questions

• 1.Explain how modern phylogenetic techniques have allowed classifications of organisms (eg. sloths) to be updated from earlier anatomical evidence (BOX 1) [2]

  -> physical features

  -> proteinomies

  -> evidence for evolutionary relationships

  • scientists would compare amino acid sequences from the same protein produced by different sloths using DNA profiling
  • more similarities = more closely related
• 2.Suggest how natural selection could have led to the sloth hair being suitable for colonisation by algae (Box 2).

  • A mutation made the sloth hair more suitable for algae to colonise.
  • More algal growth helps newborn sloths survive by… providing extra nutrients (eg. nitrogen and phosphorus)
  • Sloths with the advantageous hair allele more likely to survive, reproduce and pass alleles on to their offspring
  • Over many generations allele frequency increases in the population
• 3.calculate energy transfer efficiency if a 3-toed sloth ingests 2000kJ/day/kg of leaf material (paragraph 5)

  • metabolic rate = energy out = 162kJ/day/kg
  • ETE = energy out/energy in
  • ETE = 162/2000 x100 = 8.1%
• 4.what does a low metabolic rate mean for the sloths?

  • low rate of reaction/enzymes
  • low rate of respiration-> less energy/ATP
• 5.Explain why the low metabolic rate of the sloth could reduce the amount of virus found in their bloodstream (Box 3) [3]

  • Viruses use cell processes to replicate themselves
  • low metabolic rate reduces 
  • rate of reactions and 
  • rate of respiration 
  • so there is less energy/ATP for cellular processes
  • Takes a long time for viruses to replicate and bust out of cells into the blood.
• 6.Explain why arboreal folivores normally have to eat large amounts of plant material a day (Paragraph 6) [3]

  • very little energy is transferred from plants to herbivores because..
  • leaves contain cellulose which is difficult to digest
  • because digestion of cellulose requires particular enzymes (e.g. cellulase)
  • so a lot passes through the digestive system undigested
  • biomass is lost through respiration
  • energy released is used for movement or is lost as heat.
• 7.Explain the differences between the muscles of an olympic weightlifter vs a marathon runner.

  • endurance runners have more slow twitch fibres whereas weightlifter has more fast twitch fibres.
  • Endurance runner’s muscles would be more red because slow twitch muscles have
  • more capillaries (for oxygen supply)
  • more myoglobin (for oxygen storage)
  • more mitochondria (so aerobic respiration can take place)
  • Weightlifter’s muscles rely on anaerobic respiration, providing quick energy when oxygen supply is limited.