Fundamental unit of life

• Robert Hooke made a chance observation through self-designed microscope


  1665
• Cells


  Latin word for a little room
• Robert Hooke examining cork (comes from bark of tree) has cells
• Robert Hooke realised living things appear to consist of separate units
• Living things appear to consist of separate units which are called cells
• What living organisms are made up of

  • Cells
• Observing cells


  1. Observe under compound microscope

  2. Use high powers

  3. Observe skin from concave side of onion
• Cells are similar even if they come from different sizes of onion and together they form a large structure (onion bulb)
• Cells are the basic building units of all organisms
• Types of organisms


  • Single-celled organisms (e.g. Amoeba, bacteria, Chlamydomonas)
  • Multicellular organisms
• Multicellular organisms come from a single cell, cells divide to produce new cells and assume different functions
• Different types of cells in a multicellular organism

  • Muscle cell
  • Nerve cell
  • White blood cell
  • Fat cell
  • Bone cell
  • Ovum
• Cells


  • Shape and size related to specific function they perform
  • Fixed shape (e.g. nerve cell)
  • Unfixed shape (e.g. white blood cell)
• Every living cell has the capacity to perform certain basic functions which are the characteristic of all living organisms
• Division of labour exists in multicellular organisms, different parts of the body perform specific functions
• Unicellular organisms have specific components (cell organelles) that perform different functions
• Cell organelles constitute the basic unit-cell, found in the same form no matter the organism or function
• Cell theory states that cells are the fundamental units of structure and function in all living things.
• The cell is the basic structural, functional, and biological unit of all known living organisms.
• All living things are composed of one or more cells.