Old spec Questions FOR PAPER 2

• What is an ecosystem? [1 mark] - Jan 07 Unit 5

  • Habitat/environment + community (/described)
  • OR all the biotic and abiotic factors in an area/in an environment;
• The percentage of the light energy trapped by the producers is very low. Give two reasons why.

  • Reflected/absorbed by water
  • Reflected from producers
  • Transmitted / passes between chloroplasts/ between plants / too few chloroplasts
  • Wrong wavelength
  • Other limiting factor / named example: carbon dioxide / temperature
  • Used to drive reactions in photosynthesis / LOST in photosynthesis
• The biomass of primary consumers is less than the biomass of producers. Explain why.

  • Loss of energy/ heat / use of energy / less energy to be passed on /
  • In respiration
  • In excretion / urine / carbon dioxide
  • Inedible parts / indigestible parts / to decomposers;
• Give one criticism of the method used. Explain why this would reduce the accuracy of the population estimate. [2 marks]

  • Initial sample too small / marked recapture sample too small
  • Small change in data would give large change in population estimate / leads to overestimate of population
  • One day too short
  • Too many marked snails recaptured ! underestimate of population size // too few marked snails recaptured ! overestimate of population size;

  
• Not all the light energy entering the leaves of the oak tree is used in photosynthesis. Give one reason for this.

  • light is wrong colour/frequency/wavelength
  • light does not strike chlorophyll molecule/chloroplasts
  • there is another limiting factor
• Because the forest soil is often nutrient-poor, nitrogen-containing fertilisers may be applied to ensure good crop yields. Use your knowledge of the nitrogen cycle to explain the potential benefit of applying a fertiliser containing ammonium nitrate rather than one containing potassium nitrate.

  1. ammonium nitrate contains more nitrogen per molecule than potassium nitrate
  2. nitrate ions in fertiliser available/ absorbed immediately
  3. ammonium converted to nitrate
  4. by nitrifying bacteria
  5. fertiliser would provide only the initial release of nitrate/potassium nitrate
• Succinate dehydrogenase catalyses one of the reactions in the Krebs cycle. What is the evidence from the drawing that muscle fibre S is a slow muscle fibre? Explain your answer.

  • Contains more/large amount of succinic dehydrogenase (Looking at the diagram)
  • Slow fibres have lots of mitochondria/ slow fibres respire aerobically;

  
• The girl who took part in this investigation was being successfully treated with insulin. The graph shows that on some occasions, the concentration of glucose in her blood was very high. Suggest why

  • Eaten / diet Containing carbohydrate/sugar
  • Glucose absorbed from intestine/into blood
  • Long time after insulin injection/needs more insulin/has not taken insulin
  • Does not convert glucose to glycogen/glucose not taken up from blood;
• Diabetic people who do not control their blood glucose concentration may become unconscious and go into a coma. A doctor may inject a diabetic person who is in a coma with glucagon. Explain how the glucagon would affect the person’s blood glucose concentration.

  • Glycogen to glucose/glycogenolysis
  • By activating enzymes
  • Gluconeogenesis;
• The wolf numbers are given per unit area. Explain why. [2 marks]

  • Allows comparison
  • Different sized areas covered;

  
• What does the Hardy–Weinberg principle predict? [3 marks]

  • The frequency/proportion of ALLELES of a particular gene
  • Will stay constant from one generation to the next/over generations / no genetic change over time
  • MP3 = Providing no mutation
  • no selection
  • population large
  • population genetically isolated
  • mating at random
  • no migration
• White cats are deaf. Would the Hardy–Weinberg principle hold true for white cats? Explain your answer.

  • White/deaf cats unlikely to survive/selected against
  • Will not pass on allele for deafness/white fur to next generation /will reduce frequency of allele

  
• Describe the part played by the inner membrane of a mitochondrion in producing ATP [3 marks]

  • Electrons transferred down electron transport chain
  • Provide energy to take protons/H+ into space between membranes
  • Protons/H+ pass back, through membrane/into matrix/through ATPase
  • Energy used to combine ADP and phosphate/to produce ATP;
• Conservation of grassland habitats involves management of succession. Use the data in the graph to explain why

  • (Grassland consists of) small/annual plants
  • Will be replaced by/outcompeted by woody plants
  • So these (woody plants) must be removed/have growth checked/grazed;

  
• Explain why the scientist did not use glucose as the respiratory substrate

  • Glucose is used/broken down during GLYCOLYSIS
  • Breakdown of glucose/glycolysis in cytoplasm/not in mitochondria
  • Glucose cannot cross mitochondrial membrane/does not enter mitochondria;

  
• The scientist incubated the seaweeds at 80°C. Suggest why incubating them at a higher temperature would NOT produce valid results.

  • Combustion/ would burn/cause loss of substances (other than water)/named substance
  • cause loss of DRY mass

  
• Microorganisms make the carbon in polymers in a dead worm available to cells in a leaf. Describe how. [5 marks, June 10 Unit 4]

  1. Microorganisms are saprobionts/saprophytes
  2. Secrete enzymes onto dead tissue / extracellular digestion
  3. Absorb products of digestion/smaller molecules/named relevant substance
  4. Respiration (by microorganisms) produces carbon dioxide
  5. Carbon dioxide taken into leaves
  6. Through stomata;