HKDSE Biology case studies
HKDSE Biology · Put your knowledge to work in context.
HKDSE Biology（香港中學文憑考試生物科）是香港考試及評核局（HKEAA）文憑試中甲類（Category A）高中選修科目之一。文憑試科目分為三個類別：甲類高中科目、乙類應用學習科目及丙類其他語言科目，生物科屬於甲類，與物理、化學、科學組合等並列於選修科目名單。成績採用水平參照成績匯報制度（Standards-referenced Reporting, SRR），以第1級至第5 級匯報，考評局亦製作動畫短片講解1至5 級的評級過程。評核安排包括校本評核（SBA），設有科目資訊、分數調整機制及教師手冊；評核大綱、考試報告及樣本試卷均可於考評局網站查閱。成績公布後，考生可循積分覆核及重閱答卷、上訴覆核等途徑提出申請。生物科並不受乙類科目適用年限安排（如至2027、2028或2029考試年度起適用）所影響。備考時，宜先依據考評局公布的評核大綱掌握考核範圍與評核比重，再研讀考試報告了解歷年考生表現，並以樣本試卷及歷屆試題練習作答；同時留意校本評核要求，向學校教師確認校內呈交流程與期限。本頁為獨立整理資料，並非考評局官方網站，亦不代表任何官方立場；報名、費用、考試時間表及最新安排，請以考評局官方公布為準。. Topics on this exam: Biology (Category A Senior Secondary elective subject; content domains not enumerated in the retrieved source). The HKDSE Biology case studies are 5 cases and about 2,675 words.
1Potato Osmosis and the Isotonic Point
Fifty potato cylinders were cut to 3.0 cm and blotted to 1.00 g. Five were placed in each of five sucrose solutions (0.0, 0.2, 0.4, 0.6, 0.8 mol dm^-3) for 30 minutes. Lengths were measured to the nearest 0.1 cm. Median percentage length changes were +6%, +1%, -4%, -9% and -14%.
563 words, about 3 min2Amylase, pH and a Flawed Iodine Assay
Amylase breaks down starch. A student mixed 2 cm3 of 1% starch with 1 cm3 of pH buffer and 1 cm3 of 0.5% amylase at 25°C, then removed samples every 30 s and tested with iodine. Times to reach a colour that gave no blue-black with iodine were: pH 3, 240 s; pH 5, 90 s; pH 7, 20 s; pH 9, 45 s; pH 11, still blue-black at 300 s. For pH 3 only, the student added amylase before the buffer and started timing 20 s later.
505 words, about 3 min3Carrier Screening After an Affected Sibling
A healthy 22-year-old woman is 12 weeks pregnant. Her 4-year-old brother has an autosomal recessive disorder caused by mutations in a single gene; their parents are unaffected. Her partner has no family history of the disorder. The population carrier frequency is 1 in 25.
521 words, about 3 min4Capture–Recapture in a Pond with Tag Loss and Trap-Shy Fish
A student estimated the number of fish in a pond. On Monday, 200 fish were caught, marked with a small fin clip, and released. On Tuesday, 150 fish were caught; 30 had clips. The student calculated 200 × 150 ÷ 30 = 1000 fish.
575 words, about 3 min5Antibody Titres After Vaccination Versus Natural Infection
In a trial, 50 volunteers received two doses of a vaccine (month 0 and month 6); 50 unvaccinated volunteers who had recovered from natural infection were also followed. Antibody titres were: vaccinated group 1:640 at 4 weeks after dose 2, falling to 1:80 at 12 months; naturally infected group 1:1280 at 4 weeks after infection, falling to 1:320 at 12 months. During follow-up, 1 of 50 vaccinated and 8 of 50 naturally infected participants were hospitalised for severe disease. A journalist writes: 'Natural infection gives higher and longer-lasting antibodies, so vaccination is pointless.' The trial was not randomised; the natural-infection group was recruited from a hospital clinic and was on average 12 years older.
511 words, about 3 min