INHERITENCE + RESPONSE

• Classes of organisms as determined by Carl Linnaeus


  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Features living creatures are traditionally classified by


  • Structure and characteristics
• Binomial system of naming organisms


  Genus name followed by species name
• New classification models were proposed due to developments in microscopy allowing better examination of internal structures and improvement in understanding of biochemical processes
• The three domains


  • Archaea
  • Eukarya
  • Bacteria
• Organisms in the domain Archaea

  Bacteria, usually living in extreme environments
• Kingdoms in the domain Eukarya


  • Plants
  • Animals
  • Fungi
  • Protists
• How evolutionary trees are created


  Examining the DNA of different species and analysing how similar the sequences are
• Variation


  Differences in the characteristics of individuals in a population
• Causes of variation within a species


  • Genetics
  • Environment
  • A mixture of both
• Genetic variation

  Variations in the genotypes of organisms of the same species due to the presence of different alleles, creating differences in phenotypes
• What creates genetic variation in a species


  1. Spontaneous mutations

  2. Sexual reproduction
• Mutation

  A random change to the base sequence in DNA which results in genetic variants, occurring continuously
• Types of gene mutation


  • Insertion
  • Deletion
  • Substitution
• How a gene mutation may affect an organism's phenotype


  • Neutral mutation does not change the sequence of amino acids, so no effect on phenotype
  • Mutation may cause a minor change in an organism's phenotype e.g. change in eye colour
  • Mutation may completely change the sequence of amino acids, resulting in a non-functional protein and severe changes to phenotype
• A new phenotype caused by a mutation being suited to an environmental change


  There will be a rapid change in the species
• Evolution


  A gradual change in the inherited traits within a population over time, occurring due to natural selection which may result in the formation of a new species
• Theory of natural selection


  1. Genetic variation exists due to spontaneous mutations

  2. Selection pressures (e.g. competition, disease) exist

  3. Random mutation gives an organism a selective advantage

  4. Organism is better adapted to the environment and survives

  5. Organism reproduces, passing on its beneficial alleles

  6. Frequency of advantageous alleles increase
• How two populations become different species


  When their phenotypes become different to the extent that they can no longer interbreed to produce fertile offspring
• Selective breeding


  The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes
• Main steps involved in selective breeding


  Identify a desired characteristic

  2. Select parent organisms that show the desired traits and breed them together

  3. Select offspring with the desired traits and breed them together

  4. Process repeated until all offspring have the desired traits
• Characteristics selected for in selective breeding


  • Disease resistance in crops

  Higher milk or meat production in animals

  Gentle nature in domestic dogs

  Large flowers
• Advantage of selective breeding


  Creates organisms with desirable features e.g. higher crop yields, greater milk supply, larger fruit, domesticated animals
• Other uses of selective breeding


  • In medical research

  In sports e.g. horse racing
• Disadvantages of selective breeding


  • Reduction in the gene pool

  Inbreeding results in genetic disorders

  Development of other physical problems e.g. respiratory problems in bulldogs

  Potential to unknowingly select harmful recessive alleles
• Genetic engineering

  The modification of the genome of an organism by the insertion of a desired gene from another organism, enabling the formation of an organism with beneficial characteristics
• Uses for genetically modified plants


  • Disease resistance

  Produce larger fruits
• Use for genetically modified bacteria cells


  • To produce human insulin to treat diabetes mellitus
• Benefits of genetic engineering

  • Increased crop yields for growing population

  Useful in medicine e.g. insulin-producing bacteria, anti-thrombin in goat milk, possibility to overcome some inherited disorders

  GM crops produce scarce resources e.g. GM golden rice produces beta-carotene
• Risks of genetic engineering

  • Long-term effects of consumption of GM crops unknown

  Negative environmental impacts e.g. reduction in biodiversity, impact on food chain, contamination of non-GM crops forming 'superweeds'

  Late-onset health problems in GM animals

  GM seeds are expensive, LEDCs may be unable to afford them or may become dependent on businesses that sell them
• Crops that have had their genes modified

  Genetically modified (GM) crops
• Genetically modified (GM) crops

  Crops that have had their genes modified
• GM crops


  • GM golden rice produces beta-carotene (source of vitamin A in the body)
• Long-term effects of consumption of GM crops unknown
• Negative environmental impacts of GM crops e.g. reduction in biodiversity, impact on food chain, contamination of non-GM crops forming 'superweeds'
• Late-onset health problems in GM animals
• GM seeds are expensive. LEDCs may be unable to afford them or may become dependent on businesses that sell them
• Bacillus thuringiensis (Bt)


  Insect larvae are harmful to crops. Bt is a bacterium which secretes a toxin that kills insect larvae
• How genetic engineering is used to protect crops against insects

  1. The gene for toxin production in Bt can be isolated and inserted into the DNA of crops

  2. Bt crops now secrete the toxin which kills any insect larvae that feed on it
• Sexual reproduction

  Type of reproduction involving the production of gametes by meiosis, where a gamete from each parent fuses to form a zygote, mixing genetic information so the resulting zygote is unique