As part of my learning experience, I am taking the useful advice someone offered and examining the many different tools available to learn more characters. To that effect, I am keying in the characters into a Mac using pinyin. I noticed that there are a number of visually related characters with different meanings. Is this a known phenomenon or just an unusual coincidence?
Some examples are:
I noticed that the differences are so slight (at least to my untrained eye) that one wonders about the glyph origins and how these visually related characters came to be. Is there a science to these visual relationships or are they random?
EDITS: Added to the examples with links to Chinese Etymology and Zhongwen images. However, I am still unsure of whether the development of the characters is related. I also plugged the characters into zdict.net but I am not competent enough to understand whether there is an explanation that might help me answer the main question: 天，夭，失，矢