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Chapter 3 Humans among the Primates

Chapter 3 Humans among the Primates - Chapter 3 Humans...

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Chapter 3 – Humans among the Primates Names and Classifications - The Latin name for human beings, Homo sapiens , was coined by Swedish biologist Carl von Linne as part of his classification of plants and animals ( Systema Naturae ) - His binomial system used Latin because it was a convenient international language - Grouping similar plants and animals in classes, Linnaeus was using a kind of phenetic classification , a taxonomy based on physical similarities or differences between species or other taxa - Taxonomy is the classification of plants or animals according to their relationships and the ordering of these groups into hierarchies - Phylogenetic classification is a taxonomy that reflects evolutionary descent and is based on the pattern of primitive and derived traits - Taxa are groups of organisms at any level of a classification scheme - Cladisitic classification – equal weight is given to traits and requires sister groups to be similarly ranked - Primitive traits are characteristics inherited from an early ancestor and widely shared among descendents - Shared derived traits are characteristics inherited from a relatively recent ancestor and found among a few close taxa - Unique derived traits are characteristics that is a unique evolutionary adaptation of a species - A cladogram is a branching tree diagram displaying evolutionary relationships among organisms - A clade is a group of members of an evolutionary cluster plus their common ancestor - A clade with a single common ancestor is monophyletic (descended from a single common ancestral species) - Cladistic classifications try to identify groups of species or higher taxa according to traits that are similar by descent ( homologous traits ) which identifies evolutionary clusters, but is confused by the occurrence of homoplasies , or traits that result from independent adaptation to similar environments - Cladistic classifications do not express specific ancestor-descendent relationships (relationships can be observed as moving in reverse humans apes), sister groups are always given the same taxonomic rank, and treat individual traits equally - Traditional evolutionary classifications have traits given different weights, and sister groups are assigned to different taxonomic levels (however, the problem lies in the element of arbitrariness to classification) The Primates - St. George Mivart defined primates as placental mammals with these traits: claws or nails, collarbones, eye sockets encircled by bone, heterodont dentition (incisors, canines, molars), osterior lobe of a brain, thumbs or big toes (opposable), flat nail on big toe, caecum, pendulous penis, scrotal testes, two nipples - W.E. Le Gros Clark characterized primates by: retention of generalized limbs tipped with five grasping digits, replacement of claws by nails, retention of a tail, expansion and elaboration of the brain, emphasis on vision, deemphasis on olfaction, loss of teeth from
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