2018 specimen

• what name is given to genetically identical organisms

  clones
• how many chromosomes are in each body cell

  44
• why are reflex reactions important?

  fast reaction to protect from harm
• Suggest a hypothesis for the effect of caffeine concentration on reaction time

  -Higher caffeine concentration causes shorter reaction time
• 2 biotic factors

  -new pathogen

  -competition

  -other predators
• humans have NO cell wall

  Antibiotics that disrupt the bacterial cell membrane often cause more side effects in humans compared with antibiotics that disrupt bacterial cell walls.
• Antibiotics prevent ribosomes from functioning. How this damage the bacterium?

  can no longer synthesise proteins
• What is mutation

  A change in the DNA/gene
• Suggest how a mutation could cause a different colour in carp

  Produces a different protein/enzyme that is responsible for colour.
• give 2 other reasons why gardeners should use less peat-based compost in the future.

  -reduces biodiversity

  -peat is being used faster than it forms
• Give 2 other advantages of the binomial system

  -same name to everyone

  -The genus part gives information on ancestary
• give one reason why we now have more information to classify organisms

  Improvements to electron microscope
• give 2 features of the domain Archaea

  -Primitive bacteria

  -often from extreme environments
• Describe how quadrats should be used to estimate the number of dandelion plants in a field.

  Answer:

  • placed randomly
  • sufficient num of quadrats used
  • count dandelions in each quadrats
  • Use mean number of dandelions, area of quadrat & area of field to estimate population.
• In one area of the field there is a lot of grass growing in the same area as dandelions.

  Suggest why the dandelions may not grow well in this area.

  Answer (based on mark scheme guidance):

  • Dandelions may not grow well because they compete with grass for resources such as:
  • Light (needed for photosynthesis)
  • Water (needed for photosynthesis and support)
  • Space (to grow and expand roots)
  • Mineral ions (e.g., nitrates, for making proteins)
  • This competition reduces the energy from photosynthesis and nutrient availability, limiting growth and biomass production in dandelions.
• Two students investigated the effect of caffeine concentration on reaction time.Suggest how this method could be improved to produce valid results.[6 marks]

  Answer (from the mark scheme):

  To improve the method for valid results:

  • Use decaffeinated coffee as a control group.
  • Control the volume of coffee each person drinks.
  • Use a blind trial so students don’t know if they’ve had caffeine or not.
  • Keep the ruler start position consistent.
  • Wait a standard time (e.g. at least 10 minutes) between drinking coffee and testing.
  • Control external variables like light or noise in the room.
  • Use the same student for all caffeine concentrations.
  • Repeat the test for each concentration to get reliable data.
  • Test a range of caffeine concentrations, starting from the lowest.
  • Use a caffeine solution (not coffee) to eliminate other coffee ingredients affecting results.
  • Use more participants and calculate a mean reaction time for each condition.
• Moose have distinct characteristics such as antlers.Describe how moose may have evolved to have large antlers.[5 marks]

  Answer :

  • There is variation (within species) in antler size.
  • This variation is caused by different genes.
  • It arises as a result of sexual reproduction.
  • The phenotype most suited to the environment is more likely to survive and breed.
  • Therefore, genes for large antlers are more likely to be passed on to the next generation. ✅
• Drug manufacturers are spending less on research into new antibiotics.

  One reason why is because new antibiotics are rarely prescribed.Some people think that governments should pay drug manufacturers to develop new antibiotics.Suggest why.[3 marks]

  Answer :

  • Antibiotics are being developed at a slower rate than the emergence of new resistant strains.
  • Resistant strains mean we can’t treat common infections.
  • Government funding would reduce future cost of antibiotic-resistant infections.
• Explain why mixing peat with air leads to the release of carbon dioxide.[4 marks]

  Answer :

  • Decay of peat by microorganisms introduced when peat is mixed with air
  • These microorganisms respire using substances in peat as a reactant
  • They also use oxygen introduced with the air
  • This process releases carbon dioxide as a product of aerobic respiration
• Evaluate the two systems as methods for controlling blood glucose concentrations for people with Type 1 diabetes.Give a justified conclusion to your evaluation.[4 marks]

  A:Pros of new system:

  • No need to estimate dose of insulin
  • Less chance of giving too much insulin
  • Better control, so reduces risk of future health problems

  Cons of new system:

  • Line might come out
  • Pump will need refilling
  • Risk of infection

  Justified conclusion:The new system is better because it gives better glucose control and reduces long-term health risks, even though it has some minor drawbacks like maintenance.
• Q: How does the body respond if slightly too much insulin is injected into the body?[5 marks]

  A:

  • Blood glucose concentration goes too low
  • Blood glucose concentration is detected by pancreas
  • Pancreas releases glucagon
  • Glucagon causes liver cells to convert glycogen into glucose
  • Glucose is released into the blood