Does a unicellular organism like amoeba or yeast ever ‘grow old’? When it divides, it produces almost two identical copies. So, does aging happen at all?
Yes, unicellular organisms like amoeba or yeast do 'grow old' and experience aging. Every organism has a definite life span—it is born, grows, matures, reproduces, and eventually dies. This fundamental characteristic of living beings applies to unicellular organisms as well, meaning they too age and ultimately die.
These organisms reproduce asexually through a central process called mitosis. During this type of cell division, the parent cell divides to produce two daughter cells. Each daughter cell receives the same number of chromosomes, making them genetically identical to the parent cell.
Because the offspring produced are genetically identical to the parent, they are referred to as clones. While the individual parent organism ages and dies as part of its natural life span, its exact genetic material continues to exist in the newly formed clones.
This phenomenon is similar to how a mango tree may grow old and die, but its seeds continue to grow as new mango plants. Therefore, aging does happen in unicellular organisms, but life on Earth continues to exist as they reproduce identical copies of themselves before dying.
Explanation
The textbook context establishes that every organism, including unicellular ones, has a definite life span and eventually dies, which implies aging occurs. It also explains that unicellular organisms reproduce asexually via mitosis, producing genetically identical clones. By combining these concepts, students can deduce that while the individual organism ages and dies, its lineage continues through clones, much like a mango tree dies but its seeds live on.