Darragh Leader comes into the side at full-back for his first appearance of the tournament, having recovered from a hand injury he packed up earlier in the year.
Rory Scannell reverts to the inside centre position with Steve Crosbie returning at out-half. He has recovered from the hamstring injury he picked up playing against Wales in the opening Six Nations game.
Josh van der Flier has been promoted from the replacements bench to be named at openside flanker with Ryan Murphy moving to number 8.
Jerry Sexton, Eoghan Masterson and Mark Roche have been named among the replacements.
Speaking ahead of Friday's encounter with the Scots, Ruddock said: "We are pleased to have banked a win against England but that's behind us now as we attempt to defeat a much improved Scotland side under Sean Lineen.
"The Scottish side are very well coached and on their own patch they will be a very difficult hurdle to overcome."
IRELAND UNDER-20 Team & Replacements (v Scotland Under-20s, 2013 RBS Under-20 6 Nations Championship, Netherdale, Galashiels, Friday, February 22, kick-off 7.30pm):
15 - Darragh Leader (Galwegians/Connacht)
14 - David Panter (Corinthians/Connacht)
13 - Tom Daly (Lansdowne/Leinster)
12 - Rory Scannell (Dolphin/Munster)
11 - Rory Scholes (Belfast Harlequins/Ulster)
10 - Steve Crosbie (Old Belvedere/Leinster)
9 - Luke McGrath (UCD/Leinster) (capt)
1 - Peter Dooley (Lansdowne/Leinster)
2 - George McGuigan (Newcastle Falcons/Exiles)
3 - Chris Taylor (Malone/Ulster)
4 - Gavin Thornbury (UCD/Leinster)
5 - John Donnan (Ballynahinch/Ulster)
6 - Peadar Timmins (UCD/Leinster)
7 - Josh van der Flier (UCD/Leinster)
8 - Ryan Murphy (Dolphin/Munster)
16 - John Andrew (Ballymena/Ulster)
17 - Ryan Furniss (Worcester Warriors/Exiles)
18 - Adam Boland (Lansdowne/Connacht)
19 - Jerry Sexton (St. Mary's College/Leinster)
20 - Eoghan Masterson (Clontarf/Leinster)
21 - John Creighton (Malone/Ulster)
22 - Mark Roche (Lansdowne/Connacht)
23 - Darren Sweetnam (UCC/Munster)
IRELAND'S RBS UNDER-20 6 NATIONS FIXTURES:
Friday, February 1, 7.10pm - Wales U-20s 17 Ireland U-20s 15, Parc Eirias
Friday, February 8, 7.35pm - Ireland U-20s 16 England U-20s 15, Dubarry Park
Friday, February 22, 7.30pm - Scotland U-20s v Ireland U-20s, Netherdale
Friday, March 8, 7.45pm - Ireland U-20s v France U-20s, Dubarry Park
Friday, March 15, 7pm local time/6pm Irish time - Italy U-20s v Ireland U-20s, Stadio dei Marsi