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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.",{"@graph":69,"@context":126},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":20,"@type":76,"position":81},"https://docshare.wps.com/document/exam/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/edexcel-a-biology-a-level-core-practical-18-habituation-to-a-stimulus-instructions-method-risk-assessment-graph-and-conclusion/621367/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/edexcel-a-biology-a-level-core-practical-18-habituation-to-a-stimulus-instructions-method-risk-assessment-graph-and-conclusion/621367.png","ImageObject",300,407,{"name":92,"@type":93},"Kyle","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-29","2026-10-20",true,{"@type":102,"interactionType":103,"userInteractionCount":8},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118,122],{"name":109,"@type":110,"acceptedAnswer":111},"What is the aim of Core Practical 18?","Question",{"text":112,"@type":113},"To investigate habituation to a stimulus by timing how quickly snails re-emerge after being touched between the eye buds repeatedly.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How is the experiment carried out?",{"text":117,"@type":113},"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.",{"name":119,"@type":110,"acceptedAnswer":120},"How should the results be analyzed?",{"text":121,"@type":113},"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.",{"name":123,"@type":110,"acceptedAnswer":124},"What safety precautions are required?",{"text":125,"@type":113},"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.","https://schema.org",{"og:url":83,"og:type":128,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":130,"canonical":83},"index,follow",{"doc_id":132,"site_id":62},621367,1792465427,{"code":4,"msg":5,"data":135},{"doc_id":132,"user_id":136,"nickname":92,"user_avatar":137,"doc_module":4,"category_id":19,"category_name":20,"doc_title":65,"doc_description":67,"doc_content":138,"file_id":139,"file_url":140,"file_type":141,"file_size":142,"view_count":8,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":81,"language":143,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":144,"faqs":145,"seo_title":146,"seo_description":67,"update_tm":133,"read_time":39,"preview_page_count":4},3985741905716,"https://ap-avatar.wpscdn.com/davatar_994ba38a5ba835b3df7d355c54d3ed8d","Edexcel A Biology A-Level Core Practical 18  \nInvestigate habituation to a stimulus.  \nWhen snails are touched between the eye buds they retract into their shells very quickly and take some time to re-emerge. This is an innate response to what is perceived as a threat. Habituation is the decreasing of an innate response, such as this one over time, as the stimulus is repeated and is learned to be benign.  \nEquipment  \n● Snail  \n● Cotton wool bud  \n● Distilled water  \n● Chopping board  \n● Stopwatch  \nMethod  \n1. Dampen the cotton wool bud in distilled water.  \n2. Touch the snail between the eye buds with the cotton wool bud  \n3. Time the length of time it takes for the snail to emerge fully from its shell again.  \n4. Repeat for a total of ten touches.  \nRisk Assessment  \n\n| Hazard | Risk | Safety Precaution | In emergency | Risk\u003Cbr>Level |\n| --- | --- | --- | --- | --- |\n| Biohazard | Contaminati\u003Cbr>on | Use disinfectant; wash hands with soap after handling | Seek assistance | Low |\n| Bags/stools | Tripping | Keep under desks and away from workspace | Seek appropriate medical assistance; clean spillages | Low |\n\nGraph  \n● Plot a graph of number of touches against time to re-emerge from shell.  \nConclusion  \n● Results can be tested using Spearman’s Rank Correlation Coefficient to determine the correlation between the two variables and whether it is statistically significant.  \n● As number of touches increases, the time taken for the snail to re-emerge decreases because the snail becomes habituated to the stimuli. This is because calcium channels in the presynaptic membrane become less responsive to stimuli (the threshold increases) over time, so less neurotransmitter is released into the synaptic cleft.  \n● This is because it is evolutionarily advantageous not to use resources on responding to a benign stimulus.  \nNote: it is important to treat the snails ethically during the experiment and to re-release them afterwards.","cbCaishmzVHGwpSY","https://ap.wps.com/l/cbCaishmzVHGwpSY","pdf",127520,"English","# Equipment\n# Method\n# Risk Assessment\n# Graph\n# Conclusion","[{\"question\":\"What is the aim of Core Practical 18?\",\"answer\":\"To investigate habituation to a stimulus by timing how quickly snails re-emerge after being touched between the eye buds repeatedly.\"},{\"question\":\"How is the experiment carried out?\",\"answer\":\"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.\"},{\"question\":\"How should the results be analyzed?\",\"answer\":\"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.\"},{\"question\":\"What safety precautions are required?\",\"answer\":\"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.\"}]","Edexcel A Biology A-Level Core Practical 18 - Habituation to a stimulus - Instructions, method, risk assessment, graph and conclusion | PDF"]