variation and evolution

• how a fossil forms:

  • animal is covered in sediment first
  • then the soft parts of the animal decay
  • the minerals from the soil enter the bones
• people breed animals for:

  • aesthetics
  • docile pets
  • so they dont have specific genetic defects
• inbreeding increases the chance of

  • passing on disorders
  • being more susceptible to diseases
• species are organisms that reproduce together to form fertile offspring
• if a crop of plants are resistant to a disease,

  • they can kill the weeds among the crops
  • so there is less competition between them for sunlight
  • therefore more crops can grow better
  • therefore more yield
• plasmids are circular rings of dna
• making insulin with genetic engineering:

  • Enzymes are used to isolate the required human gene which is then replicated.
  • This gene is inserted into a vector
  • which is a bacterial plasmid.
  • The modified plasmids also include a gene
  • for antibiotic resistance.
  • The plasmid inserts the genes into the target bacterial cells.
  • An antibiotic is added which kills any bacteria
  • which have not taken up the plasmid.
  • The bacteria that survive will be able to also make insulin.
  • They are grown in a fermenter and the insulin is harvested.