Genetic variation

• 1. Domain
  2. Kingdom
  3. Phylum
  4. class
  5. order
  6. family
  7. genus
  8. species
• All species names come from the binomial system
• A phylogenetic system arranges species into groups based on evolutionary origins and relationships
• Phylogenetic classification is:

  1. a hierarchy of small groups placed within a larger group
  2. no overlapping
• Each group in a phylogenetic group is called a taxon
• All organisms come from common ancestors
• Courtship behaviour:

  • species specific so members only respond to it
  • used to attract a mate of the right species
  • courtship may be used to classify organisms, how closely related they are
• farming techniques reduce biodiversity
• Must be balance between farming and conservation.
• Agriculture causes:

  • competition between species for light, minerals, food
  • pesticides reduce biodiversity
  • only certain species seen as desirable so little variation in alleles and certain amount of biomass
  • ecosystems controlled by humans
• higher demand for food, changes in farming practices, larger farms and need conversion of natural communities.
• Agriculture negative:

  • removed habitats
  • reduced species diversity
  • removal of woodland
  • monocultures instead of natural meadows
  • Overgrazing
  • draining wetland
• Pesticides and inorganic fertilizers are bad for biodiversity
• Escape of silage stores into water courses and lack of intercropping, are indirect effects of agriculture.
• Management techniques for increasing biodiversity in areas:

  • planting hedges instead of fences as field boundaries
  • planting native trees
  • use of organic fertilizers and intercropping to control weeding
  • use hay rather than grass for silage
  • conservation headland for wild flowers and insects to breed
• Genetic diversity can be measured:

  • frequency of measurable characteristics (some environmental so can be inaccurate)
  • base sequences of DNA
  • base sequences in mRNA
  • the amino acid sequence of proteins encoded by DNA and mRNA
• Genetic bottleneck: big reduction of population, where population dies without reproducing. less variety in alleles, reducing genetic diversity.
• Founder effect: a new colony formed by a few organisms from a population where there is a small number of alleles in the gene pool.
• Adaptations:

  • behavioural (actions)
  • physiological (metabolism?)
  • anatomical (fat, body parts)
• Directional selection: organisms with alleles for characteristics that’s are more likely to survive (usually environmental)
• Stabilizing selection: individuals with alleles for characteristics move towards the middle of the range are more likely to survive and reproduce. (usually not environmental)
• The Types of natural selection:

  1. directional selection
  2. stabilising selection
• Natural selection favours traits which increase reproductive success.
• Meiosis causes genetic variation:

  • crossing over of chromosomes
  • independent segregation of homologous chromosomes
• Number for different combinations of maternal and paternal chromosomes for gamete: 2n
• Number of combinations of chromosomes in offspring as a result of reproduction: (2n)2
• In first division of meiosis: homologous chromosome
• In second division of meiosis:

  chromatids, as homologous chromosomes separated.
• Non-disjunction can occur at either mitosis or meiosis.
• Crossing over occurs when two non-identical chromatids exchange segments during prophase I, resulting in new allele combination on the daughter chromosomes.
• The probability that any one gene will be inherited from either parent is equal.
• A gene mutation is the change of nucleotides base sequence of DNA within a gene.
• Mutations arise spontan during interphase in the cell cycle
• Due to the degenerate nature of the genetic code, not all base substitutions cause a change in the sequence of encoded amino acids.
• Deletion and additions mutations always lead to the change in the amino acid sequence.
• mutagenic agent is a factor that increases the rate of mutations.
• Mutation that causes double the number of chromosomes in a species compared to other of that species is non-disjunction

  (in meiosis)
• Random fertalisation produces new allele combinations.
• Gametes are genetically different due to independent segregation, because of meiosis.
• a gene mutation is a change that occurred in a DNA sequence, forming a new allele.