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Section 2: Structures and functions in living organisms
a) Levels of organisation
2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems.

  • Organelles are tiny structures within cells
    • For example:
      • Nucleus
      • Cell membrane 
  • Cells can be specialised for a specific function
    • For example:
      • Red blood cells are adapted for carrying oxygen
  • Tissues are a group of similar cells that work together to carry out a specific function
    • For example:
      • Xylem and phloem tissues in plants
  • Organs are different tissues that work together to perform a function
    • For example:
      • Lungs
      • Leaves
  • Organ systems are organs working together
    • For example:
      • Digestive system (stomach, intestines, pancreas, liver)
b) Cell structure:
  • Nucleus - control cell's activities and contains genetic material
  • Cell membrane - controls substances that go in and out of the cell
  • Chloroplasts - contain chlorophyll for photosynthesis to happen
  • Cell wall - rigid structure made from cellulose (in plants), supports and strengthens the cell
  • Vacuole - contains cell sap and supports the cell 
  • Cytoplasm - chemical reactions happen here
Animal cells have a nucleus, cell membrane and a cytoplasm.
Plant cells have a nucleus, cell membrane, cytoplasm, chloroplasts, cell wall and vacuole.
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