The major functions of the nucleolus are that it is essential for spindle formation during nuclear division, it is the principal site for the formation of ribosomal RNAs, and it is the center for the formation of ribosomes. It also stores nucleoproteins. The classes of the phylum chordata are Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia. Magnification makes an object appear larger while resolution provides clearer, finer, and sharper images with more details. Transpiration is called a "necessary evil" because it controls water absorption and nutrient uptake but can also lead to water deficiency.