Giraffes probably used to have short necks. Over time, since the branches of trees or plants were out of their reach, they adapted to this by having a longer neck. Those with longer necks are able to reach the food and eat it that those with short necks could not. Obviously, those with longer necks are able to survive and therefore reproduce. Because of reproduction, they are able to pass on this characteristic that allowed them to survive on to their offspring. This leads to offspring doing the same and over time, affecting the entire population of giraffes and soon evolving giraffes. This is natural selection doing its work in the evolution of long necks in giraffes.
Mitosis. It is as well as meiosis, sometimes called the two nuclear division processes. Is this helpful?
Explanation:
Photosystems are the practical components for photosynthesis, well-defined by a specific stain association and connotation patterns, whose work is the absorption and allocation of light energy, which suggests transfer of electrons. Physically, photosystems are initiate in the thylakoid membranes. A photosystem consists of a light-harvesting complex and a reaction center. Pigments in the light-harvesting complex pass light energy to two special chlorophyll a molecules in the reaction center. Photosystem I or PS I and Photosystem II or PS II are the protein-mediated complex, and the main aim is to produce energy (ATP and 
), which is used in Calvin cycle, the PSI uses light energy to convert NADP+ to .
