What is cell wall???​

You can simply define the cell wall as a semi-rigid thick protective structure that surrounds the cell membrane of some types of cells for protection and defining the shape of the cell. The cell membrane alone cannot provide the required rigidity or strength. All living organisms are composed of cells.

A cell wall is a rigid layer of polysaccharides lying outside the plasma membrane of the cells of plants, fungi, and bacteria. In the algae and higher plants it consists mainly of cellulose. It provides the cell with both structural support and protection, and also acts as a filtering mechanism.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".