Levels of organisation

Name the five hierarchical levels of organisation in multicellular organisms in order of size (cells, tissues, organs, organ systems, organism).
Define each level of organisation.
Provide examples of each level for both animal and plant.

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 Animal and plant cells and Specialised cells topics.

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.

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.

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.

Some of the organs and organ systems in the human body.

The fifth and highest level of organisation is a multicellular organism, which is made up of multiple organ systems working together to support life.
For example, humans are multicellular organisms composed of organ systems like the nervous, respiratory, and circulatory systems.

Multicellular organism: An organism made up of many cells working together.
Cells: The basic structural and functional units of life, the first level of organisation.
Tissues: Groups of similar cells that work together to perform a specific function.
Organs: Structures made up of different tissues working together to perform a specific function.
Organ systems: Groups of organs that work together to carry out major life processes.
Organism: A complete living being, the highest level of organisation, made up of multiple organ systems.

Choose a specific life process (e.g., digestion or gas exchange) and trace how different cells, tissues, organs, and organ systems contribute to that process in an animal.
Create detailed diagrams or models to represent the different levels of organisation, showing how they fit together in a plant or animal.