Levels of organisation

• Multicellular organisms are made up of many cells that work together to carry out life processes. In multicellular organisms, there are various levels of organisation, forming a hierarchy. 

• Cells are the building blocks of life, and the first level of organisation. 

• Examples of cells in animals are nerve, muscle, and red blood cells.

• Examples of cells in plants are root hair and leaf cells.

• More information about cells can be found in Cells topic.

Tissues

• The second level of organisation is tissue. A tissue is a group of similar cells that work together to perform a specific function.

• An example of a tissue in animals is muscle tissue, which allows muscles to contract and move parts of the body.

• An example of a tissue in plants is xylem, which transports water around the plant.

Organs

• The third level of organisation is an organ. An organ is made up of different tissues working together to perform a certain function.

• Examples of organs in animals are the heart, brain, and lungs.

• Examples of organs in plants are the roots, stems, and leaves.

Organ systems

• The fourth level of organisation is an organ system. An organ system is a group of organs working together to carry out major life processes.

• Examples of organ systems in animals:

• Circulatory system: Transports materials such as oxygen and nutrients around the body.

• Respiratory system: Takes in oxygen and removes carbon dioxide.

• Reproductive system: Produces offspring.

• In plants, flowers are part of the reproductive system.

Some of the organs in the human body.

Multicellular organisms