First, you're question is very vital, there are many ways in classifying along with identifying all living organisms that includes; morphological analysis, molecular systematics (studying the similarities and differences of the genetic data such in the sequences of DNA, RNA, and rRNA ), homology, cladistics, etc. based on phylogenetic tree, which the study of the evolutionary among various species.
But through it said that all living organisms shared one common ancestor. However, what makes them different from one to another is the homeotic genes that called <em>Hox </em>Genes; which specify the fate of a particular segment or region of the body, meaning the number and arrangements of the<em> Hox</em> genes varies considerably among different types of animals.
For instance, Sponges have at least one homologous to<em> Hox</em> genes, also insects have nine or more <em>Hox </em>genes resulting in multiple <em>Hox </em>genes occur in a cluster in which the genes are close to each other along a chromosome. Therefore, increases in the number of<em> Hox</em> genes have been instrumental in the evolution of many animals species with greater complexity in body structure.
Overall, more <em>Hox</em> genes, more complexity in body structure resulting in the differences of their morphological structure.
There are some who can't perceive the order of red and green together. Having it angled up and down is safer because you know out of common sense that red is on top and green is on the bottom. Having it sideways makes the light elevated on the same level, deceiving the eye better.
on-native species can become such a common part of an environment, culture, and even diet that little thought is given to their geographic origin. For example, soybeans, kiwi fruit, wheat, honey bees, and all livestock except the American bison and the turkey are non-native species to North America.
The similarities between bones of humans and other animals shows that every living creature on earth has a common ancestor, even if that common ancestor is as simple as a sing-celled organism.
