The scientific classification of Old Man Cactus and Oat plant 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 Oat plant kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Old Man Cactus and Oat plant family is a major factor of Old Man Cactus and Oat plant 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 Oat plant belongs to the family Poaceae.
While comparing scientific classification, Old Man Cactus and Oat plant genus and other classification are also important. Also, when you compare Old Man Cactus and Oat plant, 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 Avena. Old Man Cactus tribe is Pachycereeae and Oat plant tribe is Aveneae. Old Man Cactus clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales whereas Oat plant clade is Angiosperms, Commelinids and Monocots and order is Poales. Every plant have subfamilies. Old Man Cactus subfamilies are, Cactoideae and Oat plant subfamilies are Pooideae. In this way you can compare scientific classification of Old Man Cactus and Oat plant and other products also.