The nucleus of a eukaryotic cell contains the genetic material of the cell and is surrounded by cytoplasm which contains many organelles. These include:

After air enters through the nose, it passes through the nasal cavity which filters, moistens, and warms it. Further filtering takes place in the pharynx, which also helps protect against infection, and then in the trachea which is just past the epiglottis, responsible for preventing food from entering the airway.

The columns of the Periodic Table are called groups and all elements in a group have the same number of electrons in their outer electron shell. The group that an element occupies generally determines its chemical properties as the number of outer shell electrons establishes the way it reacts with other elements to form molecules. So, because each element has the same number of electrons in its outer shell, each has similar reactivity.

Small quantities of certain minerals like iron, calcium, magnesium, and salt are important for nutrition and health.

Secondary consumers (carnivores) subsist mainly on primary consumers. Omnivores are secondary consumers that also eat producers. Examples are rats, fish, and chickens.