Biology ch.5

• Glasshouses and polyethene tunnels

  • Protect crops from harsh weather conditions
  • Increase carbon dioxide levels and rate of photosynthesis
  • Trap heat from the Sun to reach optimum enzyme temperature
  • Protect plants from pests and diseases
• Factors affecting crop yield

  • Carbon dioxide
  • Temperature
  • Fertiliser
  • Pest control
• Increasing carbon dioxide levels

  Burn paraffin lamps
• Increased carbon dioxide levels

  Ensures carbon dioxide is not the limiting factor in the rate of photosynthesis
• Increased temperature in glasshouse

  Allows enzymes in photosynthesis to work at optimum temperature, increasing the rate of photosynthesis
• Fertilisers


  • Contain nutrients that allow plants to grow faster
  • Water-soluble minerals absorbed into plant roots by active transport
  • Nitrates required for amino acids and protein growth
  • Phosphates required for respiration and root growth
  • Potassium needed for growth of flowers and fruit, allowing enzyme reactions
• Pest control


  Using pesticides or biological control to prevent insects eating plants
• Pesticides


  • Fungicides
  • Herbicides
  • Insecticides
• Advantages of pesticides


  • Quick and efficient
  • Can kill entire populations
• Disadvantages of pesticides


  • Organisms can develop resistance
  • Non-specific so kills other organisms
  • Bioaccumulation can make it toxic to others in the food chain
  • Have to continuously apply
• Anaerobic respiration in yeast

  Glucose -> Ethanol + Carbon dioxide

  The carbon dioxide bubbles cause the bread to rise
• Investigating anaerobic respiration in yeast

  1. Dissolve sugar in boiled water

  2. Mix yeast with sugar solution in boiling tube

  3. Add layer of oil to prevent oxygen entry

  4. Connect boiling tube to test tube of lime water

  5. Count bubbles over time
• Lactobacillus


  Useful bacteria in making yoghurt

  Breaks down lactose in milk to form lactic acid, lowering pH and denaturing proteins to give yoghurt texture
• Production of yoghurt


  1. Sterilise equipment

  2. Heat milk to 72°C for 15 seconds to pasteurise

  3. Cool milk and add lactobacillus

  4. Incubate at 40°C to allow bacteria to break down lactose

  5. Add flavourings, colourings or fruit before packaging
• Industrial fermenter


  • Requires aseptic conditions

  Needs nutrients for microorganism respiration

  Needs optimum temperature and pH for enzymes

  Requires agitation to distribute nutrients, oxygen, temperature, pH and microorganisms evenly
• Methods in fish farming

  • Maintaining water quality
  • Controlling intraspecific predation
  • Controlling interspecific predation
  • Controlling disease
  • Removing waste products
  • Controlling quality and frequency of feeding
  • Selective breeding
• Selective breeding


  Humans choose which organisms to breed to produce offspring with desired characteristics

  Can lead to inbreeding and reduced gene pool, making species more susceptible to changes
• Genetic engineering


  Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
• Production of human insulin

  Cut insulin gene from healthy individual using restriction enzymes

  Cut virus or bacterial plasmid using same restriction enzyme

  Join sticky ends of gene and virus/plasmid using ligase enzymes

  Place combined loop in vector like bacterial cell to multiply
• Genetically modified crops


  Engineered to be resistant to insects and herbicides, resulting in increased yields
• Transgenic


  Transfer of genetic material from one species to a different species
• Micropropagation (tissue culture)


  Plant cells placed in growth medium with nutrients and hormones to stimulate growth, producing genetically identical clones
• Cloning animals


  Remove nucleus from unfertilised egg cell

  Place adult body cell nucleus in enucleated egg cell

  Stimulate egg cell with electric shock to divide and form embryo

  Implant embryo into womb of female
• Transgenic animals


  Animals containing genes from a different species, used to produce human proteins
• Advantages of cloning


  • Clones produce identical offspring

  Large number of clones can be produced

  Can produce organs for transplants that won't be rejected
• Disadvantages of cloning


  • Decreases variation in population

  More susceptible to disease as no variation