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I read article about apoptosis on Wikipedia, but didn't understand, how exactly the organism learns that it is necessary to launch process of apoptosis in certain cell. In other words, on what signs the cell is marked as "necessary to destroy"? How exactly at the chemical/biological level process of apoptosis starts?
Also I am misled by the fact that apoptosis occurs by a row of strongly differing reasons - not only aging, functionality losing, chemical/radiation affection, but also process of apoptosis can start in absolutely normal cells (including just newly created ones - for example, during formation of an embryo). How in that case the embryo knows what cells need to be destroyed, and how exactly it does it?

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closed as too broad by AliceD, MattDMo, kmm, James, WYSIWYG Sep 16 '16 at 5:56

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Unfortunately, this question is far too broad. From the help center: Your questions should be reasonably scoped. If you can imagine an entire book that answers your question, you’re asking too much. $\endgroup$ – MattDMo Sep 12 '16 at 13:39
  • $\begingroup$ Too bad for me. $\endgroup$ – Exerion Sep 12 '16 at 14:11
  • $\begingroup$ Maybe just evolution through chance-events and natural-selections helped them to adopt a self-destructive process? especially in multicellular forms? For an example, in plants, xylem (made mostly of dead-cells) was obtained probably because the death of some water-conducting cells (hydromes, as yet seen in bryophytes), made them empty, thus deceased friction and adhesion, that was advantageous. $\endgroup$ – Always Confused Sep 12 '16 at 19:44