A biome is a large naturally occurring community of flora (plants) and fauna (animals) occupying a major habitat (home or environment).

An ecosystem is a biological community of interacting organisms and their physical environment. This includes both the biotic (living) and abiotic (non-living).

An element is matter than cannot be separated into different types of matter by ordinary chemical methods.

An endoskeleton (internal skeleton) is a charateristic of vertebrate animals, including humans.

The two largest veins in the body, the venae cavae, pass blood to the right ventricle which pumps the blood to the lungs through the pulmonary artery. Blood picks up oxygen in the lungs and returns it to the left atrium via the pulmonary vein.