Cells

• Cells are organised into groups
• A group of similar cells form a tissue
• Different tissues form an organ
• A group of organs that work together to perform a specific function is called an organ system.
• A multicelluar organism is usually made up of several organ systems.
• An example is:

  Palisade cells make up palisade tissue which with other tissues make up a leaf (organ!), and with many more leaves and other organs make up the shoot system. Various organ systems make up a full plant. (an organism)
• Cells need things like glucose and oxygen to survive.
• They also need to get rid of waste products, like carbon dioxide.
• These materials all move into or out of cells by a process called diffusion.
• Diffusion is where a substance moves from an area of high concentration to low concentration