In a polar covalent bond, the bonding pair of electrons in the bond are attracted more strongly to one molecule than the other. This means the electrons are pulled closer to one atom than the other. In the example of water, the electrons, in the hydrogen-oxygen bond, are more attracted to oxygen and therefore the electrons are drawn closer to the oxygen. This leads to a slightly negative charge on the oxygen and a slightly positive charge on the hydrogen.
An opposable thumb is a thumb that can be placed opposite the fingers of the same hand. Opposable thumbs allow the digits to grasp and handle objects and are characteristic of primates.
Opposable thumbs are one of the distinguishing features of primates. Opposable thumbs of human beings allow them to use tools.
