1. 1
   While swimming in the sea, a woman accidentally brushes her leg against a jellyfish and immediately jerks her leg away from it, before she consciously feels any pain from the sting.

   (a)

   Which type of neurone first carries the impulse from the receptors in the swimmer's skin towards the central nervous system?

   [1 mark]

   • AMotor neurone
   • BSensory neurone
   • CRelay neurone
   • DEffector neurone

   (b)

   Why does the swimmer's leg move away from the jellyfish before she consciously feels the pain?

   [1 mark]

   • ABecause the reflex action bypasses the brain's involvement in coordinating a conscious response, making it very fast
   • BBecause hormones are released instantly into the blood
   • CBecause the leg muscle contracts without receiving any nerve impulse
   • DBecause pain receptors are not involved in this response

   (c)

   Describe the pathway of the reflex arc that causes the swimmer's leg to move away from the jellyfish, in terms of the neurones involved.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hospital microbiology department reports that an increasing number of patients are being infected with a strain of bacteria that no longer responds to the antibiotic that used to successfully treat it.

   (a)

   What is the most likely explanation for why this strain of bacteria no longer responds to the antibiotic?

   [1 mark]

   • AThe bacteria have become a virus
   • BThe patients have become immune to the antibiotic
   • CThe antibiotic has changed its chemical structure over time
   • DThe bacteria have mutated and resistant individuals have survived and reproduced, increasing the resistant population

   (b)

   Why can this antibiotic-resistant bacterial infection not simply be treated with an antiviral drug instead?

   [1 mark]

   • AAntiviral drugs work equally well against bacteria and viruses
   • BBacteria and viruses have identical structures
   • CThe infection is caused by bacteria, not a virus, so an antiviral drug would not be effective against it
   • DAntiviral drugs kill all pathogens regardless of type

   (c)

   Suggest two ways in which hospitals can help to slow down the rate at which antibiotic-resistant bacteria develop and spread.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student who has just eaten a large, sugary breakfast is later tested by a school nurse, who explains how the body monitors and controls the concentration of glucose in the blood as part of maintaining a constant internal environment.

   (a)

   Explain what is meant by homeostasis, referring to receptors, coordination centres and effectors in your answer.

   [3 marks]

   (b)

   Explain how the pancreas responds to the rise in blood glucose concentration after the student's sugary breakfast, and how this brings blood glucose back to a normal level.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A group of hikers is trekking across a hot desert during the day and experiences a large drop in temperature at night, while also having to carefully manage their water intake because they are sweating heavily and producing very little urine.

   (a)

   Explain how the hikers' bodies respond, during the hot day and during the cold night, to keep their core body temperature close to normal, referring to blood vessels, sweat glands and muscles.

   [6 marks]

   (b)

   Explain how the hikers' kidneys and the hormone ADH help to control the water content of their blood, given that they are sweating heavily and producing very little urine.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A dolphin trainer at a marine park teaches a dolphin to touch a target with its nose by rewarding it with a fish each time it performs the action correctly, over many training sessions.

   (a)

   What type of learned behaviour is being used to train the dolphin in this example?

   [1 mark]

   • AInnate behaviour
   • BImprinting
   • COperant conditioning
   • DHabituation

   (b)

   Why does giving the dolphin a fish immediately after it touches the target help it learn the behaviour?

   [1 mark]

   • AIt has no effect on learning
   • BIt punishes the dolphin, making it less likely to repeat the behaviour
   • CIt is an example of an innate reflex
   • DIt reinforces the connection between the action and a positive outcome, making the dolphin more likely to repeat the behaviour

   (c)

   Explain how conditioning of this kind could be useful for humans training captive animals for specific purposes.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A child catches chickenpox for the first time and develops a fever and a rash, but after a week or two the child's immune system clears the virus, and the child is then immune to catching chickenpox again for many years.

   (a)

   Which cells in the child's blood are mainly responsible for producing antibodies against the chickenpox virus?

   [1 mark]

   • AWhite blood cells
   • BRed blood cells
   • CPlatelets
   • DPlasma cells only found in muscle tissue

   (b)

   Why does the child not usually catch chickenpox again after their first infection?

   [1 mark]

   • AThe virus cannot survive in humans a second time
   • BThe child's white blood cells can now respond rapidly, producing the correct antibody quickly if the virus is encountered again
   • CChickenpox is not caused by a pathogen
   • DThe child's red blood cells now destroy the virus on contact

   (c)

   Explain how a vaccine against chickenpox could give a child immunity without the child having to catch the disease first.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A patient with damage to part of their nervous system is found to have a slower reaction time than normal when responding to a sudden loud noise, and their doctor explains how the nervous system and homeostatic control systems both help the body respond appropriately to changes.

   (a)

   Explain, using the terms stimulus, receptor, coordinator, effector and response, how a healthy person would normally react quickly to a sudden loud noise.

   [3 marks]

   (b)

   Explain why homeostasis, the maintenance of a constant internal environment, is important for the normal functioning of the patient's body, giving two examples of internal conditions that are controlled.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A school is deciding whether to encourage pupils to get vaccinated during a local outbreak of a bacterial disease, while a science teacher explains to the class how the body defends itself against pathogens both naturally and with the help of vaccines and antibiotics.

   (a)

   Describe the ways in which white blood cells help to defend the body against pathogens, and explain the difference between how bacteria and viruses cause illness in the body.

   [6 marks]

   (b)

   Evaluate the advantages and disadvantages of vaccinating pupils against this bacterial disease, compared with relying on antibiotics to treat pupils only if they become infected.

   [6 marks]

   Total for question 8: 12 marks

End of questions