a tiny particle of matter

to pull closer

a row of connected bones down the middle of the back

A medicine that cures diseases by killing the bacteria that cause th

single-celled organisms that do not have a nucleus

a way in which a living thing acts or responds to its surroundings

a complete path for the flow of electric current

The smallest part of a living thing that can carry out all the processes of life

a covering that surrounds and protects a cell and controls what enters and leaves it

A vertebrate that lives part of its life in water and part on land

a stiff covering outside the cell

to sort things into groups according to their characteristics

a material that allows current to pass through it

an organelle in plant cells that uses light energy to make food.