‘And Andrew, and Philip, and Bartholemew, and Matthew, and Thomas, and James the son of Alphaeus, and Thaddaeus, and Simon the Cananaean, and Judas Iscariot who also betrayed him.'
Andrew was the brother of Peter (John 1:40). That they are not put together in the list demonstrates that this was not Mark's method (contrast Matthew). Thus James the son of Alphaeus (is this the James the Little of Mark 14:40?) may have been brother to Levi the son of Alphaeus (Mark 2:14), the latter being identified as Matthew by comparison with Matthew 9:9. Alternately they may both have had different fathers, both being named Alphaeus, a not uncommon name. Bartholomew may be ‘son of Ptolemy' or ‘Talmai' and by his association here with Philip may be Nathanael. But Nathanael may not have been one of the Twelve (although John 21:2 probably suggests that he was. It partly depends on what John meant by ‘disciple'). Luke has Judas, the son of James (‘Judas, not Iscariot' - John 14:22), instead of Thaddaeus, (which Matthew possibly, but by no means certainly for many manuscripts have Thaddaeus, has as Lebbaeus. One may have been a new name and one a nickname).
‘The Cananaean derives from a word meaning ‘zealous' and may be an alternative for Zealot, compare Luke 6:15 - ‘Simon the Zealous one'. Judas the Betrayer is common to all. His name ‘Iscariot' may mean ‘man of Kerioth', but not certainly. The anger felt against Judas comes out in that when mentioning him they all describe him as ‘the Betrayer' or equivalent (Matthew 10:4; Matthew 26:25; Matthew 27:3; Luke 6:16; John 6:71; John 12:4; John 18:2; John 18:5).
It is especially interesting that Mark, who has described the calling of Levi (Mark 2:14) almost certainly gives him another name here, probably Matthew. This suggests that his name list was so firmly set in the tradition that he did not want to alter it.
So the twelve are named and clearly intended to be written into the hearts of the hearers and readers. These are to be seen as the foundation of what is to come.