Variation resulting from the appearance of mutations is called variation through mutation while that conditioned by subsequent recombination of genes as a result of interbreeding is called variation through recombination.roup variation includes the differences among aggregates of any rankâfrom differences among small groups of individuals within a population to differences among the kingdoms of living nature (animals and plants). In essence, the entire taxonomy of organisms is constructed on the comparative study of group variation.
The best known animal phyla are the Mollusca, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Echinodermata, and Chordata, the phylum to which humans belong.
Every organism can be classified at 7 different levels-kingdom, phylum, class, order, family, genus and species. Each level contains organisms with similar characteristics. The kingdom is the largest group and very broad. Each successive group contains fewer organisms, but the organisms are more similar.