Domain: Natural Science — Microbiology
Target concept: The phage endpoint dilution assay conducted in bacterial broth showed a contrast between clear and turbid samples.

Video generation prompt: On the laboratory bench, a row of transparent test tubes containing identical bacterial broth were arranged from left to right. Tenfold serial dilutions of phage were added sequentially, followed by incubation of the test tube rack and subsequent observation.

Evaluation guide:
(i) Target concept: Visual identification of phage-mediated bacterial lysis via serial dilution endpoint assay.
Minimum mechanism: Bacterial broth supports growth; phage infects and lyses host bacteria; lysis eliminates turbidity; absence of lysis permits turbidity; tenfold dilution creates discrete titer steps; endpoint is first clear tube in descending concentration series.
(ii)Storyline: [Phase 1: Setup] Fixed overhead/front view shows empty rack, then identical broth-filled tubes placed left-to-right. [Phase 2: Intervention] Pipette moves sequentially left-to-right, dispensing distinct volumes (implied by tip contact + meniscus rise) into each tube. [Phase 3: Incubation] Static shot holds full rack unchanged for duration implying incubation (no motion, no time-lapse, no cut). [Phase 4: Observation] Camera maintains same framing; leftmost tubes show homogeneous clarity (no particles, full transparency), rightmost show uniform turbidity (cloudy, opaque, no sediment separation); adjacent tubes display unambiguous turbid-to-clear transition. Visibility constraint: All tubes fully in frame, no occlusion, consistent lighting, no parallax.

Manual:
Experimental Procedure
1. Arrange ten transparent test tubes in a row on bench, each filled with identical bacterial broth.
2. Add tenfold serially diluted phage solution left-to-right: highest concentration to tube 1, next to tube 2, etc.
3. Incubate full rack undisturbed.
4. Observe: leftmost tubes are clear (phage lysed bacteria), rightmost are turbid (bacteria grew unimpeded).
Observation of Experimental Phenomena
Clear tubes (left) and turbid tubes (right) appear side-by-side in same rack; sharp turbid-to-clear boundary marks phage endpoint.
Summary of Experimental Principles
Phage endpoint dilution assay relies on binary lysis outcome: clear = complete bacterial lysis (phage present); turbid = bacterial growth (insufficient/no phage). Serial dilution identifies highest dilution causing lysis — the endpoint.

Prompt Grounding rubric:
level_1: No test-tube rack is visible; or the tubes are not arranged in a left-to-right row; or the tubes do not contain bacterial broth; or there is no visual step showing phage dilutions being added to the tubes; or the video shows no incubation period followed by an observation of the tubes.
level_2: A left-to-right row of transparent, broth-filled test tubes is shown, but at least one required element is unclear or missing: (a) the tubes do not all start with the same-looking broth, (b) nothing in the video (such as a pipette moving from tube to tube) implies that serially diluted phage is being added in sequence, (c) the rack is never held in a static shot long enough to imply an incubation period, (d) there is no shot after the implied incubation that lets the viewer look at the tubes again.
level_3: A row of visually identical, broth-filled transparent test tubes sits on the bench; a pipette (or equivalent dispensing motion) moves across the tubes left-to-right, implying sequential addition of serially diluted phage; the rack is then held in a static shot long enough to imply incubation; a subsequent shot shows the same row of tubes for observation. All core elements from the prompt -- bench, tube row, broth, sequential phage dilution, incubation, and observation -- are present.
level_4: All elements of score 3 are present AND: (a) the row visibly reads as a multi-step dilution series, with several distinct tubes each dispensed to individually in strict left-to-right order (an exact tube count is not required), (b) every tube shows matching broth color and transparency immediately before phage is added, (c) the incubation shot keeps the entire rack in view without cutting away, skipping ahead, or fast-forwarding, (d) the observation shot brings every tube's contents into clear, unobstructed view.
level_5: All elements of score 4 are present AND: (a) no object other than the rack, tubes, broth, and dispensing tool ever enters the frame, (b) the dispensing tool touches each tube exactly once, in unbroken left-to-right order, with no tube skipped or revisited, (c) the tubes' position and the camera's framing stay the same from the opening setup shot through the final observation shot, (d) setup, dilution, incubation, and observation occur in that exact order with no unrelated shot inserted between them.

Scientific and Causal Correctness rubric:
level_1: No contrast between turbid and clear tubes appears anywhere in the row; or every tube looks equally turbid or equally clear after incubation; or a turbid/clear difference appears before incubation is implied to be finished; or the pattern of clear and turbid tubes bears no relationship to left-to-right position (e.g., they are scattered with no order).
level_2: Both clear and turbid tubes appear after incubation, but the assay's biology is violated in at least one way: (a) tubes on the left (highest phage concentration) appear turbid instead of clear, (b) tubes on the right (lowest or no phage) appear clear instead of turbid, (c) a turbid tube sits between two clear tubes, or a clear tube sits between two turbid tubes, so there is no single clean transition point, (d) the clear/turbid difference is only visible during incubation rather than persisting into the observation shot, (e) tube contents look colored, foamy, or otherwise unlike a bacterial broth culture.
level_3: After incubation, the tube(s) at the left end of the row -- the highest phage concentrations -- appear clear (transparent, no cloudiness), consistent with phage lysing the bacteria there, while the tube(s) at the right end -- the lowest or no phage -- appear turbid (cloudy, opaque), consistent with bacteria growing unchecked; there is exactly one left-to-right transition from clear to turbid, with no clear tube on the turbid side or turbid tube on the clear side.
level_4: All elements of score 3 are present AND: (a) clarity is confined to the left-hand tubes with no turbid tube appearing further left of a clear one, (b) turbidity is confined to the right-hand tubes with no clear tube appearing further right of a turbid one, (c) any tubes near the transition show a visibly graded change in cloudiness rather than one tube jumping straight from fully clear to fully turbid, (d) no single tube shows both a clear zone and a turbid zone within it (e.g., a visible split between settled and cloudy liquid).
level_5: All elements of score 4 are present AND: (a) every clear tube looks uniformly transparent, with no haze or floating debris, (b) every turbid tube looks uniformly and evenly cloudy, with no streaks or clumps breaking up the cloudiness, (c) the single clear-to-turbid transition is identifiable as the phage endpoint: the last clear tube marks the highest dilution at which phage still lysed the bacteria, and the first turbid tube marks the first dilution at which bacterial growth went unchecked.

Spatiotemporal Consistency rubric:
level_1: The number or position of tubes in the row changes between shots with no dispensing or camera motion to account for it; or the light in the scene appears to move or change intensity between shots with no visible cause; or a tube's glass shape stretches or warps; or the liquid inside a tube sits at a different height than in the previous shot with no dispensing action shown; or the camera view switches abruptly between an overhead angle and an eye-level angle.
level_2: At least one clear continuity break occurs: (a) the rack's position on the bench shifts between shots with no handling or camera motion shown, (b) a tube's liquid level changes between shots without a matching pipette action, (c) the pipette tip vanishes mid-motion and reappears in a different position, (d) the shadows cast by the tubes swing to a new direction while nothing shows the room light itself moving, (e) items on the bench behind the rack appear, vanish, or change shape between shots.
level_3: The tube row keeps the same position relative to the bench and to itself throughout setup, dilution, incubation, and observation; the pipette's left-to-right motion across the tubes is continuous, without skipping ahead or relocating suddenly; the liquid meniscus in each tube sits at a constant height whenever the rack is held still; and the shadows cast by the tubes and rack keep the same direction and depth from the first shot to the last, consistent with a single unmoving light source over the bench.
level_4: All elements of score 3 are present AND: (a) no motion blur ever obscures whether a given tube is clear or turbid, (b) the camera does not drift or wobble during the static incubation shot, (c) focus on the tube contents stays sharp enough that the clear/turbid state of any tube is never ambiguous, (d) the rack and tubes stay rigidly upright, with no glass bending, sagging, or tilting.
level_5: All elements of score 4 are present AND: (a) the pipette dispenses into the tubes in the same strict left-to-right order throughout, with no tube skipped or revisited, (b) the tube row's framing -- position, spacing, and camera distance -- is identical between the opening setup shot and the final observation shot, (c) the liquid meniscus in every tube keeps the same level shape across the whole observation phase, with no tube showing a tilted or broken surface, (d) the setup, dilution, incubation, and observation phases occur without any of them being skipped, reordered, or interrupted by an unrelated shot.