Bio

• Mendel


  Pea plants

  hereditary units

  recessive and dominant genes
• Darwin and wallace


  Evolution

  natural selection
• Lamarck


  organisms could acquire new traits during their lifetime, and that these traits could be passed to their offspring
• A mutation is a change in the DNA sequence of an organism.
• Mutations can occur spontaneously in our cells, but certain factors can increase the risk.
• Carcinogens increase risk of mutations and are found in cigarettes
• A triplet, or a codon, is a set of three bases which codes for one amino acid.
• Most mutations don't have any significant effect, only very rarely will they impact the organism
• Non-coding DNA often controls the expression of coding DNA, meaning the proteins it codes for will be produced
• Substitution mutation


  One base in the sequence is replaced with a different base 
• Insertion mutation


  An extra base is added into the sequence
• Deletion mutation


  A base is deleted
• Deletion and insertion mutations have a much larger effect than substitution mutations as they disrupt all of the triplets after the mutation
• Transcription


  The copying of a single gene of DNA, to mRNA
• Translation


  The combination of amino acids to form a polypeptide
• A chain of amino acids is called a polypeptide
• More oxygen ➔ more aerobic respiration ➔ more energy available ➔ faster growth and decomposition 
• Higher temperature ➔ particles have more kinetic energy & enzymes are closer to optimum temperature ➔ higher rate of reactions ➔ more decomposition


  However, if temperature rises too high, it will denature enzymes, decreasing the rate of reaction and therefore decreasing the rate of decomposition.
• Decomposers need water to survive, so the rate of decomposition increases in moist conditions. 

  However, if the soil becomes waterlogged then the oxygen levels will fall, which will decrease the rate of decomposition. 
• The mixture of gases this produces is known as 'biogas', and the most important of the gases is methane.

  When methane is combusted (burned), it releases a lot of energy, which can be used for cooking, heating, or generating electricity. 
• Biogas generators are large containers in which animal or plant waste is left to decay anaerobically. Importantly, there cannot be any oxygen in the container. If there is oxygen, the microorganisms will respire aerobically and won't produce as much methane
• Once the biogas is removed from the tank, a sludgy material is left over, which contains a high density of useful minerals. This can be spread on fields like fertiliser
• Diets change as countries become wealthier, and this means food is often transported around the world, and more meat is being consumed (which is less efficient to produce than plant-based foods
• Agricultural inputs can be expensive. Fuels, pesticides, fertilisers, animal feed etc are all expensive and these costs are often passed onto the consumer, which means food becomes more expensive.
• Increased consumption of foods that have to be transported long distances across the world Is also inefficient
• • The effect of temperature on the rate of decay can be observed using milk.
  • As milk takes a long time to decay, lipase and sodium carbonate are added to speed up the decay.
  • As milk decays, its pH reduces. This can be observed with an indicator called Cresol red
• • Use a water bath to heat all of the components to a given temperature.
  • Mix the milk, sodium carbonate and Cresol red. The resulting solution should be purple.
  • Add lipase to the solution and start timing.
  • When the solution turns yellow, stop timing.
  • Repeat using different temperatures.
• • The independent variable is the temperature.
  • The dependent variable is the time taken for the solution to turn yellow.
• Seed germination

  1. Independent variable - Light exposure.
  2. dependent variable - Height of seedlings.
  3. Control variables - Type of seeds, volume of water, germination environment. 
• P stands for phylum
• G stands for genus
• Keep pond clean or froggy gets sick
• The 3 domains are:

  • Archaea - primitive bacteria.
  • Bacteria - true bacteria.
  • Eukaryota - organisms possessing complex sub-cellular structures (protists, fungi, plants and animals)
• Cloning

  1. Find a plant with desirable characteristics that you want to clone.
  2. Take very small pieces of plant tissue (called explants) from the tips of stems.
  3. Sterilise the explants to remove any microorganisms.
  4. Place the explants in a nutrient medium (agar) and let them grow into small masses of cells called calluses. The nutrient medium should also contain growth hormones. 
  5. Transfer the calluses to soil where they can grow into plantlets (basically baby plants).
  6. The plantlets can then be transferred to their own pots to develop into genetically identical adult plants.
• Why cutting is better than micropropagation

  Cuttings is quicker

  Cuttings is cheaper 

  Cuttings requires less technical expertise/equipment

  Don't have to worry about sterilisation so much for cuttings 
• Plant nutrients

  nitrates for amino acids / proteins / DNA / genetic material etc

  phosphates for DNA / genetic material / ATP / cell membranes etc

  glucose for energy/ATP/respiration

  magnesium for chlorophyll/chloroplasts
• Micropropagation

  Cut a small piece of plant tissue, an explant, from the tips of stems, and sterilise them to remove microorganisms. Place the explants in a petri dish that contains agar jelly with growth hormones and nutrients like glucose and mineral ions. Once they grow a bit into calluses, transfer them to soil so they can grow into plantlets. Finally transfer them to their own pot. Ensure that the whole process is done at a reasonable temperature and that the plants get enough light and water.
• 1. Hard body parts, such as bones and shells, which decayvery slowly, are gradually replaced by minerals, forming rock-like substances.
  2. Animals can leave impressions or casts, such as footprints or burrows. These become covered by layers of sediment, which eventually become rock.
  3. Some parts of organisms may not decay at all. For example, dead animals and plants can be preserved in amber, peat bogs, tar pits, or in ice.
• Wallace


  speciation
• Speciation is the process by which a population of organisms becomes reproductively isolated from other populations