(a) Tertiary sector relates to activities that help in the development of the primary and secondary sectors. These activities by themselves do not produce a good but they are an aid or a support for the production process.
(b) The causes for tertiary sector becoming important sector in India by replacing the primary sector are as follows :
(i) Concept of welfare state and basic services : In a modern welfare state such as India, the government is supposed to provide basic services such as hospitals, educational institutions, defense, posts and telegraphs for the welfare of the people. These functions come under the tertiary sector.
(ii) Development of agriculture and industry : With the introduction of new agricultural tools, the production increased. At the same time invention of machines led to the development of industrial sector. These developments were responsible for increase in demand for services in tertiary sector such as transport, banking etc. Thus, development in primary and secondary sectors led to the importance of tertiary sector.
(iii) Rise in income: As the income of the people rose, there was more demand for services such as, public schools, shops, private hospitals etc., for better facilities.
(iv) Development of information technology : The development of information and communication technology has increased the importance of tertiary sector because now most of the people want to avail these services such as mobile phone, internet cafe etc. More and more people are entering these services. Thus, the tertiary sector has become most important sector in India.

The history of developed countries indicates about the shifts that have taken place
between the sectors as given below:
(i) In the initial stages, tire primary sector was the most important sector. Most of the people were employed in this sector i.e., agricultural sector.
(ii) With the changes in the method of farming, the production increased tremendously. People started trading and other activities. Increase in production of grain also led to the need for transportation and other facilities. Activities increased but still most of the produced goods were natural products from the primary sector and most people were employed in this is sector.
(iii) After the inventions of machines, factories were established to manufacture goods. The industrial sector employed more and more people and the secondary sector became most Important in total production and employment.
(iv) In the past 100 years, there has been a further shift from secondary to tertiary sector in developed countries. This sector is also called service sector because it provides basic service such as teachers, doctors, lawyers, internet cafe, ATM booths. Tertiary sector has become most important in terms of production. At present, it employs the maximum number of people. So
there has been a shift from primary sector to secondary sector and then to tertiary sector or service sector in the developed countries.

In modern democracies, the different forms of power sharing are as given below:
(i) Power sharing among different organs of government.
(ii) Power sharing among governments at different levels.
(iii) Power sharing among different social groups.
(iv) Power sharing among political parties, pressure groups and movements. These are explained in the following way:
(i.) power sharing among different organs of government: The power is shared by three organs of government i.e., legislature, executive and judiciary. Generally, legislature enacts laws, executive executes the law, makes decisions. Judiciary inter-prets the low and protects the rights of the people. It is called horizontal distribution of power because it allows different organs of government placed at the same level to exercise different powers. Such a separation ensures that none of the organs can exercise unlimited power: Each organ checks the others and a balance of power is maintained. For example, in India, executive i.e., Council of Ministers is responsible to Lok Sabha. The Council of Ministers must enjoy the support of the majority in the Lok Sabha. If they loose confidence of the Lok Sabha, they have to resign. Similarly judges are appointed by the executive, but they check the function of executive or laws made by the legislatures.
(ii) Power sharing among governments at different levels? There are governments at the National, State and Local levels. Powers are divided among these governments. For example, in India, there is a division of powers between Centre and the States. There are three lists i.e., Union list, State list and Concurrent list. The residuary powers which have not been included in the three lists are with the Central Government. Now some powers have been given to local governments under the Panchayati Raj system. Such a system is followed in countries where there is federal form of government as in the USA and Belgium. Such division of powers involving higher and lower levels of government is called vertical division of power. However, in countries where there is unitary form of government as in tire Great Britain, there is no division of powers. All the powers are vested in the central or national government.
(iii) Power sharing among different social groups: Sometimes religious and linguistic groups too share power as is the case in Belgium where there is a “community government” which is elected by people belonging to one language community no matter, where they live. Such government enjoys power regarding cultural, educational and language related issues. In
India, seats are reserved for SCs and STs in assemblies and parliament. Such a system is adopted to give minority communities a fair share in power so that they are not alienated from the government as has happened in Sri Lanka.
(iv) Power sharing among political parties, pressure groups and movements:
When no party gets an absolute majority in legislature, different parties come together and form a coalition government, and share power in a democracy. For example, the present UPA
(United Progressive Alliance) government headed by Dr. Manmohan Singh is a coalition government in which power is share by different political parties that represent different ideologies and social groups. In addition to this, different pressure groups, interest groups and movements also directly or indirectly influence the decision making process of the government.
Thus there is power sharing among political parties, pressure groups and movements.