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explain the 4 needs of cell division? differentiate between the mitosis in plants and in animals?with the help of diagram. significance of mitosis? define cell cycle with the help of a diagram?

The major differences in plant and animal cell division are in the assembly of the spindle apparatus. The site of spindle apparatus assembly is the centrosome. In animal cells, a pair of centrioles is at the center of the centrosome. In contrast, most plants lack centrioles, but they do have a centrosome. In animal cells, a cleavage furrow forms during cytokinesis, which deepens and then pinches the parent cells in two. Plant cells, which have cell walls, do not have a cleavage furrow. Instead, a cell plate is produced in the middle of the parent cell, which grows toward the perimeter of the cell until it reaches the plasma membrane, dividing the cell in two. A new cell wall then forms from the cell plate.

The significance of Mitosis are :-
1. It is an equational division through which identical daughter cells are produced having the same amount and type of genetic constitution as that of the parent cell.
2. It is responsible for growth and development of multi-cellular organisms from a single-celled zygote.
3. The number of chromosomes remains the same in all the cells produced by this division. Thus, the daughter cells retain the same characters as those of the parent cell.
4. It helps the cell in maintaining proper size.
5. Mitosis helps in restoring wear and tear in body tissues, replacement of damaged or lost part, healing of wounds and regeneration of detached parts (as in tail of a lizards).
6. It is a method of multiplication in unicellular organisms.
7. If mitosis remains unchecked, it may result in uncontrolled growth of cells leading to cancer or tumour.

The cell cycle is the life cycle of a dividing cell. It includes Interphase and the M phase or Mitotic phase (mitosis and cytokinesis).