(a) levels of organisation

organelle

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

cell

the basic functional unit of living organisms

tissue

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

organ

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

system

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