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Classifying Animals 

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Animals are very diverse in which they do not have the same physical characteristics and behaviors that help them adapt and live in their environment. Despite their diversity, animals are known the have common ancestral characteristics which are evident based on Darwins theory of evolution. These shared and derived features for animals and their ancestors are linked together based on their Taxonomy. 

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Taxonomy 

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Taxonomy  the science dealing with description, identification, nomenclatures and classification of living things. This system of animal classification was developed by a naturalist named Carolus Linnaeus. Linnaeus's system of taxonomy has different levels that order animals from the broadest group to the most specific group. Within this taxonomy, organisms are separated into 3 main domains which are: Eukarya, Archaea, and Bacteria. 

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Archaea

Archaea are prokaryotic cells, typically characterized by membrane lipids that are bra chains attached to glycerol by ether linkages. 

Bacteria

Even though bacteria are prokaryotic cells just like Archaea, their membranes are made of unbranched fatty acid chains attached to glycerol by ester linkages. There is a lot of diversity in this domain, and between that and horizontal gene transfer, it is next to impossible to determine how many species of bacteria exist on the planet.

Eukarya

Members of the domain Eukarya have membrane-bound organelles (including a nucleus containing genetic material) and are represented by four kingdoms: Plantae, Protista, Animalia, and Fungi.

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Levels of Taxonomy 

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1. Kingdom- highest rank, grouping together all forms of life having certain fundamental characteristics in common

2. Phylum-grouping together all classes of organisms that have the same body plan

3. Class- organisms that contain general common traits, such as having a backbone, eight legs, etc. 

4. Order-a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes.

5. Family-a taxonomic group containing one or more genera

6. Genus-group of similar species that have similar features and are closely related. a taxonomic group containing one or more genera

7. Species- A group of closely related organisms that are very similar to each other and are usually capable of interbreeding and producing fertile offspring. The second word in the two-part naming system. It is always lower-case.

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 To display the evolutionary relationships between organisms, cladograms  are used. Within these  are used. Cladograms are diagrams which show the relationships between different groups of taxa called “clades”. By showing these relationships, cladograms reconstruct the evolutionary phylogeny of the taxonomy of organisms. 

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How to make cladograms :

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  1. Select a taxonomic group to be analyzed; for example, a group of vertebrates.

  2. For each member of the group, determine some observable traits (characters), and note their "states" (a "character state" is one of two [or more] possible forms of that character).

  3. For each character, determine which state is ancestral (primitive or plesiomorphic) and which is derived (apomorphic). This is done by comparing  more distantly related organism termed the "outgroup." I

  4. Group taxa by shared derived character states (synapomorphines). 

  5. choose a pathway that minimizes the number of times a feature must be postulated to have arisen (or lost) separately.

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Example of Cladogram 

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