# Follow the evidence

Choose a route that helps you explain your thinking. You can change routes. Use words, a labelled sketch, a table, spoken explanation, AAC or directed card placement. A clear biological reason matters more than a polished drawing. All files and numbers are supplied teaching models.

## Slot 11 · Place the boundary

Read Cards A and B. Name three features shared by Leaf L and Bacterium B and one difference in DNA organisation. Describe where a plant cell wall sits relative to its membrane. On a two-line membrane sketch, place heads and tails and explain one placement. Finish: “This model shows …; it does not tell me …”.

## Slot 12 · Give a component a job

Use Card B. Explain how a channel, a glycoprotein and cholesterol contribute to this animal membrane model. Add a carrier's possible role. Correct this caption: “Every protein is a pump, and cholesterol always increases fluidity.” Keep a specific limit beside your correction.

## Slot 13 · Draw a justified net arrow

Use Card C's Transport File T. For Q, R and oxygen, name the route, net direction and relevant energy statement. Explain why an arrow describes net movement. A separate ion is 10 mmol/L outside and 2 mmol/L inside; a suitable channel is open but no electrical conditions are given. Can concentration alone settle its net direction? Explain the information you still need.

## Slot 14 · Which material crosses?

Use File O in Card D. State what can cross, the temperature and pressure conditions, and the initial net water direction. Give a reason without saying that solute moves by osmosis. Use Card E to distinguish V and X, explaining one feature of each sequence. Name one thing these descriptions cannot tell you about a real cell.

## Slot 15 · New boundary file

Use [Check E's first page](checks/first/E.md) when it is given to you. Keep your first response. Read [the later page](checks/later/E.md) only after that first work is collected. Show how the new information affects your conclusion.

## Slot 16 · Keep the units

Use Card F's rules. A new cube S has edge 30 µm. Calculate its surface area, volume, SA/V and face-to-centre distance. Compare it with P's 10 µm edge: does S have more total surface? More surface per unit volume? Explain both answers.

## Slot 17 · Same volume, different shape

A cube is 2 × 2 × 2 units. A rectangular model is 1 × 2 × 4 units. For a rectangular box, area = 2(lw + lh + wh), volume = lwh. Calculate each area, volume and area/volume. Find each shortest centre-to-face distance. Explain how the thinner model might help exchange and name one reason geometry alone cannot predict an actual cell's exchange rate.

## Slot 18 · How much has been reached?

Use Card G's geometric rule. A model cube has edge 6 mm and a layer 1 mm deep from every face at 5 minutes. For this supplied interval, the layer starts at depth d_start = 0 mm when t_start = 0 min. Average front speed = Δdepth/Δtime = (d_end − d_start)/(t_end − t_start). This is the model's interval average, not a constant future speed, intrinsic diffusion coefficient or molecular flux. Find the central edge and fraction penetrated. Separately calculate the interval-average change in depth divided by elapsed time in mm/min. Explain why those two results answer different questions. Do not extend this one-time value into a constant speed for every later time.

## Slot 19 · Improve a plan

Read Card H. Name the proposed independent variable, the dependent measure, and three conditions to keep constant. Calculate both supplied means and ranges. Give a conclusion about those numbers, one limitation, and a practical improvement to the proposed measurement or repeats. State whether a learner investigation has actually occurred.

## Slot 20 · New cube comparison

Use [Check F's first page](checks/first/F.md) when it is given to you. Preserve your first calculation and claim. Read [F's later page](checks/later/F.md) after collection. Explain which mathematical facts remain supported and which comparison needs greater caution.