Takes place by cell plate formation because constriction is not possible due to presence of the rigid cell wall.

`->` Many golgi vesicles and spindle microtubules arrange themselves on equator to form phragmoplast. Fragementes of ER may also deposit in phragmoplast.

`->` Membrane of golgi vesicles fuse to form a plate like structure called cell plate .

`->` Golgi vesicles secret calcium and magnesium pectate. Further cell plate is modified into middle lamella.

`->` In plants, cytokinesis occurs in centrifugal order {cell plate formation is from center to periphery).

1. Development of an organism occurs by mitosis. Every organism starts its life from a single cell i.e. zygote. Repeated mitosis in zygote leads to the formation of the whole body.

2. The growth of multicellular organisms is rlue to mitosis.

3. Cell growth results in disturbin~1 the ratio between the nucleus and the cytoplasm. It therefore becomes essential for the cell to divide to restore the nucleo-cytoplasmic ratio.

4. A very significant contribution of mitosis is cell repair. The cells of the upper layer of the epidermis, cells of the lining of the gut, and blood cells are being constantly replaced.

5. Mitotic divisions in the meristematic tissues- the apical and the lateral cambium, result in a continuous growth of plants throughout their life.

1. Cryptomitosis or Promitosis : l1 is a primitive type of mitosis. In this type of division, nuclear membrane does not disappear but remain intact throughout the division. All the changes of karyokinesis occurs inside nucleus even the formation of spindle (Called as intranuclear spindle) Such division is found in some protozoans (Amoeba) during binary fission.

2 Dinomitosis :- Dinomitoss is founds in dinoflagellates, which are mesokaryotes. In mesokaryotic cells histones are absent. Because of this, the chromosomes fail to condense properly and hence are not distinctly visible during cell division. Nuclear membrane persists throughout the cell division and spindle is intranuclear type.

`->` Normal mitosis is termed as Eumitosis.

3. Free nuclear division :- Karyokinesis is not followed by cytokinesis as a result of which multinucleated r'rwvmir;n arises. eg. endosperm.

4. Endomitosi~� :-This is duplication of chromosomes without division of nucleus. Endomitosis leads to polyploidy i.e. Increase in number of genome. Colchicine induces polyploidy in plants. Colchicine is a mitotic poison as it arrests the formation of spindle fibres.

5. Endoreduplication : Endoreduplication is a modification of endomitosis. The polytene chromosomes form by process of endoreduplication. In endoreduplication, the chromatids replicate but do not get seperated . This process is also known as polyteny .

`->` Mustard gas and Ribonucleases are also mitotic poisons.

"Term meiosis" was proposed by Farmer and Moore.

The specialised kind of cell division that reduces the chromosome number by half result in the production of haploid daughter cells. This kind of division is called meiosis.
Meiosis ensures the production of haploid phase in the life cycle of sexually reproducing organism whereas fertilisation restores the diploid phase. In meiosis during gametogenesis in plants and animals, leads to the
formation of haploid gametes.
Gametes are formed from specialised diploid cells.

# Meiosis involves two sequential cycles of nuclear and cell division called meiosis `I` and meiosis `II` but only a sinqle cycle of DNA replication .

`->` Meiosis I :-
lleterotypic division or reduction division. It leads to reduction in chromosome numbers. Division of chromosome does not occurs in meiosis land only segregation of homologous chromosomes (Bivalent) takes place.

# Meiosis I is initiated after the parental chromatids have replicated to produce identical sister chromatids at the S phase.

# Meiosis I involves pairing of homologous chromosomes and recombination between them .

`->` Meiosis II :-

This is a homotypic division or equalional division. It docs not leads to any change in chromosome number.

# Meiosis II is just like mitosis. Division of centromere occurs durinq meiosis II.

# Four haploid cells are formed at the end of meiosis II. All the four dougther cells produced by meiosis are generically different from each other and also differ frorn the mother cell.

# In meiosis. division of nucleus takes place twice but division of chromosome occurs only once. Meiotic events can be grouped under the following phases :

same as in mitosis