Genetics and Evolution

• State two kinds of evidence used to show evolution. 

  Fossils

  Antibiotic resistance bacteria
• How are fossils formed?

  Parts of organisms that have not decayed due to conditions needed for decay being absent such as oxygen.

  Parts of organisms that have been replaced by minerals as they decayed e.g. bones

  Traces of organisms are perserved, covered in sediment and becoming rock.  
• Why are there few traces of early life-forms left behind?

  They are mostly soft bodied 
• How do fossils act as evidence for evolution?

  Scientists can identify the ages of the fossils and use them to show organisms change over time.    
• What do branches in evolutionary trees indicate?

  Where new species form 
• What is extinction?

  Where there are no individuals from a species still alive.  
• State the factors that lead to extinction.

  New disease

  Predation

  Competition

  Changes to environment

  Catastrophic events
• What enables bacteria to evolve quickly?

  Their fast rate of reproduction.
• Outline the process of antibiotic resistance in bacteria evolving.

  Mutations in the DNA of bacteria occur causing genetic variation

  Certain strains are resistant to antibiotics and are not killed when the antibiotic is applied

  Resistant strains survive and reproduce.

  Over time, the population of the resistant strains increase.      
• Why are resistant strains of bacteria dangerous?  

  People have no immunity to them and there is no effective treatment
• State the example of the resistant strain of bacteria. 

  MRSA.
• What can be done to reduce the rate of development in antibiotic resistant bacteria?

  Refrain from inappropiately prescribing antibiotics

  Paitents should complete the prescribed course of antibiotics

  Restrict agricultural use of antibiotics 
• Why is it difficult to keep up with emerging resistance strains? 

  Developing antibiotics have a high cost and take a long time to develop.