IB Biology D2.1 Notes

Now that you know nearly everything these is to know about cells, you need to understand how cells grow and divide, called cell proliferation. This is an important process in tissues for:

1. Tissue growth
2. Cell replacement
3. Tissue repair

In order to achieve this, cell undergo:

1. Stem cells specific to the tissue undergo mitosis to produce two identical daughter cells.
2. One of these remains a stem cell and the other differentiates into the specific cell type needed.
3. This thus adds new cells to tissue to increase tissue size, replacing lost cells, or both to replace injured/dead tissue.

You are expected to remember three examples of cell proliferation:

1. In apical plant meristem, stem cells undergo this process to add new cells to the root or shoot. This is thus cell proliferation for growth.
2. In early-stage embryos, stem cells undergo this process to develop and grow tissues and organs over time. This is thus also cell proliferation for growth.
3. In the skin, the top layer of cells regularly sheds or gets cut and injured. Thus, stem cells undergo this process to replace lost or dead cells. This is thus cell proliferation for routine cell replacement and wound healing.