Download UNIT 2 CLASSIFICATION READING: Chapter 14 Classification of

UNIT 2
CLASSIFICATION
READING:
Chapter 14
Chapter 19
Classification of Organisms
Introduction to the Kingdoms of Life
OBJECTIVES
At the end of this unit of study the student will be able to:
1.
Define taxonomy.
2.
Summarize the history and development of taxonomy.
3.
Describe the system of binomial nomenclature.
4.
List the seven basic levels of today's classification system.
5.
List and describe the evidence used by modern taxonomists to classify organisms.
6.
Define phylogeny and explain its importance.
7.
Define the role of biosystematics in inferring evolutionary relationships.
8.
Summarize the various systems of kingdoms that have been used in the past.
9.
Summarize the characteristics of the five kingdoms that are presently used.
ASSIGNMENTS:
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CLASSIFICATION
UNIT 2
I. TAXONOMY
A. Science of grouping organisms according to their presumed natural relationships.
1. Artificial - The way man views relationships between organisms
2. May change with new evidence.
B. History of Taxonomy
1. Aristotle - Greek Philosopher, 350 BC
a. Classified living things as either plants or animals.
b. Animals classified on where they lived.
1) Land dwellers
2) Water dwellers
3) Air dwellers
c. Plants classified on basis of stem differences
1) Herbs
2) Shrubs
3) Trees
2. Aristotle's method accepted until 18th century (1700s)
a. Newly discovered organisms didn't fit Aristotle's scheme
b. New systems developed
1) COMMON NAMES - everyday names given to organisms
a) Don't describe organisms accurately - jellyfish, silverfish are not fish.
b) Same name given to 2 different species - maple tree may be silver maple or red maple
c) Some organisms may have more than one common name - Sycamore, Buttonwood, or Plane
Tree – all the same
2) Early scientists used long Latin descriptions - too cumbersome
3. Carolus Linnaeus - Swedish Naturalist, 1707-1778
a. Developed system of grouping organisms into hierarchical categories.
1) SPECIES - structurally similar organisms
2) GENUS - similar species
3) FAMILY - similar genera
4) ORDER - similar families
5) CLASS - similar orders
6) PHYLUM - similar classes
7) KINGDOM - Linnaeus used either plant or animal
b. Chose to use only genus and species to name organism
1) System called BINOMIAL NOMENCLATURE - means "two names"
2) Binomial name of species also called SCIENTIFIC NAME
a) Scientific name usually describes organism or range of organism, or honors another scientist
or a friend.
(1) Trifolium agrarium - "three leaved"; "found in fields" - meadow clover
(2) Linnaea borealis - Linnaeus's favorite flower; "northern" - Twinflower
b) Name is always Latinized
c) Genus is always capitalized; species is always lower case.
d) Scientific name always italicized or underlined.
4. Levels of Classification
a. Seven Basic Levels - from broadest to narrowest.
1) Kingdom
2) Phylum
3) Class
4) Order
5) Family
6) Genus
7) Species
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b. Botanists use the term DIVISION instead of PHYLUM.
c. Taxonomists may use subgroups
1) SUBSPECIES - organisms that are morphologically different, geographically separated.
2) VARIETIES of Species - morphologically different, not geographically separated.
3) STRAIN - biochemically dissimilar group within a species; used with microorganisms.
d. DOMAIN
1) New more inclusive category above kingdom level
2) Developed because of molecular analyses
3) Three Domains
a) Bacteria - Kingdom Eubacteria
b) Archea - Kingdom Archaebacteria
c) Eukarya - Kingdoms Protista, Fungi, Plantae, and Animalia
II. Modern Taxonomy
A. Evidence used in classification
1. COMPARATIVE MORPHOLOGY
a. Morphological (physical) features used to determine categories.
b. Look at similarities of structures.
c. Identification often involves use of DICHOTOMOUS KEY
1) Set of written choices that leads to the name of an organism.
2) Dichotomous key - branches; make selections that become more and more specific.
d. Morphological evidence may not be sufficiently accurate.
2. Embryological Evidence
a. Usually used at level of larger classification categories - Phylum, class, etc.
b. Look at origin of certain body structures - common origin indicates related.
1) HOMOLOGOUS ORGANS - common origin, similar function - Bat's wing, human's arm,
whale's front flipper.
2) ANALOGOUS ORGANS - Similar function, different origin -Bird's wing Vs. insect's wing
3. Genetic similarities
a. Examine DNA sequences - closer related species have similarities
b. Study karyotype of 2 organism (picture of organism's chromosomes)
1) Chromosome count
2) Compare chromosome shapes
4. Biochemical Comparisons - related to genetic similarities
a. Compare amino acid sequences in common proteins - Hemoglobin.
b. Similarities indicate closer relationship
5. Physiological Studies - useful in Bacterial classification
a. Look at what chemicals bacteria can use as a food source
b. Look the same but classified into genera based on physiology
B. PHYLOGENY
1. Evolutionary history of a species.
2. Uses evidence of probable evolutionary relationships
3. PHYLOGENETIC TREE (Cladogram) - Visual model of inferred evolutionary relationships.
a. Species at branch tips represent most recently evolved organisms
b. Main branches and trunk represent organisms from which most recent organisms arose.
c. Branches in close proximity imply close evolutionary relationship.
C. BIOSYSTEMATICS
1. Study of reproductive compatibility and gene flow.
2. Use reproductive compatibility to infer evolutionary relationship.
3. Study SPECIATION - evolution of one species into two new species.
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III. Classification Systems - Kingdoms
A. Many systems have been and continue to be used.
1. Two Kingdoms
a. Plants
b. Animals
2. Three Kingdoms
a. Plants
c. Protists
b. Animals
3. Four Kingdoms
a. Plants - includes fungi
c. Protists
b. Animals
d. Monera
4. Five Kingdoms - system still used by some.
a. Plants
c. Protists
e. Fungi
b. Animals
d. Monera
5. Six Kingdoms - Presently in use
a. Plants
c. Protists
e. Eubacteria
b. Animals
d. Fungi
f. Archaebacteria
B. Criteria used to define kingdoms
1. Cell structure
4. Nutritional requirements
2. Cell Type
5. Developmental/reproductive patterns
3. Number of cells
C. Characteristics of the Kingdoms
1. Archaebacteria - Methanogens, Halophiles
a. Prokaryotic
b. Unicellular - Cell walls without peptidoglycan
c. Autotrophs or Heterotrophs
d. Live in extreme environments - volcanic hot springs, brine pools, black, anaerobic, organic
muds
2. Eubacteria - Bacteria and Blue-green Bacteria
a. Prokaryotic - lack nucleus and membrane bound organelles
b. Unicellular - Cell walls with peptidoglycan
c. Some heterotrophic, others autotrophic
d. Live in aquatic and terrestrial habitats
e. Most reproduce asexually - some species exchange genetic material
f. 5,000 species
3. Protista - Protists - Protozoa and Algae
a. Eukaryotic - have true nucleus and membrane bound organelles
b. Lack specialized tissue systems
c. May be unicellular or multicellular
d. Live in aquatic or moist habitats
e. Obtain food by ingestion, absorption, or photosynthesis - heterotrophs and autotrophs.
f. Reproduce sexually and asexually
g. 50,000 species
4. Fungi - Mushrooms, molds, yeasts, rusts
a. Eukaryotic
b. Heterotrophic
c. Some unicellular; most are multicellular
d. Most are terrestrial; a few are aquatic.
e. Reproduce sexually and asexually
f. 100,000 species
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5. Plantae - Plants - Mosses, ferns, conifers, flowering plants
a. Eukaryotic
b. Autotrophic
c. Multicellular
d. Most species are terrestrial, some aquatic
e. Reproduce sexually and asexually
f. Usually remain in one place.
g. 350,000 species
6. Animalia - Animals - sponges, worms, mollusks, vertebrates
a. Eukaryotic
b. Heterotrophic - obtain food by ingestion
c. Multicellular
d. Both aquatic and terrestrial
e. Most reproduce sexually; a few asexually
f. Most move about; some species stationary
g. Millions of species - largest kingdom
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