The evolution of the two species are very closely related but not identical
Phospholipids have two distinct polarities. The phosphate head is always polar, while the two "tails" it has are nonpolar.
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Bacteria are helpful because they produce oxygen, which our bodies need to breathe, and they help us to digest the food we eat. Bacteria are also helpful because they are used in medicine to help us overcome disease. Bacteria are harmful because they can cause tooth decay and illnesses that can be either common or quite serious.
