Mitosis and meiosis.

2. Seeds
We
germinate into new plants.
grow with age.
Cells
get replaced on injured skin.

3. Cell division
• Cells increase in number by a
process called cell division.

4.  There are two types of cells. They are :
1)Vegetative cells
2)Reproductive cells
 The cells which help in growth are called vegetative
cells.
 The cells that help in reproduction are called
reproductive cells.

5. In every cell, there are a few microscopic
structures in the cytoplasm. They are called
organelles.
 In cell division, centrioles and nucleus play
an important role.


6. Mitosis
Cell division
Meiosis

7. MITOSIS
TELOPHASE
PROPHASE
METAPHASE
ANAPHASE

9. PROPHASE
 Centrioles
have changed to star shaped
structures called asters.
 In between the asters, spindle fibers are
formed.
 Chromatin network has changed to
chromosomes.
 Nucleolus has disappeared, nuclear
membrane has disappeared.

11. METAPHASE
0 The chromosome has two parallel
strands called chromatids.
0 The chromatids are held together
by centromere.

13. ANAPHASE
 Chromatids of chromosomes have divided.
 Thus daughter chromosomes are formed.
 Daughter chromosomes are pulled equally to both
poles.
 This results in equal cells.
 The mother cell has same number of chromosomes
as daughter cells.

15.  Two
daughter nuclei are formed.
 Chromosomes have changed to chromatin
network.
 Nucleolus has reappeared.
 Nuclear membrane has reappeared.
Thus the cell divides into two new daughter
cells.

17. SEXUAL REPRODUCTION
In sexual reproduction, the cell division process is known as
meiosis.
MEIOSIS
MEIO
SIS I
MEIO
SIS II

18. PROPHASE I
METAPHASE I
MEIOSIS I
ANAPHASE I
TELOPHASE I

19. PROPHASE I
 Centrioles have changed to star shaped
structures called ASTERS. In between the asters,
spindle fibers are formed.
 Chromatin network has changed to
chromosomes.
 Paternal and maternal chromosomes have
pared with each other. The inner chromatids
have exchanged their segments with each other.
 Nucleolus and nuclear membrane have
disappeared.

21. 


Chromosomes are arranged at the center of
the cell.
Asters have moved to both poles of the cell.
Spindle fibers are attached to the centromere
of the chromosome.

23.  Homologous
chromosomes are pulled to
opposite poles of the cell.
 In between the two sets of chromosomes
interzonal fibers are formed.

25. TELOPHASE I
 Two daughter nuclei are formed.
 Chromosomes have changed to chromatin network.
 Nucleolus reappears.
 Nuclear membrane reappears.

27. PROPHASE II
METAPHASE II
MEIOSIS II
ANAPHASE II
TELOPHASE II

28. PROPHASE II

 Centrioles have changed to star shaped structures
called asters.
 In between the asters, spindle fibers are formed.
 Chromatin network has changed to chromosomes.
 Nucleolus has disappeared, nuclear membrane has
disappeared.

30. METAPHASE II
Asters have moved to all four corners
of the cell.
 Chromosomes are arranged at the
center of the cell.
 Aster fibers are holding the
centromere of the chromosomes.


32. » Centromere of the chromosomes divides.
» Daughter chromosomes are pulled equally to all
four corners of the cell.

34. TELOPHASE II
 Four daughter nuclei are formed.
 Chromosomes have changed to chromatin network.
 Nucleolus has reappeared.
 Nuclear membrane has reappeared.

36.  These
cells have only half the number of
chromosomes as that of their mother cell.
 These
cells are the reproductive cells that
take part in sexual reproduction.
 In
humans, the male reproductive cell is
called the SPERM and the female
reproductive cell is called the OVUM.

37. Thus cell division plays an important role in
growth, repair and healing of wounds and also
reproduction.