MT

organisation in living things : principles and applications of science

  • specialised cells
  • tissues - group of cells with same general structure and function
  • organs - group of different tissues gathered together to perform a function eg : lung
  • organ system - group of different organs gathered together to perform different functions eg : digestive system
  • and these make a whole organism

cell differentiation

  • when a new organism is formed as a result of sexual or asexual reproduction all the early cells are the same.
  • as an organism develops specialisation of cells starts to take place
  • each type of cell will have a specific structure or function
  • this process is called cell differentiation and leads to the formation of tissues
  • once the change has taken place the cells cannot develop into other types of cells

specialised cells

  • plant stem cells :

    • mature plants have differentiated tissue cells but also have stem cells that can develop into the differentiated tissue

    • these stem cells can be found in areas called meristems

    • these exist close to the growing points of plants

    • tip of stems and roots

  • specialised plant tissues include :

    • root hair cells
    • xylem
    • phloem
    • guard cells
    • palisade cells

  • root hair cells

    • root hair cells have long roots which allow them to have large surface area

    • cell wall of a root hair cell is thick which increases rate of absorption

    • water moves in by mitosis

    • concentration of ions is much lower outside the cell than inside

    • ions moved by active transport

    • lots of carrier proteins

    • many mitochondria to provide energy for transport

  • palisade cells

    • palisade cells have many chloroplasts to transport light energy for photosynthesis situated in the upper surface of leaf close to light
    • columnar shape maximises absorption of light
    • chloroplasts can move
    • vacuole full of H2O maintains cell turgor

  • striated or skeletal muscle

    • palisade cells have many chloroplasts to transport light energy for photosynthesis situated in the upper surface of leaf close to light
    • columnar shape maximises absorption of light
    • chloroplasts can move
    • vacuole full of H2O maintains cell turgor