side of the vertebral column.
• The kidneys lie above the waistline.
• Each kidney has an area in the center of concave surface which faces the vertebral column; this area is called hillus.
• The renal artery, renal vein, nerve and ureter are connected to each kidney at the hillus.
• They are covered by a membrane are called peritoneum.

Ureter:

• The ureter is a narrow tube which connects the kidney to the urinary bladder.
• Urine passes through ureter to the urinary bladder.

Urinary Bladder:

• The urinary bladder is a thin walled muscular pear shaped bag situated towards the bottom of abdominal cavity in front of the rectum which stores urine.

Urethra:

• The urethra is a tube which comes out from the urinary bladder, runs down and opens outside the body through urinary opening (Anus).
• It passes urine from bladder to outside the body.

OR

Q.18: Explain the external an internal structure and function of kidneys in detail with labelled diagram.
Ans: External Structure Of Kidney:

• Kidneys are reddish-brown bean shaped organs, situated at the dorsal side of the abdominal cavity on either side of the vertebral column.
• The kidneys lie above the waistline.
• Each kidney has an area in the center of concave surface which faces the vertebral column; this area is called hillus.
• The renal artery, renal vein, nerve and ureter are connected to each kidney at the hillus.

Internal Structure Of Kidney:
The kidney is enclosed in a membrane called peritoneum. A fluid is filled between peritoneum and kidney called Peritoneal fluid which reduces the friction.

Parts of Kidney:
A longitudinal section (L.S) of kidney consist of three main parts:

1. The cortex
2. The Medulla and
3. The Pelvis

1. Cortex:

• Cortex is the outer dark brown portion.
• It is covered and protected by a fibrous capsule.

2. Medulla:

• The medulla is the inner lighter portion of the kidney.
• It contains many conical projection called renal pyramids. The human Kidneys contain 12-16 pyramids.
• It also contains nephron which is the basic functional unit of kidney.
• Nephrons are tiny kidney tubules where osmoregulation occurs to produce urine.
• The pyramids are connected to minor calyces (singular - calyx), which leads to major calyces.
• Major calyces open into pelvis, which leads to ureter.

3. Pelvis:

• Pelvis is the funnel like space.
• It is the enlarged portion of ureter inside the kidney.
• The kidneys are connected to the ureter at pelvis.

Functions Of Kidney:

• Kidney is an excretory organ. It removes excess mineral salts and nitrogenous waste products in the form of urine from the body.
• Kidney maintains osmoregulation and regulates water and salt balance in the blood.
• Kidneys make sure that the concentration of blood stays more or less constant.

OR

Q.19: Describe the structure of Nephron? OR Describe the structure of nephron within the L.S of kidney. And also draw labelled diagram of nephrons
Ans: Structure Of Nephron:
The structural and functional unit of kidney is called Nephron. Each kidney contains more than one million nephrons, which are microscopic urinary tubules.

Parts of Nephron:
Each nephron is sub-divided into four main parts:

1. Bowman's Capsule
2. Proximal convoluted tubule
3. Loop of Henle's
4. Distal convoluted tubule

1. Bowman's Capsule: 

• In each nephron inner end forms a cup-shaped swelling called Bowman's capsule.
• Each bowman's capsule have a ball of capillaries called glomerulus.
• Bowman's capsule with glomerulus are collectively called Malpighian body or Renal corpuscle.
  
  

2. Proximal Convoluted Tubule: 

• Bowman capsule leads into a short convoluted (coiled) tubule called Proximal Convoluted Tubule which passes into the medulla.
  
  

3. Loop of Henle: 

• The tubule enters into medulla, extends into renal pyramid and makes a U shaped structure called loop of Henle and it goes back into cortex.
  
  

4. Distal Convoluted Tubule:

• When tubule enters the cortex again, it becomes convoluted again.
  
• Function:
  At the distal convoluted tubule, some water and minerals salts are reabsorbed.

Collecting Tubules:

• Number of nephrons opens into a tube called collecting duct.
  
  

Network Of Blood Vessels:

• Nephrons are surrounded by different blood vessels that are connected to the renal artery and renal vein.

STRUCTURE OF NEPHRON

OR

Q.20: Describe the function of nephrons? OR Describe the network of blood vessels found in nephron and their functions?
Ans: Function Of Nephrons OR Network And Functions of Blood Vessels In Nephron:
Nephrons remove waste materials and excess water from blood and convert them into urine by the process of filtration, reabsorption, secretion and excretion. Nephrons are surrounded by different blood vessels that are connected to the renal artery and renal vein. The blood filter to produce urine in blood capillaries of nephrons as:

1. Afferent Arteriole:
   The renal artery when enters into kidney, it divides into millions of branches called afferent arteriole.
   Function: The blood enters the kidney through renal artery and goes into afferent arteriole.
   
   
2. Malpighian Body:
   Each afferent arteriole further divides into numerous blood capillaries in Bowman's capsule are collectively called glomerulus. The Bowman's capsule with glomerulus is called Malpighian body or renal corpuscles.
   Function: Ultrafiltration occurs at Malpighian body.
   
   
3. Efferent Arteriole:
   Blood leaving the glomerulus through efferent arteriole, enter in blood capillaries surrounding the nephrons.
   Function: these blood vessels carry away filtered blood from glomerulus.
   
   
4. Venule:
   Blood capillaries surround a loop of Henle's unite to form venule, which ultimately joins to form a branch of renal vein.
   Function: It carries filtered blood with less waste materials to the venous system.

Q.21: Draw labelled diagram of:

• Bowman's capsule and
• Section of kidney showing structure of two nephrons with blood supply.

Ans: 

BOWMAN'S CAPSULE

SECTION OF KIDNEY SHOWING STRUCTURE OF TWO NEPHRONS WITH BLOOD SUPPLY

OR

Q.22: Describe the role of Kidney in urine formation?
Ans: Role Of Kidney In Urine Formation:
Urine formation takes place in the following steps:

Urea formation:
The urea is formed with in the liver cells when the liver breaks down protein or amino acids, and ammonia.
The liver stores surplus glucose of food by converting it into glycogen and other food substances but it cannot store protein. The excess amino acids break and give some energy from it. The amino group (-NH₂) is removed from amino acid called deamination and is converted into ammonia (NH₃) which is very poisonous, it may kill the cell when stored in high concentration. So the liver cells quickly convert NH₃ into less toxic substance urea. This urea is carried by blood to kidneys and excreted out in the form of urine. A small amount of urea is also excreted in sweat as well.

Urine formation:
URINE:
The mixture of excessive mineral salts and nitrogenous waste products i.e. urea, creatinine and uric acid (which are poisonous if accumulated), These are removed from body with water. This mixture is called urine.
Urine formation takes place in the kidneys. The two main processes are involved in the formation of urine within nephrons, which are:

1. Filtration
2. Reabsorption

(i) Filtration:
The process of taking out materials from blood is called filtration . It is of two types:

• (a) Ultrafiltration
• (b) Selective filtration

(a) Ultrafiltration:
Ultrafiltration occurs at Malpighian body when the blood from afferent arteriole enter into glomerulus   located in Bowman's capsule. Most of the blood plasma is forced out of the glomerulus blood capillaries onto Bowman's capsule without any selection. This Process of non-selective filtration is called ultrafiltration.

(b) Selective filtration:
It occurs at proximal and distal convoluted tubules when blood flows into peritubular capillaries, the remaining amount of urea filters out from blood by active transport. It requires some energy.

(ii) Reabsorption:
In a normal adult about 120 cm³ of filtrate is formed in the kidney every minute. If this large amount of filtrate allowed to passing  out from the body as urine, the body will dehydrate and death may occur. To prevent this huge loss of water and useful salts, when the filtrate passes through the nephron useful substances and excessive water are reabsorbed in blood stream by:

• (a) Non-selective
• (b) Selective reabsorption

(a) Non-selective reabsorption:
It occurs at distal and proximal convoluted tubules without any selection.

• At the distal convoluted tubule, some water and minerals salts are reabsorbed.
• At proximal convoluted tubule, most the mineral salts and in a healthy person, all of the glucose and amino acids are reabsorbed through the walls of the tubules into the surrounding blood capillaries.  These solutes are absorbed via diffusion and active transport.
  This absorption is highly selective in quantity, and only those substances required by the body are reabsorbed readily.
  Most  of the eater in the filtrate is reabsorbed by osmosis here.

(b) Selective reabsorption:
It occurs at Loop of Henle's and collecting duct with the help of hormones. i.e. Antidiuretic hormone (ADH), Parathyroid hormones (PTH) and calcitonin.

• At the loop of Henle, some water is reabsorbed.
• At the collecting duct, some water is reabsorbed. Excess water, excess salts and metabolic waste products such as urea, uric acid and creatinine pass out of the collecting duct into renal pelvis as a mixture called urine.

Q.23: Describe the role of kidneys in osmoregulation?
Ans: Role of kidneys in osmoregulation:

• The maintenance of internal water and salt conditions of the body by osmosis is known as osmoregulation.
• The water potential (capacity to lose water) of blood in the body has to be kept constant because big and sudden change in the water potential of blood can lead to serious problems.
  e.g. if plasma becomes very much dilute water will enter the blood cells will swell and possibly burst.
• On the other hand if the blood plasma becomes too concentrated, water will move out of the cell by osmosis, as a result of it the blood cells and tissues will become dehydrated and shrink. This control of water and salt content of the body is known as osmoregulation.
• Kidney is not only an excretory organ; it also regulates water and salt balance in the blood. Kidney ensures that concentration of blood stays more or less constant.

Q.24: Describe different disorders of kidney and their treatment?
Ans: Kidney Problems Or Disease:
When the kidneys do not function properly due to different reasons this is referred as Kidney problem or Kidney disease.
There are many problems of kidney:

1. Kidney Stone
2. Kidney Failure

Kidney Stone
A kidney stone is a solid mass that forms from the crystals of calcium oxalate or Calcium Carbonate. Sometimes uric acid and cysteine are also present in it. These molecules separate from urine, precipitate in kidney and deposit in the form of stone. Sometimes these stones are not hard therefore they break into sand like crystals which can pass out of the body with urine without pain. The little large size stone however damages the kidney tissues; it may stuck anywhere in urinary tract and cause renal failure with pain.

Treatment:

1. Lithotripsy:
   If the size of stone is comparatively small we can use the technique of lithotripsy to break stone by ultrasonic waves (sound waves). The broken rudiments drain out from kidney with urine.
2. Renal surgery:
   The large size stone cannot be broken by lithotripsy, so it is removed only by the process of renal surgery.

Prevention:
The large intake of water is the only measure to minimize the chances of formation of stone in kidney.

Kidney failure:
Sometimes the nephrons of kidney are badly damaged and stop working due to certain reason or infection and the kidneys are not able to filter the harmful nitrogenous substance it is called Renal failure Or Kidney failure.
It is mainly due to solute dis-balance in blood and kidneys. The failure of kidneys allow urea and other waste materials to accumulate in blood. The amount of H₂O is not regulated also. This dis-balance of solutes causes death unless the patient is given treatment  to filter out wastes by machines.

Treatment of Kidney Failure:

1. Kidney Transplant:
   Patient of kidney failure may get a kidney transplant. In high degree renal failure the surgical transplantation of matching donor kidney is only the option left as the permanent treatment. A person with two healthy kidneys may donate one kidney and survive with one kidney.


2. Dialysis:
   Dialysis machine: A dialysis machine performs the function of a kidney. It helps to clean the patient's blood from metabolic waste products and toxic.
   If a donor is not available, the patient can be treated with dialysis using a dialysis machine. For effective treatment the patient needs to undergo dialysis 2-3 times a week. Each session lasts about 3-5 hours depending on the patient's body size and medical condition.

Q.25: Differentiate between:
(i) Thermoregulation in hot condition and thermoregulation in cold condition.
(ii) Vasodialtion and vasocontraction.
Ans: (i) Difference Between Thermoregulation In Hot Condition And Thermoregulation In Cold Condition

S.NO.	Thermoregulation In Hot Condition	Thermoregulation In Cold Condition
1.	In it body temperature rises.	In it body temperature falls.
2.	Sweat glands start producing and secreting sweats.	Sweat glands stop to produce and secrete sweats.
3.	Heat is lost to the environment.	Heat is retain.
4.	Vasodilation occurs i.e. blood vessels dialte resulting in the heat lost to the environment.	Vasocontraction occurs i.e. blood vessels contract resulting in the heat is conserved.
5.	Muscles attach with hairs are relaxed, causing laying down of hairs.	Muscles attach with hairs are contracted, pulling the hairs upright (erect).
6.	Metabolic rate is decreases.	Metabolic rate is increases.

(ii) Difference Between Vasodilation And Vasocontraction

S.NO.	Vasodilation	Vasocontraction
1.	When blood vessels (arterioles) in the dermis of skin dilates (become widen), it is called vasodilation.	When blood vessels (arterioles) in the dermis of skin contracts (become narrowed), it is called vasocontraction.
2.	This process occurs in hot condition (Summer).	This process occurs in cold condition (winter).
3.	In hot condition, body temperature start rises, which increases the flow of blood in capillaries near the skin.	In cold condition, body temperature start decreasing, which reduces the flow of blood in capillaries near the skin.
4.	Blood pressure inside the blood vessels decreases.	Blood pressure inside the blood vessels increases.
5.	It allows more heat loss to maintain thermoregualtion.	;It retain heat to maintain thermoregualtion.

Source: Special Thanks To Sir Syed Arif Ali