Practice Paper 2 (DP IB Biology: HL)

Study the following diagram showing some features of specimen A.

Use the dichotomous key below to identify the class that specimen A belongs to.

Specimen A is classified by using a natural classification system.

Define the term 'natural classification'.

Natural classification can be very useful in conducting research in the field of biodiversity.

List two advantages of natural classification systems.

Describe the early events that led scientists to discover exceptions to Mendel’s predicted phenotypic ratios for dihybrid crosses.

Recombinant offspring are those that have a different allele combination to their parents.

Explain how test crosses can be used to identify recombinant individuals in offspring.

A set of identical twins were raised in similar conditions by the same parents. One of the twins fell off a swing, which left a permanent scar on his chin.

State the impact this would have on the phenotypic variation between the twins.

Shepherd's purse (Capsella bursa) is a flowering plant which belongs to the mustard family. Fruit shape in this plant is determined by two alleles, namely allele T for a triangular fruit shape, which is dominant over allele t for top-shaped fruit. A plant with triangular-shaped fruit was crossed with a plant that has top-shaped fruit. All 30 offspring of this cross had triangular-shaped fruit.

State, with a reason, whether there can be certainty that the original parent plant with triangular shaped fruit had a genotype of TT.

DNA was studied by X-ray diffraction by Rosalin Franklin and Maurice Wilkins in the 1950’s.

Explain how X-ray diffraction allowed Franklin and Wilkins to view the molecular structure of DNA.

Today, visualisation software can be utilised to analyse DNA in very high detail. The association between protein and DNA within the nucleosome can be seen.

Describe what may be visualised when analysing a nucleosome.

Many visualisation techniques have been used to understand and study the structure of DNA. Watson and Crick used visualisation techniques, such as Franklin’s X-ray diffraction, to build a physical model of DNA. Their models were also influenced by the findings of other researchers, such as Erwin Chargaff.

Describe how the research findings of Franklin and Chargaff facilitated Watson and Crick to determine the structure of DNA.       

Bowel cancer can result from adenoma polyps. Adenoma polyps form as a result of mutations occurring in dividing cells of the colon lining.

Suggest the differences in the cell cycle of a cancer cell compared with that of a normal intestinal cell.

Compare and contrast the process of cytokinesis in plants and animals.

The graph below shows data produced from a flow cytometer. This measures the number of cells that are labelled with DNA bound to a fluorescent dye, as this is proportional to DNA content. The stages of the cell cycle are indicated.

Suggest why, during the S phase, that the amount of DNA per cell is between 2n and 4n.

One mark is available for clarity of communication throughout the last two questions.

Describe the process of plant micropropagation.

Outline some of the commercial and environmental benefits of micropropagation.

Explain how microarrays are used in genomics to increase our understanding of plant hormones and their effect on gene expression.

One mark is available for clarity of communication throughout the last two questions.

Outline the role of the zona pellucida in an oocyte.

Compare and contrast the processes of oogenesis and spermatogenesis.

Explain the advantages of internal fertilisation to terrestrial animals.