Due to the linneaus system of classification scientist were able to identify organism name , group via standardized system . They have found similarities in the organism like DNA / RNA ( genetic composition), embryonic development etc . so that they can study a organism completely . With the help of this system of classification scientist were able to give a particular name to a organism which is standardrized in the whole universe. It makes easier to all to identify an organism , otherwise different places have different name for a particular species.
Modern day whale species, have very small pelvic bones in comparison to their body size, and also they are useless. This is because this bones in the whale body are remnants from the time when their ancestors were land dwelling creatures, thus they had legs as the typical land mammal has. But during their evolution, as their ancestors were starting to adapt more to the water, the legs started to disappear, but the bones inside of the body remained, even though they were of not use. Even though millions of years had passed since this bone is useless, it still exists, and the reason for that is that there hasn't been any evolutionary pressure for it to not exist, since it is not causing any disadvantage into the movement and lifestyle of the whales.
You need larger amounts of macrominerals. They include calcium, phosphorus, magnesium, sodium, potassium, chloride and sulfur. You only need small amounts of trace minerals.