1. Cell Division and Fertilization
KS4 Biology
Cell Division
and Fertilization

2. Cell Division and Fertilization
Contents
Cell Division and Fertilization
Introducing cell division
What is mitosis?
Chromosomes and fertilization
What is meiosis?
Mitosis or meiosis?

3. How many cells? An adult human is made up of about 50 billion cells.
That’s cells!
Everyone started out as just one single cell.
How does one cell become 50 million million?

4. …mitosis and meiosis. Cell division Growth and repair of body cells.
New cells are produced by old cells dividing.
Why are new cells needed?
Growth and repair
of body cells.
Production of
specialized sex cells.
New cells are needed for two main reasons, so there are two different types of cell division…
…mitosis and meiosis.

5. Cell division and genetic information
Cells don’t just split in half when they
divide. If they did, there wouldn’t
be much of the cells left!
It is essential that the genetic
information carried in a cell
is transferred to the new cells.
Where is genetic information
carried in a cell?
When a cell divides how can this genetic information
be transferred without any of it being lost?

6. Cell division and chromosomes
Chromosomes in the nucleus carry the genetic information of a cell.
Chromosomes must be accurately copied and passed on during
cell division.
This is important to make sure
that no genetic information is lost.
Knowing about chromosomes and what happens to them during cell division is the key to understanding the differences between mitosis and meiosis.

7. Cell Division and Fertilization
Contents
Cell Division and Fertilization
Introducing cell division
What is mitosis?
Chromosomes and fertilization
What is meiosis?
Mitosis or meiosis?

8. What is mitosis?
Mitosis begins with a single cell. How many chromosomes does this cell contain?
original cell
First the cell makes a copy
of each chromosome…
…then it divides.
cell division
Each new cell has a full set of chromosomes and is identical to the original cell.
2 new cells

9. What is mitosis? Each new cell can keep on dividing by mitosis.
Mitosis makes new cells for growth and repair in all living things. That’s how you get
from one cell to 50 billion!
Mitosis is also called
copying division.
What does this mean?

10. Mitosis activity

11. Mitosis animation

12. Mitosis summary
How does mitosis turn one cell into two new cells?

13. Stages of mitosis activity
Teacher Notes
The correct order of the stages of mitosis is:
1. D, 2. F, 3. A, 4. G,
5. E, 6. C, 7. B, 8. H.

14. Cell Division and Fertilization
Contents
Cell Division and Fertilization
Introducing cell division
What is mitosis?
Chromosomes and fertilization
What is meiosis?
Mitosis or meiosis?

15. How many chromosomes?
How many chromosomes are there in each new human body cell produced by mitosis?
46 chromosomes
(23 matching pairs)
How many chromosomes are there in human sex cells?
23 unpaired chromosomes
23 unpaired chromosomes

16. How many chromosomes?
Human sex cells have a set of 23 unpaired chromosomes – that’s half the usual number.
Sex cells in animals and plants follow the same rules.
They have half the usual number of chromosomes.
They have a complete set of single chromosomes.
Why is this important for fertilization and reproduction?

17. Fertilization animation
FLASH 6 – Fertilisation
FLASH 2 – Mitosis drag & drop

18. Chromosomes and fertilization

19. Sex cells and cell division
Sex cells have half the usual number of chromosomes.
Why aren’t new sex cells produced by mitosis?
Sex cells have to be produced by a special type of cell division. This is why there are two types of cell division.
Sex cells are produced by meiosis.
In which organs does meiosis take place?

20. Cell Division and Fertilization
Contents
Cell Division and Fertilization
Introducing cell division
What is mitosis?
Chromosomes and fertilization
What is meiosis?
Mitosis or meiosis?

21. What is meiosis? Meiosis begins with a single cell. original cell
First the cell makes a copy
of each chromosome.
first
division
Now, there are two stages of cell division…
second
division
How many chromosomes do the new cells have compared to the original?
4 new cells

22. What is meiosis?
Meiosis produces four new sex cells with half the original number of chromosomes.
In animals, meiosis produces ova in females and sperm cells in males.
In plants, the gametes produced by meiosis are pollen grains and ovules.
Mitosis is also called reduction division.
What does this mean?

23. Meiosis activity

24. Meiosis animation

25. Meiosis summary
How does meiosis turn one cell into four new sex cells?

26. Stages of meiosis activity
Teacher Notes
The correct order of the stages of meiosis is:
1. E, 2. D, 3. G, 4. F,
5. A, 6. C, 7. H, 8. B.

27. Cell Division and Fertilization
Contents
Cell Division and Fertilization
Introducing cell division
What is mitosis?
Chromosomes and fertilization
What is meiosis?
Mitosis or meiosis?

28. Mitosis or meiosis?

29. Who wants to have a million cells?
FLASH 2 – Mitosis drag & drop