Planning Cell Investigations

Overview

In this 25th lesson of the unit, students apply their understanding of cell structure, transport, enzymes and cell division to design a scientifically valid investigation. Working in groups of three or four, they develop a research question, hypothesis, variables, controls, rationale and risk assessment that could be used in a later practical investigation.

Learning intentions

Students will:

• integrate knowledge of cell structures and processes into an investigation rationale
• explain why a selected variable is biologically significant
• formulate a testable research question and hypothesis
• identify independent, dependent and controlled variables
• plan a fair, safe and feasible investigation.

Success criteria

• I can write a focused research question that can be tested with evidence.
• I can make a justified hypothesis using biological knowledge.
• I can identify the independent, dependent and controlled variables.
• I can explain how my investigation is safe, valid and relevant to cell biology.

Curriculum links

• Students explain how cell structures enable biological processes needed for life, including transport, enzyme activity and cell division.
• Students explain how cells, tissues and systems contribute to complex multicellular organisms by connecting cell processes to biological function.
• Cell structures and functions, cells and their environments, biochemical processes, and cell division are applied through scientific investigation planning.
• Scientific investigation skills are developed through questioning, planning, risk assessment, identifying variables and evaluating validity.

Lesson structure (60 minutes)

1. 0–5 min · Hook and retrieval. Display the opening question in the investigation hook slides: “How could we produce evidence that a cell process is affected by its environment?” Students independently list one cell process and one measurable factor that could affect it, then share responses with a partner. Clarify that the lesson focuses on planning, not conducting, an experiment.

2. 5–13 min · Model a strong investigation. Use the investigation planning slides to model a question such as “How does temperature affect the rate of catalase activity in potato tissue?” Think aloud while identifying the biological rationale, independent variable, dependent variable, controls, repeated trials and a suitable hypothesis. Emphasise that the rationale must explain the significance of the variable to cells, rather than simply state that it is “interesting”.

3. 13–20 min · Planning mini-lesson. Distribute the cell investigation planning workbook and guide students through its success checklist. Explicitly distinguish independent, dependent and controlled variables; explain operational definitions, valid data, reliability through repeats, and risk controls. Students annotate the model investigation on the worksheet and complete a quick “spot the flaw” question.

4. 20–25 min · Group formation and idea selection. Arrange 35 students into groups of three or four and assign roles: facilitator, biology specialist, method and safety checker, and recorder/presenter where applicable. Groups choose or refine an investigation involving cell structure, membrane transport, enzyme activity or cell division, ensuring the proposed variable can be measured with available school equipment and within ethical and safety requirements.

5. 25–48 min · Group investigation design. Groups complete the planning workbook. The teacher conferences with groups, checking that each research question has one clear independent variable, a measurable dependent variable, appropriate controls, a feasible method, at least three planned repeats and a risk assessment. Students must write a biological rationale linking the selected variable to a cell structure or process, followed by a directional hypothesis using “If… then… because…”.

6. 48–55 min · Peer validity review. Display the peer-review prompts in the peer-review and improvement slides. Groups exchange plans with a neighbouring group and identify one strength, one validity concern and one safety improvement. Students return plans and revise at least one section in a different colour, explaining the change.

7. 55–60 min · Plenary and exit response. Use the plenary slides to revisit the question from the hook. Each group gives a 20-second explanation of its variable and biological significance. Students complete the final worksheet prompt: “The most important change we made to improve validity was…, because…”. Collect one plan and one response from each group for review.

Resources

• the complete investigation planning slide deck
• the cell investigation planning workbook
• Whiteboard and markers
• Student science textbooks or class notes
• Access to a list of available laboratory equipment and materials
• Safety data sheets or school risk-assessment guidance
• Coloured pens for peer review and revisions
• Timer

Assessment

• During modelling, question students about the difference between a biological rationale, a hypothesis and a prediction.
• Conference with groups using the checklist: testable question, justified hypothesis, clear variables, controls, repeats, feasible method and risk controls.
• Collect group plans and individual exit responses. Assess whether students connect the selected variable to a cell structure or process and identify how the design supports validity and safety.

Differentiation

• Provide sentence starters on the worksheet, including “The variable is biologically significant because…”, “If…, then…, because…” and “The dependent variable will be measured by…”.
• Offer a choice of investigation contexts and a variable bank for students who need support; permit students to use diagrams or labelled flow charts before writing the full rationale.
• Pair EAL/D students with supportive peers and pre-teach terms such as variable, control, validity, reliability, membrane, substrate and enzyme.
• Challenge confident groups to justify the number of repeats, distinguish reliability from validity, identify a possible confounding variable and propose how results could be represented graphically.
• Assign roles, provide a visible countdown and allow speech-to-text or scribing support where required.