Theory- is a system of ideas intended to explain something or a phenomenon. For example, Darwin’s theory of evolution. Theory is built upon one or more hypothesis and upon evidence. A theory contains reasoning and logical connections that lead to certain conclusions. Theories can change based on new evidence. Can you think of theories that your teachers used in different subjects during your secondary education? For instance, the plat tectonic theory which explains landmass motion to form continents; the newton’s theory of gravity; the cell theory of organisms etc.