Edexcel A Biology A-Level Core Practical 18 - Habituation to a stimulus - Instructions, method, risk assessment, graph and conclusion

Oct 20, 2026

Uploaded by Kyle

Edexcel A Biology A-Level Core Practical 18 investigates habituation to a repeated stimulus using snails touched between the eye buds. The innate retraction is timed from initial contact until full re-emergence, and the procedure is repeated ten times. A risk assessment covers biohazard contamination and trip hazards, with disinfecting and safe handling precautions. Results should be graphed as touches versus time, then assessed using Spearman’s Rank Correlation to test statistical significance. Conclusions link decreasing response time to reduced presynaptic calcium channel responsiveness and an evolutionary advantage of conserving resources.

LanguageEnglish

CategoryExam

FormatPDF

Pages3

Reading Time8 min

AccessFree to download

Equipment

Method

Risk Assessment

Graph

Conclusion

FAQs

What is the aim of Core Practical 18?

To investigate habituation to a stimulus by timing how quickly snails re-emerge after being touched between the eye buds repeatedly.

How is the experiment carried out?

Dampen a cotton wool bud in distilled water, touch the snail between the eye buds, time full re-emergence, then repeat for a total of ten touches.

How should the results be analyzed?

Plot number of touches against time to re-emerge and use Spearman’s Rank Correlation Coefficient to determine correlation and whether it is statistically significant.

What safety precautions are required?

Use disinfectant and wash hands after handling to reduce biohazard contamination, and keep bags/stools out of the workspace to prevent tripping; seek appropriate assistance in emergencies.

Oct 20, 2026

Uploaded by Kyle