IB Biology SL case studies
IB Biology SL · Put your knowledge to work in context.
IB Biology SL is the standard-level biology course within the International Baccalaureate Diploma Programme, a two-year pre-university qualification taught in schools worldwide and recognised by universities for admission. It suits students who need a rigorous, experimentally grounded biology foundation without the additional depth and breadth of Higher Level, and it often sits alongside chemistry, mathematics or humanities subjects in a broader diploma. The IB Biology SL case studies are 5 cases and about 3,658 words.
1A Hot-Spring Prokaryote and the Limits of 16S rRNA
A soil sample from a hot spring (74 C, pH 3) yields a unicellular organism, strain HS-7. Under the microscope it is 1.2 micrometres long, has no nucleus or membrane-bound organelles and divides by binary fission.
672 words, about 3 min2Agar Cubes, a Flatworm and a Thick Worm
A student cuts three agar cubes containing Universal Indicator, with sides of 1 cm, 2 cm and 3 cm, and places them in dilute hydrochloric acid. The time for each cube to change colour completely is recorded: 1 cm, 8 min; 2 cm, 32 min; 3 cm, 72 min.
724 words, about 4 min3Summer Stratification and a Fish Kill
A shallow lake used for recreation receives runoff from farmland and treated effluent from a sewage works. Monitoring over one summer gives: nitrate 0.3 mg per litre in May rising to 5.1 mg per litre in August; chlorophyll rising from 4 to 95 micrograms per litre; dissolved oxygen at 1 m depth falling from 9.2 to 1.1 mg per litre; dissolved oxygen at the surface falling only from 9.5 to 8.4 mg per litre; fish numbers falling sharply in late August; and a dense green surface scum appearing.
739 words, about 4 min4Dark Grit, Pale Sand and the D Allele
A population of mice lives on a sand dune where the sand is pale. Dark fur is produced by a dominant allele D and pale fur by the genotype dd.
785 words, about 4 min5Two Families, Two Meiotic Errors
A genetics clinic karyotypes children with Down syndrome and finds 47 chromosomes with three copies of chromosome 21 in each case. To work out the origin of the extra chromosome, a microsatellite locus close to the centromere of chromosome 21 is typed in two families.
738 words, about 4 min