cell differentiation and cell diversity

• differentiation

  • cells become specialised into different types of cells
• meristems

  • where you find stem cells in plants
• tissue

  • group of cells
• organs

  • group of tissue
• systems

  • group of organs
• some specialised animal cells

  • erythrocytes - carry oxygen from the lungs to respiring animals
  • neutrophils - ingest invading pathogens
• stem cells are unspecialised cells that have the potential to differentiate into different specialised cells
• totipotent

  • stem cells which can divide and differentiate to form a whole new organism eg newly fertilised egg (zygote) and the first 8-16 cells from the first few mitotic division
• pluripotent

  • can become any type of tissue but not a whole organism eg embryo larger than 100 cells
• multipotent


  can form a range of cells but not all different types of cells within a tissue eg stem cells in bone marrow can form different blood cells
• unipotent

  • can only form one type of cell (skin cells)
• 3 uses of stem cells

  • replace organs and cells
  • developing new pancreatic tissues
  • new drugs
• sperm

  • many mitochondria carry out aerobic respiration
  • ATP provides energy for the tail to move and propel towards the ovum
  • enzymes are released from the acrosome, enzymes digest the outer protective layer covering the ovum, allowing the sperm to enter the ovum
• epithelial cells

  • is lining tissue
  • squamous epithelial cells are flattened in shape
  • many of the cells have epithelium have cilia
• palisade cells

  • within leaves are adapted for photosynthesis because they are long and cylindrical
  • large vacuole so that chloroplasts are positioned nearer to the periphery of the cell
  • many chloroplast
• guard cells

  • lower epidermis, do not contain chloroplast
  • more flexible and more rigid
  • gaseous exchange can occur
• root hair cell

  • hair like projection greatly increases surface area for absorption of water and mineral ions
  • have special carrier protein in the plasma membrane in order to actively transport the mineral ions in
• connective tissue

  • these hold structure together and provide support eg bone, cartilage
• muscle tissue

  • made out of cells that are specialised to contract and cause movement
• nervous tissue


  made of cells specialised to conduct electrical impulses
• vascular tissue

  • xylem and phloem
• cartilage

  • hyaline cartilage - forms the embryonic skeleton , covers the end of long bones in adults, joins rib to the sternum and also found in the nose
  • fibrous cartilage - occurs in disc between vertebrae in backbone
  • elastic cartilage - makes up the outer ear