Domain: Natural Science — Microbiology
Target concept: Microscopic staining shows that eukaryotic cells have a nucleus, whereas bacteria do not.

Video generation prompt: Under the split-screen view of the optical microscope, yeast cells were placed in the dish with a blue border on the left, and rod-shaped bacteria were placed in the dish with a red border on the right; DNA-binding fluorescent dye was added and the observation was recorded.

Evaluation guide:
(i) Target concept: Visual discrimination of nuclear organization via DNA fluorescence in eukaryotes vs. prokaryotes.
Minimum mechanism: Fluorescent dye must bind DNA stoichiometrically and emit upon excitation; yeast nuclear envelope must retain dye concentration in discrete compartment; bacterial nucleoid must lack membrane confinement, yielding uniform signal.
(ii)Storyline: Frame 0–2: Static split-screen showing empty blue-left/red-right dishes under brightfield. Frame 3–4: Dye solution dispensed into both dishes (visible liquid meniscus/contact). Frame 5–6: Transition to fluorescence mode (background darkens, emission appears). Frame 7–10: Stable fluorescence view: left shows punctate intracellular foci in round yeast; right shows uniform rod-filling signal in bacteria. Perspective: fixed-stage microscope view, no pan/zoom, orthogonal top-down angle, no occluding elements, consistent illumination across both fields.

Manual:
Experimental Procedure
1. Set up split-screen optical microscope view: left field-of-view shows a Petri dish with blue border; right field-of-view shows a Petri dish with red border.
2. Place live yeast cells in the blue-bordered dish; place rod-shaped bacteria in the red-bordered dish.
3. Add DNA-binding fluorescent dye (e.g., DAPI or Hoechst) to both dishes evenly.
4. Illuminate with UV/blue excitation and record fluorescence emission.
Observation of Experimental Phenomena
Yeast cells show discrete, bright fluorescent foci inside cells (nuclei); rod-shaped bacteria show uniform, full-cell fluorescence (no discrete foci).
Summary of Experimental Principles
Microscopic staining with DNA-binding dyes reveals that eukaryotic cells (yeast) possess a membrane-bound nucleus containing concentrated DNA, whereas prokaryotic cells (bacteria) lack a true nucleus and have diffusely distributed DNA.

Prompt Grounding rubric:
level_1: No split-screen microscope view is shown; no blue-bordered dish appears on the left and no red-bordered dish appears on the right; no yeast cells appear in the left dish; no rod-shaped bacteria appear in the right dish; the DNA-binding fluorescent dye is never shown being added to either dish.
level_2: A split-screen view appears, but a setup element is wrong: for example both dish borders are the same color instead of blue-left/red-right, or the yeast cells and rod-shaped bacteria are placed in the wrong dish (swapped left/right), or the dye is visibly added to only one dish while the other never receives it.
level_3: The split screen correctly shows a blue-bordered dish on the left holding round/oval yeast cells and a red-bordered dish on the right holding rod-shaped bacteria; the fluorescent dye is visibly dispensed into both dishes; the scene transitions toward an excitation/fluorescence phase, but fluorescence switches on in only one dish, or in neither, so the two dishes cannot yet be compared side by side while both are glowing.
level_4: All setup elements are correct and both dishes are glowing at the same point in the video: split-screen view; blue-left/red-right borders; yeast cells on the left; rod-shaped bacteria on the right; dye visibly added to both; fluorescence visibly on in both dishes simultaneously, but one minor flaw remains, such as brief motion blur over one dish's cells, a border color that looks slightly washed out yet still readable as blue or red, or debris partly overlapping one group of cells without hiding it.
level_5: All setup elements are present and cleanly rendered: sharp split-screen view; left dish has a clearly blue border and holds several intact round/oval yeast cells; right dish has a clearly red border and holds several intact rod-shaped bacteria; the dye is evenly and visibly added to both dishes; fluorescence comes on strongly and steadily in both dishes at the same point in the clip; no occlusion, blur, or distortion in either dish; both borders keep their color and position for the entire video.

Scientific and Causal Correctness rubric:
level_1: Fluorescence never appears in either dish, or appears in only one dish; or the yeast cells glow uniformly all over (no nuclear foci); or the bacteria show punctate spots (incorrectly implying membrane-bound nucleoids); or the cell shapes are biologically wrong (yeast drawn as rods, bacteria drawn as round cells).
level_2: Fluorescence appears in both dishes but the pattern is reversed: yeast glow uniformly with no visible foci while bacteria show discrete bright spots; or cell shapes are distorted (filamentous/fragmented yeast, coccoid instead of rod-shaped bacteria); or the fluorescent signal sits outside the cells, on the dish surface, rather than inside them.
level_3: Fluorescence appears in both dishes; yeast cells are round/oval and show at least one discrete bright intracellular spot (the nucleus); bacteria are rod-shaped and glow uniformly throughout the cell body, but in one dish the localization is ambiguous, e.g., the yeast spot sits at the cell edge rather than centrally, or the bacterial glow leaks slightly past the cell boundary.
level_4: The core phenomenon is correct: yeast cells are intact and round/oval with a discrete, centrally-placed bright spot (nucleus) inside each cell; bacteria are intact and rod-shaped with continuous, even glow filling the cell and sharp edges; no glow appears outside any cell, but a small flaw remains, such as one yeast cell showing two overlapping spots that are hard to read as a single nucleus, or slightly uneven brightness along some bacterial rods, or minor size variation among yeast cells that doesn't break their round/oval shape.
level_5: The phenomenon is rendered with full scientific fidelity: every yeast cell is round-to-oval and shows exactly one (or occasionally two, consistent with a cell that has just divided) sharply defined, centrally-placed bright spot; every bacterium is a straight or gently curved rod of consistent width glowing evenly and continuously throughout its body with no discrete bright spots; the nuclear-foci-versus-diffuse-signal contrast between the two dishes is unambiguous; no cell shape departs from these microbiological norms.

Spatiotemporal Consistency rubric:
level_1: Dish borders jump to a new position between frames; yeast or bacteria vanish or appear without explanation; fluorescence flicks on and off erratically; the left and right dishes swap places mid-video; the microscope view suddenly zooms or rotates; a dish changes size or shape; lighting jumps abruptly from dark to bright within a single cut.
level_2: The split-screen layout survives but a border visibly wobbles or shimmers; a yeast cell or bacterium jumps an unnaturally large distance between frames; fluorescence switches on and off in bursts rather than staying lit; one dish's glow fades noticeably while the other stays bright; a dish's position drifts sideways or up/down over the course of the video.
level_3: The split-screen layout stays stable; both borders stay fixed in position and color; yeast and bacteria stay continuously visible in their own dish; once fluorescence switches on it stays steadily lit; no cell or dish disappears and reappears; no sudden lighting change occurs, but there is a small, easy-to-miss wobble in a border's position, or a brief blur right as fluorescence turns on that clears within a moment.
level_4: All of the above holds, and in addition: the borders stay perfectly rigid; the yeast and bacteria appear essentially stationary, at most showing the faint natural jiggling expected of cells under a microscope rather than any real drift across the dish; fluorescence brightens smoothly with no strobing; lighting stays even and stable across both dishes; there is no tearing, warping, or shifting of perspective, but one dish shows a faint highlight that flashes briefly brighter than its surroundings before settling back down.
level_5: The video shows no spatiotemporal flaws at all: both borders stay perfectly stable in position, color, and sharpness throughout; the yeast and bacteria stay completely still, consistent with cells fixed under a microscope; fluorescence brightens smoothly and then holds at a constant level with no flicker; lighting stays identical across both dishes and unchanging over time; there is no ghosting, ripple, or dropped frame anywhere in the clip.