Key Concepts in Biology

• Milli - $10^-3$
• micro - $10^-6$
• nano - $10^-9$
• pico - $10^-12$
• Evolution of Microscopes 


  Light microscopes used light and lenses to form a magnified image of a specimen , possible to see images of cells yet stains are needed to highlight certain parts

  ---> over the centuries , magnification and resolution has increased

  ELECTRON MICROSCOPES

  Uses beams of electrons which has a smaller wavelength than light and

  has much higher magnification and resolving power than it so cells can be studied in finer detail , to better our understanding of sub-cellular structures , the nucleus and cell membrane
• In a Bacteria cell:

  Chromosomal DNA ( circular )- as bacteria cells have no nucleus this floats in the cytoplasm

  Plasmids - Small rings of DNA , code for extra genes to those provided by chromosomal

  Flagella - allows them to move