taxonomy Flashcards
taxonomy
Formal systematic organization of organisms into a coherent classification system
history of taxonomy
Linnaeus’ system based on similarities and difference
Tried to reveal god’s plan
steps in taxonomy
Define the unit of analysis = species
Use morphological similarities and dissimilarities
Select traits which reflect similarities resulting from evolutionary relationships
Classifying Organisms
Need to decide if similar traits are inherited from common ancestor or independent solutions to a particular problem
Differentiating between Homologs and Analogs
derived
features are unique to a particular level
primitive
features shared by a number of groups
homologous structures
Derived from a common ancestor
Feature present in that common ancestor
Example: forelimb of mammals
Predictions that last common ancestor mammals will have similar forelimb structure
analogs
Common form determined by common function
Physics of flight constant
Limited number of physically workable solutions
convergent evolution
Different populations through process of variation and selection end up with structural similar solutions
Only certain solutions to a particular problem are possible
cladistic system
Based exclusively on genealogy
evolutionary Systematics
Based on evolutionary history plus rates of evolutionary change
Grew out of concept of evolution which is gradual and continuous
evolutionary systematics primate groups
Prosimii
Anthropoids
cladistic primate groups
Strepsirhini
Haplorhini
evolutionary systematics ape groups
Hylobatidae - Gibbons
Pongidae - Orangutans, gorillas, chimpanzees
Hominidae - Humans
cladistics ape groups
Hylobatidae - Gibbons
Pongidae - Orangutans
Hominidae - Humans, gorillas, chimpanzees
determining homologies
Anatomical structures
Pattern of embryonic development
Proteins
DNA
anatomincal homology
The same basic structure
The same relationship to other body parts
Develop in a similar manner in the embryo
Embryonic Development
More distantly related vertebrates will have a shorter period during which they pass through similar embryonic stages
protein sequences
Molecular homology
Example: hemoglobin
The number of amino acid differences between the beta chain of humans and other species
dna
Proteins are expression of genes so why not compare the actual gene sequences
DNA-DNA hybridization
Chromosome painting
Phylogenetic Trees
Reconstructing evolutionary history of the molecule
Determine minimum number of nucleotide substitutions in the DNA
Computer program to search for the shortest paths linking the molecules together
Taxonomic Problems
Species is the only taxonomic category that exists in nature
Strict cladistic classification are too complex for convenience
Cladistic classification may often seem to violate common sense
Branches on phylogenetic tree are long and bunched so closely at base that it is difficult to determine relationships
As more data is available computer programs become overwhelmed
Changing rate of evolution
Gene transfer between species
Convergent evolution occurs at molecular level as well
