Variation and Evolution

• What is Variation?

  Differences in traits or characteristics within a population.
• What are the three causes of variation?

  Genetic variation, environmental variation, and both
• Genetic Variation

  Difference in the genotype of organism of the same species due to the presence of different alleles. It creates differences in phenotype
• What is Environmental Variation

  Differences in phenotype that are acquired during the lifespan of an organism due to the environment factors e.g diet, lifestyle, climate, exposure to light
• There are also 2 types of variation

  Continuous and Discontinuous
• Continuous Variation

  Produces characteristics which do not fall into distinct categories instead of showing a continuous range e.g height and weight
• Discontinuous Variation


  Produces characteristics that fall into distinct categories e.g gender, eye colour, blood group
• Genetic Variation

  Genetic Variation can be due to sexual reproduction or spontaneous mutation
• Reproduction

  This is an important process to pass on genetic material onto the offspring. There are two types asexual reproduction and sexual reproduction
• Asexual reproduction

  Only involves 1 parents due to all genetic material only being from 1 parent there is no variation and all the offspring are genetically identical to both parents and to each other. The offspring are clones. Asexual reproduction only involves mitosis
• Sexual Reproduction

  Involves 2 parents which produce a male sex cell and a female sex cell (called gametes) Fertilisation produces a single cell with a new set of pairs of chromosome. This produces variation in the offspring so we can say they are genetically different from the parents and each other
• Asexual Reproduction: Number of parents

  1
• Asexual Reproduction: Gametes Required 


  No
• Asexual Reproduction: Type of cell division involved

  Mitosis
• Asexual Reproduction: Result of genetic variation

  No
• Asexual Reproduction: Examples of where it is found

  Bacteria
• Sexual Reproduction: Number of parents

  2
• Sexual Reproduction: Gametes required

  Yes
• Sexual Reproduction: Type Of cell division involved


  Meisis
• Sexual Reproduction: Result in genetic variation

  Yes
• Sexual Reproduction: Examples of where it is found

  HUMANS
• Name two types of gametes produced by animal

  Sperm and eggs found in the eggs - overy and sperm- testicles
• What does clone mean?

  An organism that is genetically identical to another
• Give one advantage and disadvantage for asexual reproduction

  Advantages: one parents

  Disadvantages: no variation
• Give one advantage and disadvantage for Sexual reproduction

  Advantage: variation

  Disadvantage: Takes time
• Spontaneous Mutation

  New gene are the result from change in the existing genes. We call this change mutation. Mutation are random, most have no effect, some can be beneficial or harmful. Mutation rate can be increased due to ionising radiation the greater the chance of mutation
• A gene mutation may effect an organism phenotype

  • Neutral mutation does not change the sequence of amino acids.
  • Mutation may cause a minor change in an organism phenotype e.g eye Colour
  • Mutation may completely change the sequence of amino acid and could result in non functional protein and severe changes to phenotype
• Inherited Disease

  Mutation may result in the formation of harmful alleles. If these alleles are present in an organism sex cells they may become inherited by offspring
• Cystic Fibrosis

  There are some mutation that cause condition which may be passed on within the family. And example of this is cystic fibrosis which is passed on by the mechanism of inheritance. Cystic fibrosis causes a production of thick mucus that blocks bronchioles. It arises as a mutation and can be inherited as a recessive allele
• Punnet Square of Cystic Fibrosis

  Diagram:

  
• Possible treatment

  There is a potential cause of action which can treat cystic fibrosis and it is called gene therapy. This is not straight forward as the introduction of genes is not sufficien they must be able to work with the body. There are also difficulties in targeting the appropriate cells and it is not a cure for the underlying conditions. The genes can be introduced into lungs tissue via an inhaler
• There are ethical issue surrounding the use of gene therapy

  • Expensive- money could be better invested elsewhere
  • Religious objective to genetic material
  • Health Implications- new gene may have unintended side effect e.g an Emily response
• What is Evolution?

  In every population there is variation. This variation is a result of mutation. Those best suited to their environment survive. They reproduce pass the advantages allele onto their offspring. Over many generation this becomes the dominant allele. this is evolution.
• Who had the idea of evolution and natural selection

  Charles Darwin and Alfred Wallace
• Natural Selection

  Evolution is a gradual change in inherited traits within a population over time. It occurs due to natural selection
• Process of natural selection

  1. Genetic variation exist due to spontaneous mutation
  2. Competition between organisms
  3. A mutation may give an organism a selective advantage
  4. Organism is better adapted to the environment and survives
  5. Organism reprodcues, passing on its beneficial alleles
  6. Frequency of advantages alleles increase
• Extinction

  When species become extinct all members of the species have died.
• Factors causing extinction

  • Organism are not adapted to their environment
  • Organism have not adapted rapidly enough to change environment conditions
  • Outcompeted by better adapted species
• Modern day evolution

  • Antibiotic resistant bacteria
  • Pesticides resistance
  • Warfarin resistant rats
• Antibiotic Resistance

  Development of antibodies is a good study of evolution as bacteria reproduces rapidly