Carbon dioxide exists naturally in the atmosphere as a result of the earth's carbon cycle. It is also there as a result of man's activities in burning fossil fuels (coal, oil â¦ and natural gas), which releases long-stored carbon dioxide to add to the greenhouse gases already there.
Credit for developing cell theory is usually given to three scientists: Theodor Schwann, Matthias Jakob Schleiden, and Rudolf Virchow. In 1839. I found this answer on examvillâ¦e.com, helped me complete my homework assignment.
Schleiden and Schwann came up with what is known as The Theory of  Cells or Cell Theory.. The main principles of Cell Theory are:    All cells come from cells  â¦  A cell is the basic unit of life   All organisms are made of cells   . + 59 others found this useful.