Chapter 18: Classification. 18-1 History of Taxonomy. 18-2 Modern Phylogenetic Taxonomy. 18-3 Two Modern Systems of Classification. 18-1 History of Taxonomy. I. Early Systems of Classification (Aristotle, Greece ~2,100 years ago).
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18-1 History of Taxonomy
18-2 Modern Phylogenetic Taxonomy
18-3 Two Modern Systems of Classification
I. Early Systems of Classification (Aristotle, Greece ~2,100 years ago)
(1) Linnaeus’s work was done many years before Darwin and Mendel. Explain why many of Linnaeus’s categories are still relevant in light of genetic and evolutionary relationships among organisms.
(2) Phylum: Arthropoda
(3) Class: Insecta
(4) Order: Mantodea
(5) Family: Mantidae
(6) Genus: Mantus
(7) Species: religiosa
(1) Genus (gets capitalized)
(2) Species Identifier (usually a descriptive word, lowercase)
Exs: Homo sapiens, Pisum sativum, Drosophila melanogaster
Ex: Terrapene carolina triungui is a SUBSPECIES of the common eastern box turtle, Terrapene carolina, and gets its NAME from having THREE (rather than four) toes on its HIND feet.
NOTE: By using morphology, Linnaeus focused on PHENOTYPES that were largely influenced by GENES and are STILL clues of common ANCESTRY.
I. Systematics (Systematic Taxonomy)
(2) Biologists believe that there are probably millions of undescribed and unclassified species on Earth. Why might so many species still be undescribed or unclassified today?
(a) Fossil Record
(d) Biochemical Comparison (amino acid, DNA, and chromosomes)
NOTE: Each cell in an embryo of a VERTEBRATE or ECHINODERM has the POTENTIAL to form an entire organism (TWINS), WHEREAS in invertebrates, if ANY cell is removed, it will DIE (pre-determined parts).
(3) Legs are an example of a shared derived character in vertebrates. Arthropods, such as lobsters and crickets, also have legs, but they are NOT accepted as a character shared with vertebrates. Why might this be?
(4) Why does the cladistic approach to classification suggest that the class Reptila (reptiles) is not a phylogenetic classification?
I. Six-Kingdom System (replacing old system of 5)
NOTE: Adapted to living in HARSH, hostile environments including sulfurous HOT Springs in Yellowstone National Park and SALT Lakes.
NOTE: Due do exponential growth AND a very short generation time, bacteria have a RAPID evolutionary RATE which may support their RESISTANCE to environmental change.
NOTE: Most unicellular AND aquatic, however can be plant-like, animal-like, or fungus-like protists.
NOTE: Fungi species secrete ENZYMES to break down organic materials into nutrients rather than ingesting them. (i.e., EXTRA-cellular digestion)
NOTE: Since ALL organisms (even archaebacteria) have ribosomes, the rRNA is used to study the PHYLOGENY between ANY two SPECIES.
(5) In the five-kingdom system, which is still used by some scientists, all species of bacteria are grouped into Kingdom Monera. Why might there have been only one bacterial kingdom in the past?
(1) Linnaeus based his system on morphological traits of an organism. Morphological traits are heavily influenced by genes, which are clues to common ancestry.
(2) Members of the class Reptilia appear to have evolved from several different ancestral lines. Reptiles consist of several groups that arose in parallel.
(3) Answers will vary, but students might suggest that because bacteria are small and fairly simple, they have few characters on which to base taxonomic decisions. Alternatively, they might suggest that differences between eubacteria and archaebacteria are mainly molecular and the technology for identifying such differences has only recently been developed.
(4) Many of the unclassified species may be few in number or may be located in remote habitats.
(5) Arthropod legs are structurally very different from the legs of vertebrates. Arthropod legs are covered by an exoskeleton and do not have an internal skeleton of bone.
Assessing Prior Knowledge