Classification and Evidence

Hiya,

Classification is the arrangement of organisms into groups on the basis of shared factors; this is done hierarchically.

Taxonomy is a form of classification where organisms are classified based on their anatomical features and physical similarities; for an ease of naming species

Carl Linneas was the first known scientist to try and classify organsisms where he suggested 2 domains; plants and animals. Later it was shown to be not so accurate and Carl Woese suggested 3 domains ( archaea, eukaroyta and bacteria) and 6 kingdoms falling under these domains (eubacteria, archae, protista, fungi, plantae and animalia. (Note that the Archaea domain is split into two kingdoms; archae, which are bacteria that can live in extreme conditions, and eubacteria, which are able to photosynthesise.

(Luca Basali)

To name species, we use binomial naming. This is done in latin as it's universal so is used by the entire world, this allows easy communication between scientists. Binomial naming starts with the Genus and is followed by the species. The genus must start with a capital letter and the species must start with a lower case letter. For example, Homo sapiens (modern humans). Remember; a species is a group of similar organisms that have features in common and that can reproduce to produce fertile offspring.

So what does the hierarchy look like?

In order to show this is true, evidence is needed. There are a few types of evidence;

• B- Biochemical; using biochemistry, we can look at genetics and biological molecules within an  organism and compare it to another organism. DNA is commonly used as evidence for classification; the more similar the DNA sequences of different organisms, the more alike they are and the closer related they are. If you think about it, the more similar the DNA sequence, the genes will be similar causing similar proteins to be produced therefore metabolic processes are more likely to be similar. Also, it's important to know about Cytochrome C. It's used in aereobic respiration in most living organisms and made from a small sequence of amino acids. The more similar the sequence of amino acids, the closer related the organisms are likely to be.

• E- Embryological; by studying embryos of different organisms, you can see similarities between offspring at different stages of pregnancy. Also, some organisms reproduce using eggs rather than in the womb; this is significant.

• A- Anatomical; structural similarities are called homologies. They show structures  that were present in a common ancestor. The more common homologous structures, the closer related two species are.