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  • Created by: harry
  • Created on: 09-01-12 20:41


Classification: the organisation of living organisms into grooups (taxa) according to their shared similarities.

Heirachical classification: placing organisms into a series of smaller and smaller groups, with no overlaps, between the groups.

Taxonomy: the study of principles behind classification. (the study of the differences between species eg: morphology, nutrition which are used place organisms in groups)

Phylogeny: is the study of evolutionary relationships between organisms. The more closely related two species are the more characteristics they have in common and more grouping they share. All species are desceneded from a common ancestors but more closely related two species are more recently they have shared an ancestor in common.

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Hierarchical phylogentic classification

organisms are classified into series of smaller and smaller groupings (taxa) based on their evolutionary history. The names of the taxa are DOMAIN KINGDOM PHYLUM CLASS ORDER FAMILY GENUS SPECIES. (Dad kills pretty cats of finland going smelly) Three domains: EUBACTERIA, ARCHAEBACTERIA, EUKARYOTAE. All eukaryotic organisms are in the domain eukaryotae. Prokaryotic organisms belong to the domain eubacteria or to the domain archaebacteria. There are five kingdoms: Prokaryota, protoctista, fungi, plantae and animalia.

The more taxa two species share the more characteristics they share and the more closely related they are.

The binominal system of naming species: Species are usually referred to by their genus and species name: for eg: humans are Homo sapiens. The genus starts with a capital letter and species in lower case. They are written in ITALICS. Sub species are groups within a species which have a distinct morphology. Eg: great Danes poodles.

They can still interbreed to produce fertile offspring.

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How species are classified.

Phylogenetic classification classifies species by their evolutionary history. This is determined by:

Tradionally organisms have been classified on the basis of observable homologuos featuresd such as how many legs the oraism has. More recent methods take into accoiunt molecular evidence such as: The type of nutrition (heterotroph or autotroph) the organism uses. Similarities of DNA nucleotide sequences in genes. the more similar the sequences are the more closelyrelated  the 2 species, more taxa they share. Genes are subject to occasional chance mutations. The more recently tewo species have diverged from a common ancestorthe fewer differences there will be between their dna sequences. Dna sequences/ genes cd for the sequence of amino acidsin proteins therefore analysing amino acid sequencs in proteins such as cytochromes also shows the evolutionary history of an organism; the more simliar the sequence the more closely related they are.

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Animalia: Eukaryotic cell. (linear chromosomes, enclosed in a nuclar membrane,memebrane bound organelles: mitrochrondiria, 80s ribs, No cell wall sexual reproduction, hetrotropic.

Plantae: Eukaryotic cell: linear chromosomes enclosed in nuclear membrane bound organeles: mitrochrondira and chloroplasts, cell walls: cellulose, (a)sexual reproduction, autotropic.

Fungi: Eukaryotic cell: (linear chromosomes enclosed in a nuclear membrane, bound organelles: mitrochrndira, asexual spores, hetrotropic.

Protoctista: Eukaryotic cell: linear chromosomes: enclosed in a nuclear membrane,: bound organelles: mitrochrondia, singled celled, mu;ti cellular.

Prokaryotae: cprokaryotic cell: (single circular chroose: naked not contained within nuclear enevlope. NO membrane bound organelles. 70s ribss. Asexual, hetrotropic.

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3 Domain classification system:

2 techniquies are developed: new discoveries are made, and science change views. Tradionally the classificatiion system had two domains, but now we have 3. This was because Carl Woese, studied RNA sequences: Animalia, Plantae, Fungi and Protoctista kingdoms are all within eukaryotae domain. 2 domains eubacteria and archaebacteria comprise prokaryota kingdom.

Archaea shared some features in common with eukaryotic and prokaryotic.

Dichotomous keys: are used by sciencetists to identify and name organisms. They comprise a series of yes and no questions.

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