Incorrect Exam Questions

• What is the difference between species richness and index of diversity?

  Species richness only measures the number of different species and doesn't measure the number of individuals
• Explain how a resting potential is maintained across the axon membrane in a neurone

  • Membrane contains many sodium potassium pumps. They pump 3 sodium ions out of the neurone and 2 potassium ions in. Membrane impermeable to sodium ions so they cannot diffuse back in. Creates a sodium ion electrochemical gradient
  • Potassium ion channels allow potassium ions to diffuse back out of the neurone increasing positive charge outside of the neurone
  • Anion concentrations higher inside neurone. Anions have negative charge. This increases electrochemical gradient of the membrane
• Explain why speed of transmission of impulses is faster along a myelinated neuron than along a non-myelinated neuron

  • Myelin provides electrical insulation for the neuron
  • Saltatory conduction allows action potential to jump from node of ranvier to node of ranvier
  • In an unmyelinated neurone, the action potential must travel the entire length of the axon rather than between nodes which takes longer
• Why would adding a respiratory inhibitor to a neurone change resting potential from -70mV to 0?

  To maintain resting potential, sodium and potassium ions are actively transported. This requires energy from ATP hydrolysis. Inhibition of respiration means that no ATP is produced which means that this active transport cannot occur and so the electrochemical gradient is not maintained
• Why does combining genetic information with a lipid increase its uptake into a cell?

  • As it allows the lipid to diffuse through the phospholipid bilayer of the cell (as the cell surface membrane is a phospholipid bilayer)
• Describe a method used to determine mean percentage cover of an area

  Using a frame quadrat - use random sampling to generate coordinates for where to sample. Ensure a large sample size by carrying this out multiple times on different areas. Work out the total percentage cover of the specific organism and then divide by number of quadrats
• Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels

  Micelles contain bile salts and fatty acids. They make fatty acids more soluble in water. These fatty acids are absorbed by diffusion. Triglycerides are reformed in cells and these vesicles move to the cell membrane (exocytosis)
• Give two adaptations of a leaf for gas exchange

  Leaves are very thin in order to provide a short diffusion pathway for gases

  Leaves have stomata on their underside to allow gas exchange

  The mesophyll layer of leaves is full of spongy air spaces so that no cell is too far from gas molecules