Natural: Land mounds, Rivers
Human made: Country borders, cities
The plasma membrane<span> is the boundary between the cell and its environment. It regulates what enters and exits the cell. Cells must maintain an appropriate amount of molecules to </span>function<span> inside them. They must also have a way to keep things out or to allow things to enter.</span>
Answer:
18 grams
Explanation:
Because 17,190 yrs divided by the amount of years it takes for a half-life to occur is 3. So 3 half life’s happen, so you divide 144/2 once, equaling 72. You divide 72/2 again (another half-life) and you get 36. You then calculate the third half life by dividing 36/2 which equals 18 grams.
Answer:
See the answer below
Explanation:
There are several scientists that contributed to the understanding of the cell. Some of them and their contributions are as follows:
Anton van Leeuwenhoek: He invented the first primitive microscope and was able to view some unicellular microscopic cells such as protozoans and bacteria. He disproved the theory of spontaneous generation by his discoveries.
Robert Hooke (1665): He improved further on the microscope invented by Leeuwenhoek and was able to view compartment-like rooms when tissues of cork were sectioned. He tagged the compartment as 'cell'.
Schleiden (1804–1881): Using an improved microscope, he was able to extensively study plant tissues and borrowed the word coined by Hooke (cell) to describe the component of the plant tissues.
Theodor Schwann (1810–1882): He studied animal tissues and made a similar observation as Schleiden.
Through their various studies, Schleiden, Schwann, and another scientist, Rudolf Virchow later developed what is nowadays known as the cell theory
