
What do you have in common with a shark, a zebra, and a pine tree? All four of you are alive - and so all four of you are made up of cells. Cells perform amazing functions. An animal's muscle cells contract and expand in response to signals they receive from nerve cells, allowing...

There are a number of key concepts that make up the core of science, such as cells, evolution, photosynthesis, and DNA. Often one key concept is an important part of others. for example, photosynthesis directly affects food chains, and food chains help determine the path of evolution...