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

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