In biology, the pH scale measures how acidic or basic something is. The lower the number, the more acidic while the higher the number means it is basic. A pH of 7 is neutral which is what the human blood pH is, more specifically around 7.35–7.45.

Charles Darwin is a scientist who coined the idea of natural selection – that animals who have the ability to adapt to their environment have a better chance at survival and reproduction.

Iron is the metal that is found in blood. It is very important in the transpiration process and helps transport oxygen throughout the body.

The femur is the longest bone in the body and can be found in the thigh. It begins at the pelvic bone and continues to the patella (knee).

The human genome should have a total of 46 chromosomes but 23 pairs. These pairs can determine things such as whether you're a male or female or whether you'll have any conditions or diseases.

DNA is essentially the genetic instructions of the human body. It is a code that, when analyzed, can be used to determine genetic traits. The acronym stands for deoxyribonucleic acid.

When it comes to single-celled organisms, they can either be a prokaryote or a eukaryote. The defining factor is that eukaryotes have a nucleus while prokaryotes do not.

Omnivore is the term reserved for an animal that eats both meat and plants with the prefix omni- meaning everything. A carnivore only eats meat, while herbivores only eat plants.

While blood type O is known as the universal donor, blood type AB is known as the universal receiver. This means that someone with blood type AB can receive blood from someone with blood type A, B, or O.

When a baby is born they have about 300 bones in their body. This is why they're so flexible. As they get older, their bones start to fuse together, and this becomes the 206 bones that the average adult has.