This article was updated on 16 December 2015 after the IAAF announced ammendments some of the entry standards

The race to qualify for athletics events at the Rio 2016 Olympic Games is on. Starting today (May 1) the world’s top athletes can attempt to meet the entry standards set by the International Association of Athletics Federations (IAAF) and take a big step towards earning a place at the first Olympic Games to be staged in South America.

In a change from previous Games, the IAAF has scrapped the system of A and B standards – whereby athletes who failed to achieve the higher standard could still qualify by reaching a lower mark – in favour of a single entry standard.

By equalling or bettering the entry standard (see below for the list), athletes will become eligible to compete at the Rio 2016 Games. However, with each nation having a limit of three athletes per event, achieving the standard does not guarantee participation in the Games, with final decisions being taken by each country’s National Olympic Committee.

“The change in the format for qualification only brings positives,” said Rio 2016’s executive director of sport, Agberto Guimarães, who competed in the 800m at the Moscow 1980, Los Angeles 1984 and Seoul 1988 Games. “Now athletes have to achieve one standard, and this makes it more challenging. It will raise the level of athletics, and not only in the Olympic Games, but also in all the qualifying tournaments.”

The qualification period for the large majority of events runs from 1 May 2015 until 11 July 2016. However, for the 10,000m, marathon, race walk and combined events, it began on 1 January 2015 and also closes on 11 July 2016. There are a total of 2,005 places up for grabs across the sport. If there are places remaining at the end of the qualification period, the IAAF will invite the best ranked athletes to compete, in order to achieve the ideal number of entries in each event. However, there will be no invitations in 5000m, 10,000m, race walks or marathon.

Relay events – the men’s and women’s 4x100m and 4x100m – have a different system: there is a maximum of 16 teams per event and each nation may only enter one team. The top eight in each event at the 2015 IAAF World Relays championship, which takes place this weekend (2 and 3 May), will qualify. The other eight places will be awarded according to the rankings at the end of the qualification period.