Growing by dividing
Cells stop at a size limit, so the body grows by making more cells.
Heal and grow
A cut on your skin heals in a few days. A child grows taller every year.
Does a body grow because each cell gets bigger and bigger?
What this lesson covers
The idea
Cells can grow only up to a certain size, so a body grows because cells divide to form new cells, which also replace old, dead or damaged cells; eukaryotic cells divide in an orderly way through the cell cycle.
Heal and grow
A cut on your skin heals in a few days. A child grows taller every year.
Does a body grow because each cell gets bigger and bigger?
- No. Cells can grow only up to a certain size, so the body grows by making new cells
- Yes. Cells keep growing without limit
- No. The body grows because water is added
Two ways to grow
Compare the two ways. Run time forward each time.
Cell division
Cells can grow only up to a certain size. The body grows because cells divide to form new cells, which also replace old, dead or damaged cells. Eukaryotic cells divide in an orderly, controlled way through the cell cycle.
Every day, hundreds of billions of cells in the human body are replaced: about 1 per cent of all our cells.
- Event | Why it happens
- A cut heals | cells divide to replace damaged cells
- Hair grows back | new cells replace those lost
- A root tip grows | its cells divide continuously
Notes
Cells can grow only to a certain size, so a body grows when cells divide to make new cells. Division also replaces old, dead or damaged cells.
Check yourself
Why does the body grow?
Which of these is not a reason for cell division?
Cells of a growing onion root tip…
About 1 per cent of our cells are replaced every day. Out of 100 cells, how many is that?
Answer: 1
1 per cent of 100 is 1.
- Cells divide to form new cells — correct. Yes.
- Each cell grows without limit. Cells can only grow up to a certain size.
- Cells get smaller. Division adds cells.
- To make a cell wall stronger — correct. Not named. Division is for growth and for replacing cells.
- To grow the body. It is a reason.
- To replace dead cells. It is a reason.
- To repair damaged cells. It is a reason.
- divide continuously — correct. Yes.
- never divide. They divide continuously.
- die at once. They divide continuously.