A hypothesis is a testable possible explanation, while a theory is an explanation that has been tested extensively.
If you need to learn more and remember about this stuff better, watch the Amoeba Sister's <em>Casual and Scientific Use of "Theory" and "Law"</em>. Trust me, it helps!
:)I hope I answered your question well!:)
Living systems are open self-organizing life forms that interact with their environment. These systems are maintained by flows of information, energy and matter. Some scientists have proposed in the last few decades that a general living systems theory is required to explain the nature of life.
A extra genetic material at 21st chromosome i believe