Means of Classification

Means of Classification

1. Phylogeny

   • This is the classification of organisms depending on their evolutionary history.
     • A phylogenetic tree is used to represent organisms of different species and how closely they are related.
       • The closer they are, the more related they are, in terms of the ancestor species they have evolved from.
   • For example, humans are closely related to the orangutan and chimpanzee, as they are next to each other the phylogenetic tree.
     • This means that these three organisms must have evolved from the same species.

2. taxonomy

   • This is the science of naming organisms.
     • There are 8 levels of classifying organisms, each one known as a taxa.
       • The whole thing is known as hierarchy which means groups within groups with no overlaps.
         • The 8 groups are: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
   • Organisms are named using their genus (begins with capital letter), followed by their species (all small letters.
     • For example, Homo sapiens (humans).
       • 'Homo' is the genus and 'sapiens' is the species, of humans.

3. Courtship behaviour

   • This is the behaviours of organisms to attract a mate of the same species.
     • As different species have different courtship behaviour, this can be used to classify organisms.
     • It prevents the mating of wrong organisms, of different species.
     • It also allows breeding to occur between organisms of the same maturity, e.g. not too young or too old.
   • There are two types: simple and complex.
     • Peacocks use their feathers as an attractive visual display. This is simple.
     • The blue-footed booby does a complex dance routine.
     • The male red deer simply makes a loud noise.

4. Using DNA

   • During this, the DNA of certain organisms can be extracted.
     • Then the genome (the full set of DNA bases) can be compared.
       • The less differences there are between the two strands, the more closely related the two organisms are.
   • You can also compare the amino acid sequence of two organisms protein.
     • The more similar they are, the closer they are related.

5. Immunological comparisons

   • This is simply comparing the antibodies of two different organisms.
     • This is done by using an antigen and seeing whether they bind to form an antigen-antibody complex.
       • If they both do, the organisms are related.

6. Biodiversity

   • This is the number of different organisms on Earth, as well as the genetic variation between them.
   • Farmers reduce the biodiversity of crops making it difficult to classify, by using selective breeding instead of natural selection.
     • Natural selection is when organisms naturally select features which help it to survive pass it on to  the next generation. 
     • Selective breeding is when humans deliberately choose a feature that will benefit them, and make them breed. THIS MAY NOT HELP WITH SURVIVAL!
     • They use pesticides which kill insects.
     • They use fertilisers which flow into rivers through desertification, killing fish.
     • They use monoculture, which supports fewer organisms.
       • Monoculture is the growing of only one type of crop only.
     • They cut bushes and hedgerows, destroying habitat.