Organisation in Multicellular Organisms

Multicellular organisms, such as plants and animals, are organised into highly complex and structured systems. The order from least complex to most complex is:

  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organism



Cells are the basic structural and functional unit of a living organism. They are specialised to carry out specific functions.


Tissues are groups of cells with similar structures that work together to perform a shared function. For example, muscle tissue is a group of muscle cells that work together to contract and relax. This leads to movement at a joint.

Examples of tissue include:

  • Muscles
  • The blood
  • Xylem (Water carrying tubes in plants)
  • Nervous tissue


The organ structure is made up of a group of tissues, which work together to perform specific functions. For example, the heart contains fibrous tissue that makes up the heart valves and muscle tissue to pump the blood.

Some examples of organs are:

  • Kidney
  • Stomach
  • Lungs
  • Brain

Organ systems

An organ system is a group of organs with related functions that work together to perform bodily functions. For example, the circulatory system is responsible for pumping and circulating blood around the body. It includes the heart and blood vessels.

Some examples of organ systems are:

  • Skeletal system
  • Respiratory system
  • Muscular system
  • Circulatory system
  • Digestive system
  • Nervous system


An organism is made up of several organ systems that perform the processes required for life.

Organisation in plants

1. There are a lot of specialised plant cells that come together to form different plant tissues.

  • For example, the epidermal tissue form the xylem and phloem tubes

2. The different plant tissues come together to form organs.

  • The leaves, roots, and stem are all examples of plant organs

3. These organs come together to form organ systems.

  • An example of an organ system is the plant’s reproductive system, which allows a plant to produce new plants

4. These organ systems work together to form the organism, which is the entire plant in this case.