As you can see, in the early days of classification only observable features were used. Today, scientists can take from a wider range of evidence to reach their conclusions.

Genetic comparisons

One way to compare species is by looking at their DNA or the proteins which the DNA codes for. One group of genes that has been popularly used are those that code for ribosomal RNAs.

DNA

Similarities in DNA can be observed through DNA hybridisation. By unzipping the DNA for two different species and allowing them to then mix scientists can see if there’s any complementary base paring. The more base pairing that takes place the more energy that’ll be required to separate the strands afterwards and so the higher the similarity between the species.

Look below for a summary of things to remember for you A level biology revision:

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REMEMBER IT!

• Scientists can compare species by looking at their DNA or the proteins which their DNA codes for.
• Similarities in DNA can be observed through DNA hybridisation.
• DNA hybridisation involves unzipping the DNA for two different species and allowing them to then mix scientists can see if there’s any complementary base paring.
• Comparisons can be looked for between amino acid sequencing.
• Immunological comparisons can be used in which blood from one species can be with mixed with another. Antigen-antibody complexes precipitate so the more precipitation, the closer the relationship.
• Courtship is a very important for mating and plays a big role in species recognition.