Variation

• Variation

  • Differences in characteristics or individuals
• What is variation due too?

  • The genes that are inherited
  • The conditions in which individuals have developed
  • Sexual reproduction produces different alleles.
• Examples of genetic variation

  • Blood group
  • Skin colour
  • Natural eye colour
• Environmental causes of variation

  • Characteristics of animals/plant species can be affected by factors such as climate, diet and lifestyle.
• Variation within genes

  • Leads to different genotypes and this can be seen as a different phenotype.
  • All variants arise from mutations
• Mutation

  • A change in a gene or chromosome.
  • Mutations arise spontaneously
  • A mutation rarely creates a new phenotype, but if the phenotype is suited to a particular environment, it can lead to rapid changes in a species.
• Natural selection

  • Is a process where organisms that are better adapted to an environment will survive and have more offspring.
  • This means their genes are passed on to future generations.
  • This process is fundamental to the process of evolution.
• Charles Darwin

  • A famous English naturalist who came up with the theory of evolution.
  • He is associated with the term 'survival of the fittest'.
• Selective breeding

  • Is an artificial selection when humans breed plants and animals for particular genetic characteristics.
• Main steps of selective breeding

  1. Decide which characteristics are important enough to select
  2. Choose parents that show these characteristics from a mixed population and breed.
  3. Choose the best offspring with the desired characteristics to produce the next generation.
  4. Repeat the process continuously over many generations until all offspring show the desired characteristics.
• Desired characteristics in plants

  • Disease resistance in food crops
  • Wheat plants that produce a lot of grain
  • Large or unusual flowers
• Desired characteristics in animals

  • Animals that produce a lot of milk or meat
  • Chickens that lay large eggs
  • Domestic dogs that have a gentle nature
• Benefits of selective breeding

  • New varieties may be economically important, producing better quality or more food.
  • Animals can be selected that cannot cause harm.
• Risks of selective breeding

  • Reduced variation can lead to attack by specific insects or disease.
  • Rare disease genes can be unknowingly selected as part of a positive trait leading to problems.
  • Can create physical problems in specific organisms
• Genetic engineering

  • Also known as genetic modification.
  • Involves modifying the genome of an organism by introducing a new gene from another organism to result in a desired characteristic.
• Genetic engineering steps

  1. Enzymes are used to isolate the required gene, this is inserted into a vector, which is usually a bacterial plasmid.
  2. The vector inserts the gene into required cells.
  3. The genes are transferred to animal, plant during early development. This allows them to develop with desired characteristic.
• Plant crops

  • Have been genetically engineered to be disease resistant or to produce bigger fruits.
• Current uses of genetic engineering

  • Bacteria cells have been genetically modified to produce substances such as human insulin.
• GM crops

  • Those that are resistant to insect attack or are herbicide resistant.
  • This produced increased yields.
• Benefits of genetic engineering

  • Is a faster and more efficient way of getting the same results as selective breeding.
  • Improve crop quality and yields.
  • Introduce herbicide resistance which results in less herbicides being used.
  • Insect and pest resistance. The plant produces toxins, which would discourage insects from eating the crop.
  • Sterile insects could be created such as a mosquito
• Risks of genetic engineering

  • The selected gene may cause harm.
  • Some people believe it isn't ethical to interfere in nature. Also GM crop seeds are often more expensive so people in developing countries cannot afford them.
  • GM crops could be harmful.
  • GM crops can cause allergic reactions.
  • Pollen produced by the plants can be toxic and harm insects.