1) The study of fossils is called paleontology, and it helps us understand the history of life on Earth and the process of evolution.

2) The ozone layer, located in the Earth's stratosphere, protects us from harmful ultraviolet (UV) radiation.

3) The legislative branch in many democracies is responsible for making laws, representing the interests of the people, and providing checks and balances on the executive branch.

4) The concept of 3D printing, also known as additive manufacturing, was first introduced in the 1980s and has since revolutionized prototyping and small-scale production.