Breaking down the question
The command word is "discuss", which invites a rounded treatment rather than a bare list. The question sets up the standard contrast between open and closed systems of stratification and asks you to examine how much and what kind of mobility each permits. A good answer both explains the contrast and shows that it is a matter of degree.
Begin by fixing the concept of social mobility and its main forms, then map how mobility operates differently under ascription-based closed systems and achievement-based open systems. The social mobility concept, systematised by Sorokin, is the anchor.
At 10 marks, be economical. A crisp definition, a clear open-versus-closed comparison, and a short critical note that real societies are hybrids will cover the ground fully.
How to approach it
Open with a tight definition of social mobility and note the vertical, horizontal, and inter- and intragenerational distinctions, crediting Sorokin. Then set out the closed system, where status is ascribed and mobility is minimal, using caste as the illustration.
Turn to the open system, where status is achieved and mobility is, in principle, free, using the industrial class system. Then add the critical qualification: no system is purely one or the other, and mechanisms such as Sanskritisation show mobility even within closed systems.
Close with a balanced verdict that treats open and closed as ends of a continuum rather than sealed boxes.
Model answer
Social mobility refers to the movement of individuals or groups from one position in the social hierarchy to another. Pitirim Sorokin, who systematised the concept, distinguished vertical mobility — an upward or downward change in rank, wealth or power — from horizontal mobility, which is movement between positions of similar standing. Mobility may also be intragenerational, occurring within a person's lifetime, or intergenerational, measured between parents and children. How far such movement is possible depends on the type of stratification system.
A closed system fixes status by ascription: position is inherited at birth and movement between strata is minimal or prohibited. The Indian caste system is the classic example, with hereditary membership, ritual ranking, and restrictions on inter-dining and marriage that lock individuals into their natal stratum. Here vertical mobility for the individual is largely foreclosed, and status is a matter of birth rather than effort.
An open system, by contrast, allocates status largely by achievement. Individuals may rise or fall according to talent, education and opportunity, and the barriers between strata are permeable. The industrial class system is its standard illustration, where occupation and qualifications can, in principle, override the accident of birth and both upward and downward mobility are common.
The contrast, however, is one of degree rather than kind. Even the supposedly closed caste system permits collective mobility: Srinivas's concept of Sanskritisation describes how lower castes have raised their group status by adopting the customs and rituals of higher castes, and modern education, reservation and urban anonymity have further loosened caste rigidity. Conversely, the open class system is less open than it appears, for inherited wealth, cultural capital and unequal schooling reproduce advantage across generations, so that mobility at the top and bottom is often limited.
Social mobility, therefore, is present in both systems but differs in form and extent. Closed systems restrict it to slow, collective and largely ritual change, while open systems permit rapid individual movement but still constrain it through the inheritance of advantage. The two are best understood as poles of a continuum, with all real societies — contemporary India especially — combining ascriptive and achievement elements.
Examiner's perspective
For a 10-mark answer, examiners expect the definitional part to be quick and accurate — Sorokin and the vertical, horizontal and intergenerational distinctions — so that time is preserved for the comparison. Scripts that merely label caste as closed and class as open, without noting that mobility is a matter of degree, remain in the average band.
The mark is won by candidates who add the critical qualification with concrete evidence: Sanskritisation as mobility within a closed system, and inherited advantage as closure within an open one. Indian illustrations are especially valued in the optional, and a closing line that treats open and closed as ends of a continuum signals the balanced judgement the command word "discuss" rewards.