past paper questions

• Photographs taken of the image obtained by the light microscope could be further enlarged using a projector. Why might the enlarged image be unable to tell us more about the structure of Yersinia pestis?

  no further resolution
• Outbreaks of plague still occur occasionally. Plague is transmitted by several methods including droplet infection, close contact between people and fleas moving between infected rats and people. Suggest two ways to minimise the spread of an outbreak of plague.

  • wear masks
  • immediate quarantine for those infected
• Asepsis is important because

  • reduces microorganisms/ contamination
• State how a clone of potatoes could be produced for this investigation and explain why it is important to carry out this procedure under aseptic conditions.

  • tissue culture/ micropropagation
• Suggest why it is important to use clones in an investigation such as this.

  • no genetic variation
  • control more variable
• The clones were planted in adjacent fields in order to control variables such as temperature, wind speed and rainfall. Suggest two other abiotic variables that this precaution was intended to control.

  • light intensity
  • soil pH
• Suggest a barrier that makes it difficult for potyviruses to enter the sweet potato cell.

  cell wall
• • black sigatoka = fungus
  • potato blight = protista
  • tuberculosis = bacteria
• explain the differences in the person's initial immune response to the influenza virus with their immune response two years later

  A: memory cells produce a stronger response to antigens B and D

  two years later, has less antigens A and C

  
• describe where the primary and secondary immune responses are taking place and explain the differences between the two processes

  • primary response after vaccination when the person is vaccinated
  • secondary response after infection when the person is infected

  
• . Explain why the response to the subsequent infection is much bigger than the response to vaccination

  vaccination involves:

  • clonal selection
  • clonal expansion
  • differentiation
• bond found in antibody

  • disulphide bond
  • to hold light chain and heavy chain together
• What is meant by the term autoimmune disease

  • abnormal immune response
  • against tissues normally in the body
• Suggest why antibodies specific to nuclear proteins are not normally made.

  • nuclear proteins normally hidden in the nucleus
• Some people are immune to malaria. They produce a specific type of antibody. One way in which antibodies defend the body is by acting as agglutinins. Outline the action of agglutinins

  • join/ clump pathogens
  • phagocytes then engulf pathogens
• Explain why vaccinations are an example of active immunity.

  • antibodies are produced by the person being vaccinated
  • memory cells remain in person being vaccinated
• Explain what is meant by an autoimmune disease and suggest why members of the same family can be sufferers of autoimmune diseases

  • immune system attacks own antigens
  • passed down in genes
• DNA sequences in genes code for polypeptide molecules such as pepsin and titin. Explain why a process known as transcription is necessary for polypeptide synthesis.

  • DNA transcribed to mRNA
  • translation at ribosomes
• The malarial pathogen, Plasmodium, is a protoctist. State two features of organisms that belong to the Kingdom Protoctista

  • eukaryotic cells
  • autotrophic or heterotrophic
• Woese carried out a detailed study of RNA molecules in order to draw his conclusions. Suggest two ways in which the scientific community are likely to have validated Woese’s research

  • peer review
  • replication of work - to see if same results obtained
• Explain how scientists are able to estimate the age of extinct organisms

  • fossils
  • fossils deeper in the ground are older than those closer to the surface
• Identify two features visible in both species that suggest that species A and species B evolved from a relatively close common ancestor.

  • lateral spines
  • segments

  
• Describe the components and events involved in a reflex arc

  • action potential
  • relay neurone
  • motor neurone passes to muscle
• What can you conclude from Fig. 2.1 about the mechanism by which a statocyst acts as a transducer?

  • kinetic energy converted to electrical energy
  • membrane of sensory hairs depolarises

  
• Explain how a specific molecule is used to show that two different species have evolved from a recent common ancestor.

  • sequence of amino acids
  • cytochrome c
  • the smaller the number of differences, the more closely related they are