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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.
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
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.
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.