What is the difference between a causal and a sectional pressure group?

The difference between a causal and a sectional group is who joins them and why they join them.A causal group is a group dedicated to one cause; with members having a shared purpose or interest in that cause. Generally, causal groups have open membership, meaning that anyone is allowed to join. An example of a causal group would be the Royal Society Protection of Birds (RSPB) who are one of the largest pressure groups in the UK currently. They are a causal group because they are focused on one cause/aim: the protection of birds. Other causal groups include those such as Amnesty International, Campaign for Real Ale (CAMRA) and smaller ones such as Unlock Democracy.A sectional group is a group dedicated to representing one section of society. This can be a profession, an industry or even a religion. They are set up to protect the interests of a section of the population, and as a result tend not to have open membership. Instead, a person must meet some qualifications to become a member: an example of a sectional group would be the British Medical Association (BMA) who represent doctors and whose membership consists exclusively of those concerned with the medical profession, from medical students to junior doctors to GPs. Another example of a sectional group would be the Confederation of British Industry (CBI).