bio paper 2

• Classification


  Humans classify organisms based on their characteristics and structure
• Classification system


  1. Divides organisms into smaller and smaller sub-sections

  2. Each sub-section is more specific than the last

  3. Ends with a binomial name
• Binomial name


  • Scientific name made up of genus and species
  • Always written in italics
  • Genus capitalised, species not
• Binomial name for humans

  • Homo sapiens
• Mnemonic can be used to remember classification hierarchy
• Mnemonic for classification hierarchy

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Three-domain system


  Proposed by Carl Woese in 1990 after advancements in chemical analysis
• Three domains


  • Archaea
  • Bacteria
  • Eukaryota
• Archaea and Bacteria


  • Look very similar but have lots of biochemical differences
• Evolutionary trees


  • Represent evolutionary relationships between different species
  • Created by comparing physical features, DNA analysis, and fossils
• Genetic engineering


  A process that allows alleles for desired traits to be transferred into the genome of another organism, to give them the desired trait
• Genetic engineering process


  1. Using enzymes and vectors to change an organism's DNA so it has a desired trait

  2. Cutting out the desired gene from another organism

  3. Inserting it into a vector

  4. Inserting the vector into the organism
• Genetically modified (GM) organisms


  Organisms that contain the new gene from genetic engineering
• GM plant crops


  • Produce bigger fruits
  • Have improved nutritional value or contain additional vitamins
  • Are resistant to certain diseases
  • Produce poisons that kill insects making them resistant to insect attacks
  • Are resistant to herbicides (so herbicides kill weeds and not the crop)
• Bacterial cells


  • Can be modified to produce human insulin which can be extracted and used to treat people with diabetes
• Gene therapy


  Replacing faulty genes with functional copies from another organism
• How genetic engineering works

  1. Genes that code for the desired traits are first extracted from the DNA using enzymes

  2. This gene is inserted into a vector, which is usually a bacterial plasmid or virus

  3. The vector is used to insert the useful gene into the required cells

  4. If the cells are in the early stages of development, they will develop the desired trait as they grow
• Advantages of genetic engineering

  • Potential to be useful in medicine and farming
• Problems with GM crops

  • GM seeds can be very expensive meaning smaller farms will not be able to afford them
  • Herbicide resistant GM crops encourage the use of herbicides which can damage the environment and can be expensive
  • Risk that the genes could be transferred to wild plants by pollinators
  • Modifying the plants to be resistant to herbicides will reduce the biodiversity of the area and have repercussions for animals further up the food chain
  • The effects of GM crops on the humans eating them has not fully been explored and some people believe there could be harmful long-term effects
• Darwin's theory of evolution was once very controversial but is now supported by a variety of evidence
• Fossil records show how organisms have changed over time
• The evolution of antibiotic resistance in bacteria supports our understanding of how advantageous traits are inherited by offspring
• Fossils


  The remains of ancient organisms that are found in rocks
• Fossils


  • They show what organisms looked like millions of years ago
  • They can be used to work out how much organisms have changed and evolved
• Fossil formation


  1. Parts of organisms that will not decay easily get replaced by minerals

  2. Soft material like clay can harden around whole organisms, traces of organisms, burrows or rootlet traces

  3. Certain conditions like ice, peatbogs, amber and tar pits can preserve organisms
• Fossils found deeper in the soil are generally from more simple organisms
• The fossil record is incomplete because many early forms of life were soft-bodied so left very few traces behind and many of the fossils that were made have been destroyed by geological activity
• Evolutionary trees


  • A good way of representing the relationship between different species over evolutionary time
  • They show when speciation has occurred (when lines branch off)
• Forming evolutionary trees


  1. Using data collected from fossil records

  2. Using data collected from DNA sequences
• Evolutionary tree


  • Pigeons are most similar to parakeets because they share a more recent common ancestor
  • Pigeons are least similar to ducks because they share a more distant common ancestor
• Bacteria reproduce by binary fission


  This means they evolve rapidly
• Mutations often occur in the DNA of bacterial pathogens and some of these mutations lead to changes in characteristics of the bacteria and may even cause the bacteria to become resistant to certain antibiotics</b>
• Due to their high rate of reproduction, entire antibiotic-resistant strains can evolve very quickly
• Antibiotic resistance


  It is very beneficial to the bacterial pathogen as it will not be killed by antibiotics, can reproduce a lot more and the population can grow
• For humans or other hosts, antibiotic resistance causes big problems because the antibiotics that are used to treat people with bacterial infections will no longer work
• Scientists try to develop new antibiotics that bacterial strains are not resistant to but the process is expensive and slow
• Some 'superbugs' are resistant to all known antibiotics, such as MRSA which usually affects vulnerable people in hospitals and can be fatal
• Preventing the evolution of antibiotic resistance

  1. Avoid inappropriate prescribing of antibiotics

  2. Patients must complete the full course of antibiotics

  3. Using less antibiotics in farming
• Evolution


  A process by which inherited characteristics in a population change over time due to natural selection
• Natural selection


  The theory that organisms that are more suited to their environment are more likely to survive, reproduce and pass on their advantageous genes