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The cell membrane is made up of something called the phospholipid bilayer. This is exactly what it sounds like:a hydrophilic phosphate head on the outside and a hydrophobic lipid on the inside. 

A synapse is a junction between the end of one neuron (known as the pre-synaptic neuron) and either another neuron (known as the post-synaptic neuron) or...

The respiratory system is a collection of organs working together in order to oxygenate the blood and remove the waste product carbon dioxide. The respiratory system uses a method of gaseous exchange ...

Evolution is a gradual change in the inherited traits of a population over many generations. 

Natural selection is a mechanism where the members of a population best suited to their environmen...