1. 1
   A doctor takes a throat swab from a patient with a suspected bacterial infection. In the laboratory, the sample is examined under a microscope and a rod-shaped microorganism is identified. It has a cell wall, cytoplasm, a single circular loop of DNA and no nucleus.

   (a)

   Which feature of the microorganism shown in the scenario indicates that it is prokaryotic?

   [1 mark]

   • AIt has a cell wall
   • BIt has cytoplasm
   • CIt has no nucleus and a single circular loop of DNA
   • DIt is rod-shaped

   (b)

   Which of the following is NOT one of the eight characteristics shared by all living organisms?

   [1 mark]

   • ARespiration
   • BPhotosynthesis
   • CExcretion
   • DGrowth and development

   (c)

   State two structural features of the microorganism described that show it is a prokaryotic cell.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Students on a woodland field trip collect four organisms for study: an oak leaf from a tree, a spider, a bracket fungus growing on a dead log, and a sample of pond water containing a single-celled organism called Amoeba.

   (a)

   Which of the four organisms collected on the field trip is an example of a protoctist?

   [1 mark]

   • AThe oak leaf
   • BThe spider
   • CThe bracket fungus
   • DThe Amoeba

   (b)

   Which feature is true of the bracket fungus but not of the oak tree?

   [1 mark]

   • AIt cannot photosynthesise
   • BIt is made of cells
   • CIts cells have a cell wall
   • DIt can reproduce

   (c)

   State two features that the oak leaf (from a plant) and the spider (an animal) have in common as eukaryotic organisms.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In 1892, a scientist studying a disease affecting tobacco plants passed infected sap through a filter fine enough to remove all bacteria. The filtered liquid, containing no visible bacteria, still caused disease when rubbed onto the leaves of healthy plants. This was one of the earliest experiments suggesting the existence of viruses.

   (a)

   Explain why passing the disease-causing sap through a filter that removed all bacteria, yet still causing disease, suggested that the infectious agent was not a normal living organism.

   [3 marks]

   (b)

   Describe four features of the structure of a virus, and state why viruses are not considered to be living organisms.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farmer notices that a fungal pathogen is spreading through a wheat crop, causing the plants to wilt, while a separate outbreak of a bacterial pathogen is affecting the roots of potato plants in a neighbouring field. Later, a viral disease is also found to be affecting the wheat crop.

   (a)

   Compare fungi and bacteria as pathogens, describing the structural features of each that a microbiologist would use to identify them.

   [6 marks]

   (b)

   Explain how a virus infecting the wheat crop would differ from the fungal and bacterial pathogens in terms of its structure and how it causes disease.

   [6 marks]

   Total for question 4: 12 marks

End of questions