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32.1 Biologists name organisms in a systematic way.
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• Biologists give every species
a two-part (binomial) name that consists of the name of its genus plus
a distinctive specific epithet.
•In the hierarchical system of classification used in biology,
genera are grouped into families, families into orders, orders into classes,
classes into phyla, and phyla into kingdoms.
• There are perhaps 10 million species of plants, animals,
fungi, and eukaryotic microorganisms, but only about 1.5 million of them
have been assigned names. About 15% of the total number of species are
marine; the remainder are mostly terrestrial.
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1. What was
the polynomial system? Why didn't this system become the standard for
naming particular species?
2. From the most specific to the most general, what are the names
of the groups in the hierarchical taxonomic system? Which two are given
special consideration in the way in which they are printed? What are these
distinctions?
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32.2 Scientists construct
phylogenies to understand the evolutionary relationships among organisms.
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•Taxonomists
may use different approaches to classify organisms.
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Cladistic systems of classification arrange organisms according to evolutionary
relatedness based on the presence of shared, derived traits.
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Traditional taxonomy classifies organisms based on large amounts of information,
giving due weight to the evolutionary significance of certain characters.
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3. What types
of features are emphasized in a cladistic classification system? What
is the resulting relationship of organisms that are classified in this
manner?
4. What does it mean when characters are weighted?
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32.3 All living organisms
are grouped into one of a few major categories.
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A fundamental division among organisms is between prokaryotes, which lack
a true nucleus, and eukaryotes, which have a true nucleus and several
membrane-bound organelles.
• Prokaryotes, or bacteria, are assigned to two quite different
kingdoms, Archaebacteria and Eubacteria.
• The eukaryotic kingdoms are more closely related than are
the two kingdoms of prokaryotes. Many distinctive evolutionary lines of
unicellular eukaryotes exist, most are in the Protista kingdom.
• Three of the major evolutionary lines of eukaryotic organisms
that consist principally or entirely of multicellular organisms are recognized
as separate kingdoms: Plantae, Animalia, and Fungi.
•True multicellularity and sexuality are found only among
eukaryotes. Multicellularity confers the advantages of functional specialization.
Sexuality permits genetic variation among descendants.
• Viruses are not organisms and are not included in the classification
of organisms. They are self-replicating portions of the genomes of organisms.
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5. Is there
a greater fundamental difference between plants and animals or between
prokaryotes and eukaryotes? Explain.
6. From which of the four eukaryotic kingdoms have the other three
evolved?
7. What is the apparent origin of the organelles found in almost
all eukaryotes?
8. What defines if a collection of cells is truly multicellular?
Did multicellularity arise once or many times in the evolutionary process?
What advantages do multicellular organisms have over unicellular ones?
9. What are the three major types of life cycles in eukaryotes?
Describe the major events of each.
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