One of the changes in development and specialization that did not happen in primitive mammals was the increase in stomach capacity. The specialization of teeth and the lower jaw are two important modifications of the primitive mammals. Also an increase in size and brain capacity are two crucial modifications of the early mammals.
A plant cell contains a large, singular vacuole that is used for storage and maintaining the shape of the cell. In contrast, animal cells have many, smaller vacuoles. Plant cells have a cell wall, as well as a cell membrane. ... Animal cells simply have a cell membrane, but no cell wall.
