The scientific classification of Old Man Cactus and Citrus includes the entire classification chart that includes kingdom, family, clade, tribe etc. A kingdom is the second highest taxonomic rank. A taxonomic rank is the level that a living organisms are placed in hierarchical level of arrangement of life forms. All the living organisms are divided into kingdoms. Plant kingdom is a main classification of living organisms that include all plants. There are six kingdoms which are: Plantae, Animalia, Fungi, Protista, Aschaea/Archaeabacteria and Bacteria Eubacteria. Old Man Cactus and Citrus kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Old Man Cactus and Citrus family is a major factor of Old Man Cactus and Citrus Scientific Classification. Plant family helps you narrow the search of your plants. It also gives you idea about, how the plant looks, how the seed will be like etc. These two plant families can be different or same. Old Man Cactus belongs to the family Cactaceae and Citrus belongs to the family Rutaceae.
While comparing scientific classification, Old Man Cactus and Citrus genus and other classification are also important. Also, when you compare Old Man Cactus and Citrus, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Cephalocereus and other plant's genus is Citrus. Old Man Cactus tribe is Pachycereeae and Citrus tribe is Citreae. Old Man Cactus clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales whereas Citrus clade is Angiosperms, Eudicots and Rosids and order is Sapindales. Every plant have subfamilies. Old Man Cactus subfamilies are, Cactoideae and Citrus subfamilies are Asteroideae. In this way you can compare scientific classification of Old Man Cactus and Citrus and other products also.