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.
In 1838 Schwann became familiar with Matthias Schleiden's microscopic research on plants. Schleiden described plant cells and proposed a cell theory which he was certain was the key to plant anatomy and growth. Pursuing this line of research on animal tissues, Schwann not only verified the existence of cells, but he traced the development of many adult tissues from early embryo stages.