There are over 1.5 million species of animals on Earth and with such variety in their features and new species being discovered all the time. Scientists needed a way to distinguish between species and be able to group species with similar characteristics together. To solve these problem scientists began grouping animals into categories through sorting their similar characteristics and ancestry. This is called taxonomy.

Taxonomy has uses besides keeping species organized. Scientists in the field of taxonomy use classification to examine the relationship between fossilized animals that are extinct and modern animals. Through looking at fossils scientists compare features of classes. This allows them to see the similarities between different species or between a fossil and modern animal allowing scientists to see if it is possible that the animals are related or perhaps evolved from one another.

Scientists have developed many ways of looking at the relationships between animals. By looking at embryonic development, DNA, Immunology and Biochemistry relationships can be determined. They need many different ways of showing relationships because appearance is not always the best indication. For example the


Scientists believe that the development of the embryo reveals a lot about the relationship between organisms. This is because in the embryonic stage some embryos share similar characteristics but when they are older they can look completely different. Humans and monkeys look very similar as embryos and do not begin to take on different characteristics until the late fetal stage.

When scientists look at DNA to make links between species they compare strings of DNA taken from the nucleotide. A double helix of is spilt into two and one half from each species is bond together. How closely the species is related it then determined by the attraction between base sequences of the DNA. This is know as DNA hybridization.
DNA is used in the study of evolution, When trying to find a common ancestor the DNA from an animal can be taken from the mitochondria. Because the mitochondria pass from one generation to the next fromn the mother and they mutate at a certain rate, Scientists can measure how long ago evolution occurred and from which species a newer species came from.