Biology HL
Species, Genomes and Identification
- 1.
Two bird populations can interbreed and produce fertile offspring. A bacterium reproduces by cell division and can receive genes from other bacterial lineages. Apply the biological species concept to the birds, then explain two difficulties in applying the same criterion to the bacterium. Suggest an alternative type of evidence that can help classify bacterial lineages.
[4 marks] · no calculator - 2.
Four hypothetical invertebrates have these observable features: A has six legs and wings; B has six legs and no wings; C has eight legs and no antennae; D has more than eight legs and antennae. Construct a dichotomous key identifying all four using only these supplied features.
[4 marks] · no calculator - 3.
A hypothetical pond-water DNA sample contains a barcode matching a reference for frog species F. Explain how this can help identify biodiversity, why it does not prove a live frog was present at the instant of sampling, and give one control against contamination.
[4 marks] · no calculator - 4.
Hypothetical organisms A and B have 98% identity in one short DNA barcode. They have not been tested for interbreeding. Explain why the barcode can support an inference of relatedness but cannot by itself demonstrate that A and B are the same biological species. Identify one useful additional line of evidence.
[3 marks] · no calculator - 5.
Use this hypothetical dichotomous key: 1, wings present -> go to 2; wings absent -> group W. 2, one visible wing pair -> group X; two visible wing pairs -> go to 3. 3, hard protective forewings -> group Y; membranous forewings -> group Z. An intact specimen has two visible pairs of wings with hard forewings. Identify its group and explain one reason a damaged specimen could be misidentified.
[3 marks] · no calculator