Biology

• Some organisms exist of just one cell
• Unicellular organisms


  Simple organisms like amoeba that depend on simple diffusion for life, usually too small to be visible with the naked eye
• Unicellular organisms


  • Bacteria
  • Unicellular algae (about 15 to 20 centimeters in size)
• Multicellular organisms


  Organisms that consist of multiple cells and are more complex
• The vast majority of plants and animals are multicellular
• Being multicellular


  • Allows organisms to be larger
  • Allows for cell differentiation
• Tissues and organs


  Groups of specialized cells that function together to carry out life processes
• Unicellular organisms


  • Can carry out all life processes in just the one cell using internal structures called organelles
  • Have a low level of efficiency due to decreased ability to share out life's processes
• Multicellular organisms


  • Highly efficient with division of labor at the cellular, tissue or organ system level
• Unicellular organisms


  Cannot grow large due to limited surface area to volume ratio
• Multicellular organisms


  Can increase the number of small cells to give it a large size overall
• Unicellular organisms


  • Have a short lifespan due to heavy workload on a single cell
• Multicellular organisms


  • Have long lifespans due to relatively smooth workload on individual cells
• Phagocytosis


  Process where food is engulfed and stored in food vacuums inside a unicellular organism
• Types of unicellular organisms


  • Prokaryotes
  • Protists
  • Some fungi like yeast
• All prokaryotes are unicellular, but eukaryotes can be uni or multicellular
• Injury to a unicellular organism

  Can cause death as one cell is everything to them
• Injury or death of some cells in multicellular organisms


  Is not a problem as those cells can simply be replaced
• Diffusion


  The process by which particles move from an area of high concentration to an area of low concentration. It's a passive process that occurs in both living and non-living systems.
• Osmosis


  A special type of diffusion that involves the movement of a solvent (usually water) across a semi-permeable membrane. It's an important process for unicellular organisms and in the body for the regulation of water balance.
• Semi-permeable membrane


  A type of barrier that only allows certain particles to pass through. In the case of osmosis, the membrane allows the solvent to pass through, but not the solute (like salt or sugar).
• High concentration


  An area where there are more particles present than in another area. Particles will move from an area of high concentration to an area of low concentration in order to equalize the concentration.
• Low concentration


  An area where there are fewer particles present than in another area. Particles will move from an area of high concentration to an area of low concentration in order to equalize the concentration.
• Solute


  A substance that is dissolved in a solvent. In the case of osmosis, the solute is usually a type of salt or sugar.
• Solvent


  A substance that is capable of dissolving another substance. In the case of osmosis, the solvent is usually water.