variation and evolution

    Cards (138)

    • 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
    • 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 cutting out genes from one organism and transferring them to cells of a different organism
    • 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
    • Spraying herbicides on GM crops
      Does not harm the GM crop
    • Some people question the safety of GM crops, such as potential harm to insects or wildflowers, and want more research on health effects
    • Gene therapy
      The use of genetic engineering to treat inherited disorders in humans
    • The long-term effects of gene therapy are not known, such as the potential effects on other genes
    • Genetic engineering is done at an early stage of an organism's development, such as the embryo stage, to ensure all cells receive the transferred gene
    • Cloning
      Producing genetically identical organisms
    • Humans have been cloning plants for many years
    • Advantage of cloning plants
      • The clone is genetically identical to the original plant, so we know exactly what the clone's characteristics will be
      • Offspring from sexual reproduction would be different
    • Cloning plants by cuttings
      1. Take a small piece of the plant
      2. Dip the end in rooting powder (contains plant hormones)
      3. Roots develop, producing a genetically identical clone