Cell division

Seeds germinate into new plants.

We grow with age.

Cells get replaced on injured skin.

Cell division

• Cells increase in number by a

process called cell division.

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.

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.

Cell division

Mitosis

Meiosis

MITOSIS

PROPHASE TELOPHASE

METAPHASE ANAPHASE

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.

METAPHASE

0 The chromosome has two parallel strands called chromatids.

0 The chromatids are held together by centromere.

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.

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.

MEIOSIS

MEIO

SIS I

MEIO

SIS II

In sexual reproduction, the cell division process is known as meiosis.

SEXUAL REPRODUCTION

MEIOSIS I

PROPHASE I

METAPHASE I

ANAPHASE I

TELOPHASE I

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.

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.

Homologous chromosomes are pulled to

opposite poles of the cell.

In between the two sets of chromosomes

interzonal fibers are formed.

TELOPHASE I

Two daughter nuclei are formed.

Chromosomes have changed to chromatin network.

Nucleolus reappears.

Nuclear membrane reappears.

MEIOSIS II

PROPHASE II

METAPHASE II

ANAPHASE II

TELOPHASE 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.

PROPHASE II

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.

» Centromere of the chromosomes divides.

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

TELOPHASE II

Four daughter nuclei are formed.

Chromosomes have changed to chromatin network.

Nucleolus has reappeared.

Nuclear membrane has reappeared.

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.

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