The respiratory system manages respiration which is the process by which blood cells absorb oxygen and eliminate carbon dioxide.

Hard bones provide primary support for the endoskeleton while more flexible cartilage is found at the end of all bones, at the joints, and in the nose and ears. In addition to providing support and protecting bodily organs, bones also produce blood cells and store minerals like calcium.

The cerebrum is the major part of the brain and is responsible for the main senses (thinking, hearing, seeing).

Cells are classified into one of two groups based on whether or not they have a nucleus. Eukaryotic cells have a nucleus, prokaryotic cells do not have a nucleus and therefore have a less complex structure than eukaryotic cells.

An electron is a subatomic particle that orbits the nucleus of an atom. It carries a negative electric charge. Generally, an atom has the same number of negative electrons orbiting the nucleus as it does positive protons inside.