Variation+Evolution

• Variation


  All the differences in the characteristics of individuals in a population
• Causes of variation


  • Alleles inherited
  • Environmental factors
  • Combination of genes and environment
• Genetic variation


  • Examples: hair color, eye color
• Environmental variation


  • Examples: flower color, language
• Variation from genes and environment


  • Example: height in humans
• Mutation


  Random changes to DNA
• Most mutations have no effect on the phenotype
• Some mutations can influence the phenotype
• A small number of mutations determine the phenotype
• Beneficial mutation


  A mutation that leads to a new phenotype that is advantageous in a changed environment
• Evolution


  The change in the inherited characteristics of a population over time through a process of natural selection
• Natural selection


  1. Genetic variation within a population

  2. Differential survival and reproduction

  3. Passing on of beneficial traits to offspring

  4. Change in population over generations
• The Earth is teeming with living organisms, including large animals, small animals, and plants
• There are nearly 9 million different species of animals and plants on Earth, not including microbes
• Only about 1% of the total species that have ever lived on Earth are still alive today, the rest are extinct
• Life first developed on Earth more than 3 billion years ago, starting with simple single-celled organisms
• All species of living things have evolved from these simple life forms
• Genetic variation within a population

  • Rabbits have different alleles for traits like fur thickness, eyesight, and hearing
• Environment gets colder


  Rabbits with thicker fur are more likely to survive
• Predator moves into the area

  Rabbits with better eyesight or hearing are more likely to survive
• Speciation


  When two populations of the same species become so different that they can no longer interbreed to produce fertile offspring, they are considered separate species
• Speciation in rabbits


  • Normal-sized rabbits
  • Pygmy rabbits
• Selective breeding


  Also called artificial selection
• Selective breeding


  • Humans take wild animals and through selective breeding over many generations produce domesticated animals with desired traits
  • Humans take wild plants and through selective breeding over many generations produce domesticated crops with desired traits
• Humans took wolves


  Through selective breeding over thousands of years produced the dogs that we see today
• Examples of selective breeding

  • Domestic dogs selectively bred to have a gentle nature
  • Food crops such as wheat selectively bred to be resistant to disease
  • Animals such as cows selectively bred to produce more meat or milk
  • Certain plants selectively bred to produce large or unusual flowers
• Selective breeding process


  1. Take a mixed population

  2. Select the largest male and female

  3. Breed these together

  4. Select the largest offspring

  5. Breed the largest offspring together

  6. Repeat over many generations
• Inbreeding can cause some breeds to be prone to disease or inherited defects
• Many dog breeds develop inherited disorders such as joint problems, heart disease or epilepsy due to selective breeding over hundreds of generations
• Genetic engineering


  The process of modifying the genome of an organism by transferring genes from one organism to another
• Genetic engineering


  1. Identify the gene to transfer

  2. Use enzymes to isolate the gene

  3. Transfer the gene into a plasmid or virus (vector)

  4. Transfer the vector into the cells of the target organism
• Genetic engineering in medicine

  • Used to produce human insulin in bacteria for treating type 1 diabetes
• Genetic engineering in agriculture

  • Used to create genetically modified (GM) crops that have higher yields, resistance to disease/insects, or tolerance to herbicides
• Transferring a gene at an early stage of an organism's development


  Ensures all cells receive the transferred gene and the organism develops with the desired characteristic
• Some people question whether GM crops are safe, for example they may be harmful to insects or wildflowers
• The long-term health effects of eating GM crops are not fully known
• Gene therapy is the use of genetic engineering to treat inherited disorders in humans
• The long-term effects of modifying human genes are not known, for example the potential effects on other genes
• Cloning


  Producing genetically identical organisms
• Humans have been cloning plants for many years