(a) levels of organisation

organelle (2.1)

a component inside of cell that carries out a particular task e.g. cell membrane, mitochondrion

cell (2.1)

the basic functional unit of living organisms

tissue (2.1)

a collection of similar cells, carrying out a particular function within an organ

organ (2.1)

a collection of different tissues that work together to perform a common function e.g. heart, lungs, skin

system (2.1)

groups of organs working together to perform an overall function for the organism e.g. the nervous system, the circulatory system