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Topic 8- Classification
Taxonomy is a method of classifying living organisms. It can be analogous (based on function) e.g. all flying animals such as
birds, bats and insects; or homologous based on features that share the same underlying structure) e.g. vertebrates. We use
the homologous system because it shows evolutionary reflationary relationships.
Levels of organisation:
Kingdom- e.g. Anamalia
Phylum- e.g. Chordata (the sub-phylum is vertebrata)
Class- e.g. Mammalia
Order- e.g. Primates
Family- e.g. Hominidae
Genus- e.g. Homo
Species- e.g. Homo sapiens
There are 5 kingdoms:
Fungi (decomposers) - they are different from plants because they don't photosynthesise.
Algae and others.
Plants (green plants that contain chlorophyll and make food by photosynthesis.
Closely related species that share a common ancestor.
The species name always includes the genus e.g. all types of crow are Corvus so:
o Raven- Corvus corax.
o Carrion crow- Corvus corone.
o Hooded crow- Corvus cornix.
o Jackdaw- Corvus monedula.
A species is defined as: a group of organisms that have the same physical characteristic and interbreed to produce fertile
Biochemical Methods in Taxonomy
Evolutionary trees are used to determine how closely species are related.
They show that close relatives must have a recent common ancestor, which means that they must have similar genes and
therefore similar base sequences of DNA, which in turn means similar amino acid sequences on proteins. Likewise distant
relatives have a less recent common ancestor and there genes and therefore amino acid sequenced of proteins will be more
Method 1- Serum and Antibiotics
1. Rabbit injected with human serum- a mix of human proteins.
2. The rabbit makes antibodies against human proteins.
3. The antibodies are collected.
The antibodies are then added to serum. In an animal of the same species, all the serum will coagulate. In less related species
there is less coagulation because there are less identical proteins that will be coagulated by the matching antibodies.
Method 2- Primary Structure of Proteins
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The more closely related the organism is the more similar the genes, therefore the DNA base sequence is more similar and
the amino acid sequence of the proteins is more similar.…read more