variation and evolution

• what is variation?


  it is the differences in the characteristics of individuals ina population
• what are the reasons for variation?

  • alleles individuals have inherited
  • environment
  • both environment and alleles
• what is mutation?


  it is a random change in a gene or chromosome
• what is the structure of a question for evolution?

  All species have variation because of mutation. For example (the feature in question). This is advantageous because... . Therefore (feature in question) are more likely to survive and reproduce by passing their genes onto the next generation
• how does natural selection / a speciation event occur?


  • animals of the same species get geographically isolated
  • so natural selection occurs so they are better adapted to survive and reproduce
  • genes are passed onto the next generation until the 2 species can no longer have a fertile offspring
• what is selective breeding?


  it is choosing the parents to breed together in the hope they the offspring will have the phenotype you desire.
• what is the structure for a question on selective breeding?

  First, select (the feature you desire). Then breed them together. Then select and breed the offspring that have the desired phenotype of (feature). Repeat this for many generations of (organism) until all (organisms)have the phenotype you desire
• what is the gene pool?

  it is the variation of genes between species
• why is selective breeding bad?

  it reduces the gene pool and this can cause problems such as genetic defects
• what is genetic engineering?


  it is the deliberate modification of an organisms genes
• what are the 3 reasons for genetic engineering?

  • less effort for farmers
  • crops can be created that give higher yield and better quality
  • genetically modified foods could be made healthier with added nutrients and vitamins
• what is antibiotic resistance?

  it is when a bacteria that used to be killed by a drug isn't affected by it anymore
• how does bacteria become antibiotic-resistant?

  • some bacteria are antibiotic-resistant
  • The non-resistant bacteria will be killed by antibiotics
  • The resistant bacteria multiplies
  • The genes will be passed on to the next generation
• what leads to antibiotic resistance?

  the overuse or misuse of antibiotics

  This is because the more antibiotic there is in our environment the more the bacteria will mutate and evolve
• what are the 3 types of overuse and misuse of antibiotics?

  • doctors prescribing antibiotics for incorrect things
  • not completing the antibiotic course
  • using antibiotics on farm animals
• Three domain classification system

  • Archaea (primitive bacteria found in extreme conditions)
  • Bacteria (true bacteria like those in the human digestive system)
  • Eukaryota (animals, plants, fungi, protists like amoeba)
• Using evolutionary trees to show relationships between organisms

  1. Classify living organisms based on data like DNA

  2. Use fossils to classify extinct organisms (but fossil records are often incomplete)
• Linnaeus divided all living organisms into two kingdoms: animal kingdom and plant kingdom
• Linnaeus' classification categories


  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Mnemonic for Linnaeus' classification categories: "King Phillip came over for good soup"
• Binomial name


  Genus and species name of an organism
• Linnaeus' classification system is based on observable characteristics, but modern biology uses more advanced techniques like microscopes and DNA analysis
• Fossils


  Remains of organisms from millions of years ago which are found in rocks
• How fossils form


  1. Parts of organisms have not decayed

  2. Parts of organism are slowly replaced by minerals during decay

  3. Preserved traces of organisms (e.g. footprints, root spaces)
• Many of the earliest forms of life were soft-bodied organisms which rarely form fossils
• Many fossils have been destroyed by changes to rocks in the Earth's crust
• Because there are very few fossils of the early forms of life, scientists cannot be certain how life on earth began
• Fossils show that a huge number of species have become extinct
• Extinct species


  No remaining individuals of that species still alive
• Reasons species can become extinct

  • Catastrophic event (e.g. asteroid collision)
  • Environmental changes (e.g. weather, new disease, new predator)
  • New more successful species evolves and competes for resources
• The extinction of the dinosaurs was eventually led by an asteroid colliding with the Earth