Here is a crude concept map showing the relationships between the parts in terms of functions. I mentioned above that the smallest plants consisted of single cells. The largest organism on our planet is the sequoia tree. Certain fungi in soil, however, consist of microscopic but connect filaments of cells originating from a single spore. These fungi are basically invisible, but DNA evidence suggests that single individuals may spread across hundred of acres of land.
Some multicellular organisms can live to be very old.
The oldest documentable living organism is the bristlecone pine tree. These trees are frequently more than 5000 years old. These plants, still alive today, were already 3000 years old when Jesus walked through Jerusalem. Meristematic Cells undergo mitosis and thereby produce all cells of the plant body. Mitosis is a process in which a cell goes from interphase, through prophase, metaphase, anaphase, and telophase, and ends up in interphase again.