Phylogeny is the study of the evolutionary history of groups of organisms, telling us who is related to whom and how closely they’re related. This can be demonstrated using a phylogenetic tree.

phylogenetic tree, beginner biology

The most closely related organisms diverged away from each other the most recently. In this case, bonobos are most closely related to chimpanzees.

Taxonomy is the science of classification, involving naming organisms and putting them into groups. There are eight groups used to classify organisms, Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species. These groups are arranged in a hierarchy, where there are groups within groups and no overlap. 

The naming system used to classify organisms is called the binomial system. The binomial name of an organism is just its genus and species. When writing the binomial name of an organism, The genus is capitalised and the name is underlined. For example, the binomial name is Homo sapiens. Don’t worry, you don’t have to remember any names, you only have to know how to write the binomial name if given the genus and species of an organism.

Scientists used to classify organisms by looking at their phenotypes and comparing them to the phenotypes of other organisms. Now, scientists compare the DNA base sequence of an organism, as well as the proteins that can be made, to other organisms. However, due to the degenerate nature of our DNA, it is better to compare DNA than proteins. 

Scientists can also use immunological evidence to see how closely two organisms are related to each other. This is done by:

1) First, you produce antibodies against the proteins of the organism you are comparing. 

2) Then you mix the antibodies with the other organism’s blood. This should form a precipitate.

3) The greater the precipitate produced, the more closely the organisms are related.   

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