explain this statement cell division occurs in certain tissues is replaced by lost cells
The correct statement should be: Cell division occurs in certain tissues to replace lost cells.
This statements means that in plants and animals the cell division occurs in particular tissues only to replace the cells lost due to injury, wear and tear or naturally.
For example,
In animals, the RBCs have life span of only 120 days after which they die. The new RBCs are produced in a particular tissue called bone marrow to replace these lost cells of blood.
In plants, cell division occurs in meristematic tissues only to replace cells lost in different parts of plant.
This statements means that in plants and animals the cell division occurs in particular tissues only to replace the cells lost due to injury, wear and tear or naturally.
For example,
In animals, the RBCs have life span of only 120 days after which they die. The new RBCs are produced in a particular tissue called bone marrow to replace these lost cells of blood.
In plants, cell division occurs in meristematic tissues only to replace cells lost in different parts of plant.