2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems

The level of organisation is as follows (from smallest to largest)...

Organelles, cells, tissues, organs, organ systems

Organelles - they are highly organised structures of molecules that have a specific function within a cell. An example is mitochondria, their function is to generate energy for our bodies cells.

Cells - they are made up of organelles, described as a functional unit. Cells are the basis of living things. An example is a skin cell.

Tissues - tissues are a collection of similar cells that all serve a common function. An example is glandular tissue, which produces substances such as enzymes and hormones.

Organs - they are made up of several kinds of tissues that act together to form a functioning unit. An example its the heart.

Organ systems - systems are a group of several organs, for example the cardiovascular system is made up of the heart, blood and blood vessels.