·        All the organisms that have cells containing true nuclei.  This domain includes many groups of single-celled organisms as well as multicellular plants, fungi and animals. [2]

·         They have bilateral symmetry and considered to be deuterostomes.  Chordates have a notochord; a dorsal, hollow nerve cord; pharynx geal slits or clefts; and a muscular, post-anal tail at some point throughout development. [2]

·         Mammals have a mammary gland, which produces milk  for offspring.  They are endothermic, have prolonged parenting to teach young survival skills, differentiated teeth, and most have a high metabolic rate. [2]

·         Rodents have continuously growing incisors that need to be worn down by gnawing.  They are primarily herbivores and generally small. [2]

·         Refers the Old World rats that are now dispersed around the world; they are distinguished from the Cricetidae due to the lack of cheek pouches. [1]

·         They can be described as a common house rat that has bevel edged incisors. [1]

·         It can be described as a common house hold rat that is known for being a pest. [1]

Copyright © 2004-2012 Free Software Foundation, Inc. This work is licensed under a Creative Commons Attribution-No Derivative Works 3.0 license (or later version) 

 This is the phylogenic tree of mammals.  It shows evolutionary relationships throughout the selected mammals.  In general, organisms that share similar morphologies will have similar DNA sequences unless convergent evolution  occurs causing separate lineages of organisms to acquire similar adaptations.  According to the phylogenic tree,  Rattus norvegicus appears to more closely related to the rabbit than to the beaver.  The furthest away from being related to the rat is the duck-billed platypus.

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Copy right @ 2003, 2004 All rights reserved to Anne Hanson who earned a M.S. and Ph. D in animal behavior