B1

• unicellular - made up of just one cell e.g. bacterium
• multicellular - made up of collection of cells e.g. species of algae
• specialised cells

  • multicellular organisms, there are cells called stem cells that undergo cell division (mitosis), to make identical daughter cells
  • Some of the daughter cells then undergo a process called DIFFERENTIATION to become a specialised cell type, that are adapted to have a specific function
• example of stem cells

  stem cells in the bone marrow can differentiate into the different types of blood cells (red blood cell, white blood cell, platelet
• order of cells

  • organelles
  • cells
  • tissues
  • organs
  • organ systems
• Tissue

  A group of similar specialised cells that perform a specific function e.g. nervous tissue
• Organ

  A group of different tissues that carry out a vital function(s) e.g. heart
• Organ system

  A group of organs with related vital functions that work together to perform body functions e.g. respiratory system