Question: What is pedigree analysis? Suggest how such an analysis, can be useful.

Summary:
Pedigree analysis is study of pedigree for the transmission of particular trait and finding the possibility of absence or presence of that trait in homozygous or heterozygous state in a particular individual. Pedigree analysis helps-
(i) in analysis of transmission of character in family over generation.
(ii) in genetic counselling of disease like haemophilia.
(iii) to identify whether a particular genetic disease is due to recessive gene or a dominant gene.
(iv) to identify the possible origin of the defective gene in the family or in a population.


Question: Mention any two autosomal genetic disorders with their symptoms.

Summary:
Sickle cell anaemia : Haemoglobin has less 02 transport, sickle shaped RBCs etc.
Phenylketonuria : Mental retardation (due to accumulation of phenylalanine in brain), hypopigmentation of skin & hair, eczema etc.


Question: Explain antibiotic, resistance observed in bacteria in light of Darwinian selection theory.

Summary: According to Darwin, environment selects organisms with favourable variations and these organisms are allowed to survive. When a bacterial population encounters a particular antibiotic, those sensitive to it die. But some bacteria having mutations become resistant to the antibiotic. Such resistant bacteria survive and multiply quickly as the competing bacteria have died. Some the resistance providing genes become widespread and entire bacterial population becomes resistant.


Question: Why did the superpowers have military alliances with smaller countries? Give three reasons.

Summary:
 Superpowers had military alliances with smaller states who were helpful for them in gaining access to:
1. Vital resources as oil and minerals.
2. Territory from where the superpowers could launch their weapons and troops.
3. Locations from where they could spy on each other.
4. Economic support to pay their military expenses.


Question: The Cold War produced an arms race as well as arms control. What were the reasons for both these development?

Summary:
The Cold War produced an arms race as well as arms control:
1. Cuban Missile Crisis engaged both of them (superpowers) in the development of nuclear weapons to influence the world.
2. US dropped nuclear bombs on the cities of Hiroshima and Nagasaki with the intention to stop Soviet Union from making military and political gains in Asia.
3. Both the powers were not ready to initiate a war because they knew that destruction from these will not justify any gain for them.
4. Both the powers were to be rational and responsible being restraint and avoiding risk of another World War to ensure human survival.
5. Hence, both the superpowers decided to limiting certain kinds of nuclear and non-nuclear weapons by signing various significant agreements within a decade i.e. Limited Test Ban Treaty, Nuclear Non-proliferation Treaty, Anti Ballistic Missile Treaty etc.


Question: Sometimes it is said that the Cold War was a simple struggle for power and that ideology had nothing to do with it. Do you agree with this? Give one example to support your position.

Summary:
Yes, the Cold War was a simple struggle for power and that ideology had nothing to do with it because:
1. The Cold War led to several shooting wars but this did not lead to another World War.
2. Despite direct confrontations in Korea (1950-53), Berlin (1958-62), the Congo (early 1960s), neither alliance system crossed certain limits.
3. Many lives have been lost in some of the arenas like Korea, Vietnam and Afghanistan but World War spread a nuclear war or global hostilities.


Question: What was India’s foreign policy towards the US and USSR during the Cold War era? Do you think that this policy helped India’s interests?

Summary:
 India’s foreign policy towards the US and USSR was two fold:
1. Took particular care in staging away from the two alliances.
2. Raised voice against the newly decolonised countries becoming part of these alliances.
3. Moreover, India tried to reduce the differences and rivalries between these alliances from escalating into a full scale war.
Yes, this policy served India’s interests also:
1. Non-alignment allowed India to take international decisions that served India’s interests rather than interests of superpowers and its allies.
2. India maintained a balance between two superpowers as if India felt ignored by one superpower it could tilt towards other superpowers.
3. Neither the alliance could take India for granted.


Question: For any substance, why does the temperature remain constant during the change of state?

Summary: During the change of state of any matter heat is supplied to the substance. The molecules of this matter use heat to overcome the force of attraction between the particles, at this period of time, temperature remains constant. This extra heat is acquired by the molecules in the form of hidden heat called latent heat to change from one state of matter to the other state.


Question: On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.

Summary: According to Thomson’s model of an atom, an atom consists of a positively charged sphere and the electrons are embedded in it. The negative and positive charges are equal in magnitude. So the atom is electrically neutral.


Question: What are the limitations of J.J. Thomson’s model of the atom?

Summary: According to J.J. Thomson’s model of an atom, the electrons are embedded all over in the positively charged spheres. But experiments done by other scientists showed that protons are present only in the centre of the atom and electrons are distributed around it.


Question: What are the limitations of Rutherford’s model of the atom?

Summary: According to Rutherford’s model of an atom the electrons are revolving in a circular orbit around the nucleus. Any such particle that revolves would undergo acceleration and radiate energy. The revolving electron would lose its energy and finally fall into the nucleus, the atom would be highly unstable. But we know that atoms are quite stable.


Question: How is prokaryotic cell different from a eukaryotic cell?

Summary: Prokaryotic cell is generally smaller in size (1-10 pm), nuclear region is poorly defined, the cell organelles are not membrane-bound and has a single chromosome. Eukaryotic cell is generally larger in size (5-100 pm), nuclear region is well defined with nuclear membrane. Membrane-bound cell organelles are present and has more than one chromosome.


Question: Explain, why is it difficult for a fireman to hold a hose, which ejects a large amount of water at a high velocity.

Summary: The water that is ejected out from the hose in the forward direction comes out with a large momentum and equal amount of momentum is developed in the hose in the opposite direction and hence the hose is pushed backward. It becomes difficult for a fireman to hold a hose which experiences this large momentum.


Question: How is our atmosphere different from the atmosphere on Venus and Mars?

Summary: Our atmosphere contains a mixture of many gases like nitrogen (78.08%), oxygen (20.95%), carbon dioxide (0.03%) and water vapor (in varying proportion). Whereas the atmosphere on Venus and Mars is mainly comprised of carbon dioxide. This carbon dioxide constitutes up to 95-97% of the atmosphere on Venus and Mars. It is supposed that due to this reason no life is known to exist on these planets.


Question: How does the atmosphere act as a blanket for our planet Earth?

Summary: It is a known fact that, air is a bad conductor of heat and our atmosphere contains mainly the air. Due to this reason, the atmosphere keeps the average temperature of the Earth fairly steady during the day and even during the course of the whole year. The atmosphere prevents the sudden increase in temperature during the daylight hours and during the night, it slows down the escape of heat into outer space.


Question: How are clouds formed in the atmosphere of the Earth?

Summary: The water evaporates due to heating up Of water bodies and other biological activities. The air also heats and rises. On rising, it expands and cools to form tiny droplets. These droplets grow bigger, expand and form clouds. The collection Of dust and other suspended particles facilitate the process.


Question: How do human activities lead to air pollution? What are some of the activities that do so?

Summary:
Human activities that would lead to air pollution are-
(i) Excessive use and burning of fossil fuels like coal and petroleum produces different oxides of nitrogen and sulphur. These are not only dangerous to our respiratory system but also leads to acid rain.
(ii) Incomplete combustion of various fuels forms unburnt carbon particles which lowers the visibility, especially in cold weather when water also condenses Out of air. This is known as smog and is a visible indication Of air pollution.
(iii) Large usage Of automobiles and improperly tuning of engines leads to the formation of carbon monoxide gas and Other oxides of nitrogen which causes lot of respiratory problems.
(iv) Forest fires, excessive mining and ore refining, excessive use of chlorofluorocarbons and excessive industrialisation leads to air pollution.


Question: Why do organisms need water?

Summary:
Organisms need water due to the following
(i) All cellular processes take place in a water medium.
(ii) All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.
(iii) Substances are also transported from one part of the body to the other in a dissolved form.
(iv) Water makes up about 70% of body weight Of all living organisms.
(v) It helps in the digestion of food and absorption of nutrients in the blood. Hence, organisms need to maintain the level of water within their bodies in order to stay alive. It helps in maintaining body temperature.


Question: What are the methods of preventing or reducing soil erosion?

Summary:
The methods of preventing soil erosion are :
(i) Afforestation : Forests reduce erosion as the roots of trees hold the soil in place.
(ii) Shelter belts : Trees planted in lines or hedges around farmland reduce erosion by reducing the speed of the wind.
(iii) Contour ploughing : Farmers plough land so that furrows lie across the natural slope of the land. These furrows trap water and do not allow it to flow down carrying the topsoil.
(iv) Terrace (or step) farming : A terraced hillside is less likely to be eroded than a natural hillside. Here a series of steps formed by horizontal strips supported by walls, catch the descending water. It gives the water sufficient time to percolate into the soil and nourish the crop.
(v) Soil cover : Soil left bare after harvesting a crop is often covered with dried vegetation to prevent erosion. Steep slopes that cannot be ploughed are covered with grass or pasture crops.
(vi) Preventing overgrazing : As the grass has a tendency to bind soil molecules, so even a very little grass on a field prevents erosion of soil. But if the grass is overgrazed, it exposes the soil to erosion.


Question: What are the different states in which water is found during the water cycle?

Summary:
All three possible states of water can be seen during the water cycle. These states are :
(i) Gaseous state (In the form Of water vapour which evaporates from the surface water). Liquid state (It is formed by the condensation of water vapour and can be Seen in the form of rain).
(ii) Solid state (It is formed by the freezing Of liquid droplets in the upper layer of atmosphere which can be seen in the form Of snow, hail Or sleet).


Question: The sun rises two hours earlier in Arunachal Pradesh as compared to Gujarat in the west but the watches show the same time. How does this happen?

Summary: From Gujarat to Arunachal Pradesh, there is a time lag of two hours, but the watches show the same time because the time along the Standard Meridian of India (82° 30’E) passing through Mirzapur in Uttar Pradesh is taken as the standard time for the whole country. Because the same standard time for the whole country has been adopted, the watches show the same time in Arunachal Pradesh, Gujarat, and in all parts of the country.


Question: How would you compare the east-flowing and the west-flowing rivers of the Peninsular plateau of India?

Summary:
East Flowing Rivers
The Mahanadi, the Godavari, the Krishna, and the Kaveri are the main east flowing rivers of Peninsular India. These rivers drain in the Bay of Bengal. These rivers make deltas at their mouth

West Flowing Rivers.
These rivers have a developed tributary system. Their tributaries are comparatively large in size. These rivers flow through not very deep channels. The Narmada and the Tapi are the main west-flowing rivers of Peninsular India. These rivers drain in the Arabian Sea. These rivers enter the sea through estuaries. These rivers are devoid of developed tributary system. Their tributaries are quite small in size. These rivers flow in a trough or a funnel-like narrow but deep channel.


Question: Why are rivers important for the country’s economy?

Summary: Rivers have been of fundamental importance throughout human history. Water from the rivers is a basic natural resource, essential for various human activities. Therefore, the riverbanks have attracted settlers from ancient times. These settlements have now become big cities. Make a list of cities in your state, which is located on the bank of a river. Using rivers for irrigation, navigation, hydropower generation is of special significance – particularly to a country like India, where agriculture is the major source of livelihood of the majority of its population.


Question: Why does India have a monsoon type of climate?

Summary: The monsoon type of climate is characterised by a distinct seasonal pattern. The weather conditions greatly change from one season to the other. These changes are particularly noticeable in the interior parts of the country. The coastal areas do not experience much variation in temperature though there is variation in rainfall patterns. Four main seasons can be identified in India – the cold-weather season, the hot weather season, the advancing monsoon, and the retreating monsoon with some regional variations.


Question: What are Jet streams and how do they affect the climate of India?

Summary: Jet streams are a narrow belt of high altitude (above 12,000 m) westerly winds in the troposphere. Their speed varies from about 110 km/h in summer to about 184 km/h in winter. A number of separate jet streams have been identified. The most constant is the mid-latitude and the subtropical jet stream. Over India, these jet streams blow south of the Himalayas, all through the year except in summer. The western cyclonic disturbances experienced in the north and northwestern parts of the country are brought in by this westerly flow. In summer, the subtropical westerly jet stream moves north of the Himalayas with the apparent movement of the sun. An easterly jet stream, called the tropical easterly jet stream blows over peninsular India, approximately over 14°N during the summer months.


Question: Why is the monsoon considered a unifying bond?

Summary: Despite great moderating influences on the climate of India, there are great variations in the temperature conditions. Nevertheless, the unifying influence of the monsoon on the Indian subcontinent is quite perceptible. The seasonal alteration of the wind systems and the associated weather conditions provide a rhythmic cycle of seasons.


Question: Why does the rainfall decrease from the east to the west in Northern India?

Summary:
The western coast and northeastern India receive over about 400 cm of rainfall annually. However, it is less than 60 cm in western Rajasthan and adjoining parts of Gujarat, Haryana, and Punjab. Rainfall is equally low in the interior of the Deccan plateau, and east of the Sahyadris. The third area of low precipitation is around Leh in Jammu and Kashmir. The rest of the country receives moderate rainfall.

Snowfall is restricted to the Himalayan region. Owing to the nature of monsoons, the annual rainfall is highly variable from year to year. Variability is high in the regions of low rainfall such as parts of Rajasthan, Gujarat and the leeward side of the Western Ghats. As such, while areas of high rainfall are liable to be affected by floods, areas of low rainfall are drought-prone.


Question: How is migration a determinant factor of population change?

Summary: Migration is the movement of people across regions and territories. Migration can be internal (within the country) or international (between the countries). Internal migration does not change the size of the population but influences the distribution of population within the nation. Migration plays a very significant role in changing the composition and distribution of a population.


Question: How do population growth and population change differ?

Summary:
Population growth
Growth of population refers to the change in the number of inhabitants of a country/territory during a specific period of time, say during the last ten years. Such a change can be expressed in two ways: in terms of absolute numbers and in terms of percentage change per year.
Population change
There are three main processes of change of population: birth rates, death rates, and migration. The natural increase of population is the difference between birth rates and death rates. The birth rate is the number of live births per thousand persons in a year. The death rate is the number of deaths per thousand persons in a year. The third component of population growth is migration. Migration is the movement of people across regions and territories. Migration can be internal (within the country) or international (between the countries). Internal migration does not change the size of the population but influences the distribution of population within the nation. Migration plays a very significant role in changing the composition and distribution of population


Question: What are the significant features of the National Population Policy 2000?

Summary:
The significant features of the National Population Policy 2000 are:
1. NPP 2000 identified adolescents as one of the major sections of the population that need greater attention.
2. Besides nutritional requirements, the policy puts greater emphasis on other important needs of adolescents including protection from unwanted pregnancies and sexually transmitted diseases (STD).
3. It called for programmes that aim towards encouraging delayed marriage and child-bearing, education of adolescents about the risks of unprotected sex, making contraceptive services accessible and affordable, providing food supplements, nutritional services, strengthening legal measures to prevent child marriage.


Question: Why are the wages for farm labourers in Palampur less than minimum wages?

Summary: A waged labourer might be employed on a daily basis, or for one particular farm activity like harvesting, or for the whole year. Most small farmers have to borrow money to arrange for the capital. They borrow from large farmers or the village moneylenders or the traders who supply various inputs for cultivation. The rate of interest on such loans is very high. They are put to great distress to repay the loan. Hence they pay very low wages to the farm labourers.


Question: What is the role of education in human capital formation?

Summary: Educated people find jobs in private firms while the uneducated people continue with the same work as their parents. They earn a meagre income like their parents, which is just enough to support a family. Several years of education adds to the quality of labour. This enhances their total productivity. Total productivity adds to the growth of the economy. This in turn pays an individual through salary or in some other form of his choice. It is a known fact that with investments made on education and health; one can yield a high return in the future in the form of higher earnings and greater contribution to society.


Question: What part does health play in the individual’s working life?

Summary: Health plays a very important role in an individual’s life because as we all know health is wealth and only a healthy person can work or perform to his full potential. An unhealthy person can not work efficiently. A healthy person is able to work harder and better, thus, earning more and living a better life. If the body is healthy, only then one can perform well. So, we can say that health plays a vital role in an individual’s life.


Question: Describe how the poverty line is estimated in India.

Summary:
A common method used to measure poverty is based on income or consumption levels. A person is considered poor if his or her income or consumption level falls below a given “minimum level” necessary to fulfill basic needs. While determining the poverty line in India, a minimum level of food requirement, clothing, footwear, fuel and light, educational and medical requirement, etc. are determined for subsistence. These physical quantities are multiplied by their prices in rupees. The resent formula for food requirements while estimating the poverty line is based on the desired calorie requirement.
As per 2000 figures; a family of five which is earning less than Rs. 1,640 per month is considered to be living below the poverty line. This figure is Rs. 2,270 per month for the urban area. The expected calorie intake has been fixed at 2400 calories per person in rural areas and 2100 calories in urban areas. A person consuming less than this amount is considered to be living below the poverty line.


Question: Do you think that the present methodology of poverty estimation is appropriate?

Summary: No, the present methodology of poverty estimation is not appropriate because it takes into account only the basic needs of food, clothing, fuel etc. But the quality of these basic necessities is the lowest quality available. The amount which is fixed as the poverty line does not include the margin for the constant price fluctuations. The poverty line should include some corrections for inflation and market fluctuations.


Question: What are the major reasons of poverty in India?

Summary: There were a number of causes for the widespread poverty in India. One historical reason is the low level of economic development under the British colonial administration. The low rate of growth persisted until the nineteen-eighties. This resulted in fewer job opportunities and a low growth rate of incomes. This was accompanied by a high growth rate of the population. The two combined to make the growth rate of per capita income very low. Another feature of high poverty rates has been the huge income inequalities. One of the major reasons for this is the unequal distribution of land and other resources. Despite many policies, we have not been able to tackle the issue in a meaningful manner.


Question: What are the strategies employed in order to remove poverty in India?

Summary:
Removal of poverty is one of the major objectives of the Indian developmental strategy. The current government strategy of poverty alleviation is based on two planks:
Promotion of Economic Growth and Targeted Anti-poverty Programmes
Some of the targeted anti-poverty programmes undertaken by the government are:
Prime Minister’s Rozgar Yojana (PMRY). This programme was started in 1993. It aims at creating self-employment opportunities for educated unemployed youth in rural areas and small towns.
Pradhan Mantri Gramodaya Yojana (PMGY). This programme was launched in 2000. It aims at creating and improving basic services like primary health, primary education, rural shelter, rural drinking water and rural electrification.
Rural Employment Generation Programme (REGP). This programme was launched in 1995. It aims at creating self-employment opportunities in rural areas and urban towns.
Mahatma Gandhi National Rural Employment Guarantee Act (MGNREGA). This act was passed in September 2005. The act provides 100 days assured employment every year to every rural household in 200 districts. Later, the scheme would be extended to 600 districts. One-third of the proposed jobs have been reserved for women.


Question: How has green revolution helped India, if at all?

Summary: After independence, India adopted a new strategy in agriculture, which resulted in the ‘Green Revolution’ especially in the production of wheat and rice. Indira Gandhi, the then Prime Minister of India, officially recorded the impressive strides of the Green revolution in agriculture by releasing a special stamp entitled ‘Wheat Revolution’ in July 1968. The success of wheat was later replicated in rice. The increase in food grains was, however, disproportionate. The highest rate of growth was achieved in Punjab and Haryana, where food grain production jumped from 7.23 million tonnes in 1964–65 to reach an all-time high of 30.33 million tonnes in 1995–96.


Question: Why is a buffer stock created by the government?

Summary: To ensure availability of food to all sections of the society the Indian government carefully designed a food security system, which is composed of two components: (a) buffer stock and (b) public distribution system. This is done to distribute foodgrains in the deficit areas and among the poorer strata of society at a price lower than the market price.


Question: How are seasonal hunger and chronic hunger different from each other?

Summary: Seasonal hunger is related to cycles of food growing and harvesting whereas chronic hunger is a consequence of diets persistently inadequate in terms of quantity or quality. People suffer from seasonal hunger in rural areas because of the seasonal nature of agricultural activities and because of causal labour in the urban areas whereas poor people suffer from chronic hunger because of very low income and thereby inability to buy food even for bare survival.


Question: What has our government done to provide food security to the poor? Discuss any two schemes launched by the government?

Summary: In order to help the poor, and provide food security to them,two special schemes were launched in 2000. They were Antyodaya Anna Yojana (AAY) and the Annapurna Scheme (APS) with special target groups of ‘poorest of the poor’ and ‘indigent senior citizens’, respectively. The functioning of these two schemes was linked with the existing network.


Question: What is a balanced chemical equation? Why should chemical equations be balanced?

Summary: An equation for a chemical reaction is an equation in which the number of atoms for each element in the reaction and the total charge is the same for both the reactants and the products. In other words, the mass and the charge are balanced on both sides of the reaction.


Question: While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Summary: While diluting an acid it is recommended that the acid should be added to water and not water to the acid because if water is added to concentrated acid to dilute it, then a large amount of heat is evolved at once. This heat changes some of the water to steam explosively which can splash the acid on one’s face or clothes and cause acid burns.


Question: Why does micelle formation take place when soap is added to water ? Will a micell be formed in other solvents such as ethanol also?

Summary:
Micelle formation takes place when soap is added to water because the hydrocarbon chains of soap molecules are hydrophobic (water repelling) which are insoluble in water, but the ionic ends of soap molecules are hydrophilic (water attracting) and hence soluble in water.
Such micelle formation will not be possible in other solvents like ethanol in which sodium salt of fatty acids do not dissolve.


Question: How do soaps clean our hands when we wash them with soaps?

Summary: When a dirty cloth is put in water containing dissolved soap, then the hydrocarbon end of the soap molecules in micelle attach to the oil or grease particles present on the surface of dirty cloth. In this way the soap micelle entraps the oily or greasy particles by using its hydrocarbon ends. The ionic ends of the soap molecules in the micelles, however, remain attached to water. When the dirty cloth is agitated in soap solution, the oily and greasy particles present on its surface and entrapped by soap micelles get dispersed in water due to which the soap water becomes dirty but the cloth gets cleaned. The cloth is cleaned thoroughly by rinsing in clean water a number of times.


Question: How could the modern periodic table remove various anomalies of Mendeleev’s periodic Table?

Summary:
(i) The modern periodic table is based on atomic number, while Mendeleev’s periodic table was based on atomic mass.
(ii) The isotopes of an element have same number of protons (or atomic number). So they are alloted the same position in modern periodic table.
(iii) Cobalt and nickel are placed at 9th and 10th position respectively.
(iv) Hydrogen has been alloted special position, i.e., it is placed at the top of alkali metals in the first group.


Question: How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?

Summary:
Modern periodic table is based on the atomic number and atomic number is directly related to the electronic configuration. One can find the group number and period number of an element on the basis of electronic configuration. For example, if an element has 1 or 2 electrons in its outermost shell, then it would belong to group 1 or group 2. And if it has 3 or more electrons in its outermost shell, then it would belong to group 10 4- the number of electrons in the outermost shell.

All the alkali metals have one electron in their outermost shell, so they are placed in group 1. Thus, all the group 2 elements have 2 electrons in their outermost shell. In group 15 elements, there are 5 electrons in their outermost shell. Similarly, the number of shells in an element indicates its period number. For example, the atomic number of magnesium is 12 and its electronic configuration is 2, 8, 2. Thus it is an element of 3rd period.


Question: What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Summary:
Aquatic organisms use oxygen dissolved in surrounding water. Since air dissolved in water has fairly low concentration of oxygen, the aquatic organisms have much faster rate of breathing.
Terrestrial organisms take oxygen from the oxygen-rich atmosphere through respiratory organs. Hence, they have much less breathing rate than aquatic organisms.


Question: What happens at the synapse between two neurons?

Summary: The small empty space between two nerve cells is called synapse. At synapse, a chemical substance is produced at the end of axon of one nerve cell that reaches to the other nerve cell through the dendrite. Thus, information is transmitted from one nerve cell to other nerve cell by synapse.


Question: What is the role of the brain in reflex action ?

Summary: There is no role of brain in reflex action. These involuntary actions are controlled by the spinal cord which take place immediately without thinking of how to respond to the stimuli.


Question: How do auxins promote the growth of a tendril around a support ?

Summary: When the tip of a tendril touches a support, then the auxins present in its tip move to that side of tip which is away from the support. Auxins promote growth. So, due to more auxins in it, the side of tendril away from the support grows faster (and becomes longer) than the side which is in contact with the support and makes the tendril twirl (or bend) around the support.


Question: How does chemical coordination take place in animals ?

Summary: Chemical coordination in animals takes place through the hormones secreted by the endocrine glands. Coordination in animals takes place through hormone system as well as nervous system which is called endocrine system. Endocrine glands secrete animal hormones directly into the blood that reach to the specific cells. Special type of molecules are present on the surface of cells to detect these hormones. These cells act according to the information that a particular hormone carries.


Question: How does our body respond when adrenaline is secreted into the blood?

Summary: The heart beat increases when adrenaline is secreted into the blood so that more oxygen is supplied to our muscles. The blood supply to the digestive system and skin decreases because the small arteries around the muscles of these organs contract. This turns the direction of blood towards our skeletal muscles. The breathing rate also increases due to the contractions of the diaphragm and rib muscles. All these responses enable us to face the situations of fear and anger.


Question: What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Summary: Receptors are specialised cells located in our sense organs like ear, nose, skin, tongue and eyes. The function of receptors is to detect information from the environment. For example, olfactory receptors detect smell. If receptors do not work properly, the information obtained from the environment will be delayed to reach the spinal cord or brain. In this situation, the response to the environmental stimulus will be delayed causing harm to the body. For example, if skin receptors are damaged, and one accidentally touches a hot object, then his/her hands might get burn as the damaged receptor cannot perceive the external stimuli of heat and pain.


Question: How does phototropism occur in plants?

Summary:
The movement in any part of a plant due to light is called phototropism. The shoot of plant shows positive phototropism and roots show negative phototropism.
Phototropism in plants occurs due to the hormone auxin. When light falls on one side of a plant, the secretion of auxin hormone is more in the part away from the light. Hence, auxin causes growth in length of the cells in shady part. So, the plant appears to bend towards light.


Question: Why do we prefer a convex mirror as a rear-view mirror in vehicles?

Summary:
We prefer a convex mirror as a rear-view mirror in vehicles because of two reasons :
A convex mirror always produces an erect image of the objects.
The image formed in a convex mirror is highly diminished or much smaller than the object, due to which a convex mirror gives a wide field of view of the traffic behind. A convex mirror enables the driver to view such larger area of the traffic behind him.


Question: A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

Summary: The light ray bends towards the normal. When a ray of light travels from an optically rarer medium to an optically denser medium, it gets bent towards the normal. Since water is optically denser than air, a ray of light travelling from air into the water will bend towards the normal.


Question: Why do stars twinkle? And explain why planets don't

Summary: Stars appear to twinkle due to atmospheric refraction. The light of star after the entry of light in earth’s atmosphere undergoes refraction continuously till it reaches the surface of the earth. Stars are far away. So, they are the point source of light. As the path of light coming from stars keep changing, thus the apparent position of stars keep changing and amount of light from stars entering the eye keeps twinkling. Due to which a star sometimes appear bright and sometimes dim, which is the effect of twinkling. The planets are much nearer to the earth than stars and because of this they can be considered as large source of light. If a planet is considered to be a collection of a very large number of point sources of light, then the average value of change in the amount of light entering the eye from all point size light sources is zero. Due to this the effect of twinkling is nullified.


Question: Why does the sun appear reddish early in the morning?

Summary: The light coming from the sun passes through various denser layers of air in the earth’s atmosphere before reaching our eyes near the horizon. Most of the part of blue light and light of small wavelength gets scattered by dust particles near the horizon. So, the light reaching our eyes is of large wavelength. Due to this the sun appears reddish at the time of sunrise and sunset.


Question: Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?

Summary: The current will flow more easily through a thick wire than a thin wire of the same material. Larger the area of cross-section of a conductor, more is the ease with which the electrons can move through the conductor. Therefore, smaller is the resistance of the conductor.


Question: What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?

Summary:
Advantages of connecting electrical devices in parallel with the battery are:
In parallel circuits, if an electrical appliance stops working due to some defect, then all other appliances keep working normally.
In parallel circuits, each electrical appliance has its own switch due to which it can be turned on turned off independently, without affecting other appliances.
In parallel circuits, each electrical appliance gets the same voltage (220 V) as that of the power supply line.
In the parallel connection of electrical appliances, the overall resistance of the household circuit is reduced due to which the current from the power supply is high.


Question: What are the disadvantages of using fossil fuels?

Summary:
(i) The burning of fossil fuels produces large amount of carbon dioxide that causes increased greenhouse effect.
(ii) The burning of fossil fuels (such as coal) produces smoke which pollutes the air.
(iii) The burning of fossil fuels produces acidic gases such as sulphur dioxide and nitrogen oxide. These acidic gases cause acid rain that affects our water and soil resources.
(iv) Fossil fuels cannot be replenished in short time because it takes millions of years to form them.


Question: What is geothermal energy?

Summary: Energy stored as heat in certain regions of the earth (called hot spots) is called geothermal energy. Hot spots are the locations below earth’s crust where upward moving magma gets collected due to geological changes. When underground water comes in contact with the hot spots, steam is generated. This steam is utilised to generate electricity using pipes and turbines. Sometimes hot water from the hot spot finds outlet at the surface. Such outlets are called hot springs.


Question: What are the advantages of nuclear energy?

Summary:
The advantages of nuclear energy are that :
It produces a large amount of useful energy from a very small amount of a nuclear fuel (like uranium-235).
Once the nuclear fuel (like uranium-235) is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. There is no need for putting in nuclear fuel again and again.
It does not produce gases like carbon dioxide which contributes to greenhouse effect or sulphur dioxide which causes acid rain.


Question: Why are some substances biodegradable and some non-biodegradable?

Summary: The microorganism like bacteria and other decomposer organisms (called saprophytes) present in our environment are specific in their action. They break down the materials or products made from natural materials (say, paper) but do not break down man-made materials such as plastics. So, it is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable, whereas others are non-biodegradable.


Question: What are some ways in which non-biodegradable substances affect our environment?

Summary:
(i) Biodegradable substances are decomposed by the action of microorganisms and decomposed materials are recycled through geo-chemical cycle.
(ii) These substances keep the environment clean.


Question: What is ozone and how does it affect any ecosystem?

Summary: Ozone is an isotope of oxygen, i.e., it is a molecule formed by three atoms of oxygen. At the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiations from the sun. These radiations are highly damaging to organisms. Ultraviolet rays can cause skin cancer.


Question: Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?

Summary: Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example, on removing producers; herbivores would not be able to survive or they would migrate and ecosystem would collapse. If herbivores are removed, producers would grow unchecked and carnivores would not get food. If carnivores are removed, herbivores would increase to unsustainable levels and could destroy the producers. If decomposers are removed, the dead animals would pile up due to which the environment would become polluted. In addition to this, if dead animals will not decompose, the recycling of nutrients in the soil will be stopped and its fertility will be reduced. As a result the green cover of the earth will be lost. Thus to maintain the balance of the ecosystem the presence of organisms is necessary at each trophic level.


Question: Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Summary:
The damage to the ozone layer is a cause for concern because if the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiations coming from the sun would reach the earth. These ultraviolet radiations would cause skin cancer and other ailments in men and animals and also damage the plants.
In an attempt to protect the ozone layer, the United Nations Environment Programme (UNEP) unanimously forged an agreement among its member countries to freeze CFC production at 1986 levels.


Question: What would be the advantages of exploiting resources with short term aims? How would these advantages differ from the advantages of using a long term perspective in managing our resources?

Summary: There would be no advantage of exploiting resources with short-term aims. Their exploitation may appear to be advantageous in the short-term but it is highly disadvantageous in the long- term. By doing so, we may be able to enjoy the comforts Of life but we would damage our environment gradually. The exploitation of natural resources with short-term aims are advantageous for present generation to meet their daily requirements whereas management of natural resources with long-term perspective are aimed to fulfill the needs of future generation and to maintain their sustainability.


Question: Describe how communities have conserved and protected forests and wildlife in India

Summary:
In India many traditional communities still live in the forests and depend on their livelihood for forest produce. These communities are working hand in hand with the government to conserve forests.
In Sariska Tiger Reserve, Rajasthan, villagers fought against mining activities. In Alwar district of Rajasthan, local communities belonging to five villages have set their own rules and regulations in 1,200 hectares of forest land. They have named it as the Bhairodev Dakav ‘Sonchuri’. Hunting is not allowed in these lands and outside encroachments are prohibited.
The famous Chipko movement was started in the Himalayan region to stop deforestation. People belonging to the local community took to afforestation in a big way. Indigenous species were cultivated and protected.
Involving local communities in protecting the environment, and stopping degradation of forests has reaped many benefits.


Question: What is biodiversity? Why is biodiversity important for human lives? How have human activities affected the depletion of flora and fauna?

Summary: Biodiversity is the degree of variation of life forms within a given ecosystem, or on an entire planet. There are millions of living organisms on planet earth. All these living organisms, including man, are interdependent on each other. Cutting down of forests for agricultural expansion, large scale developmental projects, grazing and fuel wood collection and for urbanization has led to the depletion of flora and fauna.


Question: What is water scarcity and what are its main causes?

Summary: Water scarcity is the shortage of water but it is not only associated with regions having low rainfall or those that are drought-prone. The availability of water resources varies over space and time, mainly due to the variations in seasonal and annual precipitation, but water scarcity in most cases is caused by overexploitation, excessive use and unequal access to water among different social groups.


Question: What are the various advantages and disadvantages of multi-purpose river projects?

Summary: Regulating and damming of rivers affect their natural flow causing poor sediment flow and excessive sedimentation at the bottom of the reservoir, resulting in rockier streambeds and poorer habitats for the rivers’ aquatic life. Dams also fragment rivers making it difficult for aquatic fauna to migrate, especially for spawning. It has great ecological consequences like salinisation of the soil. At the same time, it has transformed the social landscape i.e. increasing the social gap between the richer landowners and the landless poor. The dams that were constructed to control floods have triggered floods due to sedimentation in the reservoir. Moreover, the big dams have mostly been unsuccessful in controlling floods at the time of excessive rainfall. It was also observed that the multi-purpose projects induced earthquakes, caused waterborne diseases and pests and pollution resulting from excessive use of water.


Question: How is the weather in Gotland? How does it affect the tourism industry in Gotland?

Summary: Gotland features a semi-continental variety of marine climate. This causes larger seasonal differences than the typical marine climates. However, in the isolated places of Gotland, such as Hoburgen or Östergarnsholm, the seasonal differences are much less. This leads to warmer autumns and winters, and colder springs and summers in such places. The sea around Gotland remains ice-free all year round, as winters are typically above freezing temperature. However, during rare extreme cold waves, the sea does witness icebergs. The sunny climate during the summers, mild weather in winters and ice-free waters contribute positively towards the tourism industry.


Question: How was the Maserati Quattroporte physically? How many seats did it offer? What was the structure like? What did it look like?

Summary: The Maserati Quattroporte was a four-door luxury sports sedan. The first generation featured a steel unibody structure. The front suspension was made with coil springs and hydraulic dampers and was independent for both wheels. The brakes were developed using solid Girling discs. It featured a five-seater interior. The design of the car was given by a Turinese coachbuilder Pietro Frua, and it looked like a special 5000 GT designed for Prince Karim Aga Khan.