Ends 8.15.

Ocean Odyssey
Neri's father had a mission to save the oceans. Can she find the machine to complete the quest? (R) (S)

7.25 Histeria
The ancient Aztec civilisation features in another animated exploration of characters and events in history. (R) (S)

7.45 Short Change
The consumer series tests remote-controlled cars and unmuddles a Harry Potter card game. Presented by Angellica Bell, Rhodri Owen and Ortis.
Shown yesterday at 5pm on BBC1 (S) (W)

Ends 10.50.
WEBSITE: [web address removed]

Pablo the Little Red Fox
Another helping of fun with the mischievous cub, his brother Pumpkin and his sister Poppy. (S)

8.25 The Story Makers
Jackson discovers where snow comes from.
With Danny John-Jules, Nick Mercer and Aliex Yuill. (S) (W)

8.40 Clifford the Big Red Dog
Cleo learns a lesson about playing tricks on people when she tries to spook Clifford and T-Bone. (S)

9.00 Teletubbies
Double bill. Tinky Winky and the others watch a girl paint a turkey, then play indoors when it's wet outside. (R) (S)
BBC CD-ROM: Play with the Teletubbies, for PC and Playstation, price £19.99

9.50 Playdays
Poppy wants to say thank you to Peggy Patch for her assistance. What would be the right present to give? (R) (S)

10.10 Tweenies
Double bill in which Judy meets some of the friends' favourite nursery-rhyme characters, then Jake falls short when trying to roar like a lion. (R) (S) (W)
BBC CD-ROM: Ready to Play, for PC and PlayStation, price £19.99

(Repeats are not indicated)

10.50 Storytime (ages 4-5): A New Home for Tiger
(S)

11.05 Numbertime (ages 4-6): More or Less: Three More

11.20 Words and Pictures (ages 6-7): Phonics Year Two: Or

11.35 Watch (ages 5-7): The Songcatcher: Picnic Time

11.50 Zig Zag (ages 7-9): Art: Pattern and Texture

12.10 Landmarks (ages 9-12): Pakistan and Its People: A Family in Lahore
A day in the life of a suburban family living in the busy, historic city.

Business news, with Adrian Chiles and Adam Shaw.

Further live coverage from
Sheffield's Crucible theatre of the semi-finals, played over the best-of-33-frame format.
At this juncture last year,
Ronnie O'Sullivan 's victory of Joe Swail took him to the final for the first time, having thrice fallen at the semi-final stage. For John Higgins , victory over Matthew Stevens signalled a return after his win in 1998. Steve Davis and John Parrott join Hazel Irvine to introduce the action, while Clive Everton , Ray Edmonds , Dennis Taylor , Willie Thorne and John Virgo occupy the commentary positions. WEBSITE: www.bbc.co.uk/snooker
Including at 3.20 News; Regional News (Digital: BBC London News); Weather

Homerpalooza. The Smashing Pumpkins, Cypress Hill and Peter Frampton add their voices when Homer lands a job as a sideshow attraction at a rock show.

Someday Your Prince Will Be in Effect (part 2).
Quincy Jones is among the guest stars as a beautiful girl causes competition between Carlton and Will.

Coverage of the penultimate session of the first semi-final. Introduced from the Crucible theatre in Sheffield by Steve Davis and John Parrott.

Cheviot Hills. In the last of the series about people trying to preserve a traditional way of life, the archaeological and musical legacies of a lonely landscape are explored by expert Paul Frodsham and Northumbrian piper Katherine Tickell. Elsewhere in the Cheviot Hills, which border
England and Scotland, sheep farmers struggle to survive through a bleak winter. Narrated by Bernard Hill.
Producer Graham Johnston ; Editor Keith Ware 35

Lord and Lady Tavistock bid farewell to the "downstairs" staff who have taken care of them for nearly three decades. Elsewhere in the last of the fly-on-the-wall series looking at life at Woburn Abbey in Bedfordshire, son and heir Lord Howland continues to take over running the estate, and a bitter family row erupts over the future of its safari park.
Director Nigel Farrell ; Producer Paul Sommers

Fragrant flowers are on Alan Titchmarsh 's agenda as he begins work on a new scented area for his Hampshire garden. With the arrival of warmer weather, tender plants can be moved from the greenhouse into the open air. Meanwhile, at a Somerset nursery, Chris Beardshaw marvels at hundreds of varieties of peony in full bloom.
Series producer Colette Foster ; Executive producer Tony Laryea BBC MAGAZINES: Gardeners' World, price £2.60. New issue on sale 10 May Gardens Illustrated, L3.50 BBC BOOK: Grow Your Own Cut Flowers, £18.99 RT SHOP: How to Be a Gardener is available as a hardback book for £13.99 (normally £18.99) or as a double video for £14.99 (usually £16.99). Send a cheque, payable to RT Shop. to [address removed]. or call [number removed] (national rate). Peonies from heaven: page 36

Another eight frames of a semi-final will be played this evening. Steve Davis and John Parrott join Hazel Irvine to introduce the latest action from Sheffield.

Presented by Jeremy Vine.

Natasha Walter and Bonnie Greerjoin presenter Mark Lawson for a review of the week's cultural highlights.
Producer Mark Bell Repeated next Sunday on BBC4

Drama. A radical student escaping a campus riot flies to Death Valley. There he meets a restless secretary looking for excitement. An intense relationship develops at Zabriskie Point, a tourist spot, but their blissful tranquillity is soon shattered. With music by Pink Floyd . Widescreen. Review page 54.
Director Michelangelo Antonioni (1970, 15)

Repeats are not indicated.
National Test Revision Revisewise Challenge at Home KS2 Science - support for parents and children preparing for tests.