In water molecule the electrons between the oxygen and the hydrogen are shared, but the sharing is not equal. Oxygen pulls electrons slightly towards itself. Therefore, the electrons are more near the oxygen, making that part of molecule(oxygen part) slightly negative. Since the electrons are not near the hydrogen so, that part of the molecule is slightly positive.
There are two types of succession that lead to the increasment of the ecosystem:
1. Primary succession is the change in the structure of an ecosystem represented with the increase of the ecological community on an area that has not been previously occupied by an ecological community such as area after the lava flow or glacial lake. The first organisms of primary succession are pioneer plants usually, lichens and mosses.
2. Secondary succession includes the step of removal of pre-existing community and after that, colonization of the new one.
AIDS attacks white blood cells, damaging the immune system and making the infected individual more susceptible to illness. White blood cells are the ones that fight off harmful bacteria, so without them you could even end up in the hospital or die from a common cold.
