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In chapter 26 you learned the most
commonly used taxonomic scheme is as
follows:
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Domain
Kingdom
Phylum (Division)
Class
Order
Family
Genus
Species
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This new scheme represents a change from
the previous 5 or 6 kingdom scheme.
The old 5 kingdom scheme grouped all
prokaryotes together: i.e. eubacteria and
archaebacteria were grouped into the
Kingdom Monera.
The six kingdom scheme recognized that
archaebacteria were significantly different
from eubacteria and should be placed into
their own kingdom.
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However, neither of
these schemes
showed a phylogenic
relationship…i.e.
how did the
kingdoms evolve
from an ancient
ancestor.
The concept of 3
Domains was then
developed and a
phylogenic tree of
life was created.
This tree begins with
a common ancestor.
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The common ancestor was most likely a
small, unicellular prokaryote.
It would have had Nucleic Acid (DNA or RNA)
as genetic material to code for proteins
It would have had ribosomes to produce
proteins
It would have been surrounded by a
phospholipid bilayer
It would have used glycolysis as a means of
extracting energy from glucose
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The three domains now show that eubacteria
represent one of the branches descending
from the common ancestor.
The second branch divides into the
archaebacteria and eukaryotes
This illustrates that archaebacteria are
believed to be more closely related to
eukaryotes than to the other prokaryotes.
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A major goal of taxonomy is to organize taxa
on the basis of phylogeny (evolutionary
relationships)
Systematics = study of the evolutionary
relationships among organisms
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Eukaryotic Cells
◦ Long, linear DNA molecule packaged into
chromosomes by wrapping around histone proteins
◦ DNA is enclosed in the nucleus
◦ Specialized membrane-bound organelles isolate
metabolic activities
◦ Flagella and cilia, when present, are made of the
protein tubulin arranged in a 9 + 2 array.
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Prokaryotic Cells
◦ Short, circular DNA creating a single chromosome
◦ Many contain plasmids in addition to the major
chromosome
◦ No nucleus
◦ No organelles (some have various membranes that
serve similar functions)
◦ Flagella, when present, consist of the globular
protein flagellin
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Archaea (Archaebacteria) are prokaryotes that
differ from other prokaryotes and from
eukaryotes in the following manner:
◦ Cell walls only contain various polysaccharides, not
peptidoglycans (as in bacteria), cellulose (as in
plants) or chitin (as in fungi)
◦ The phospholipids of the plasma membranes differ
in their chemical structure from the phospholipids
of prokaryotes and eukaryotes
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Archaea are
similar to
eukaryotes
◦ DNA of both are
associated with
histones (Bacteria
DNA is not)
◦ Ribosome activity of
both is not inhibited
by antibiotics
(streptomycin and
chloramphenicol)
Bacteria is inhibited.
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Bacteria (Eubacteria):
differ from archaea and
eukaryotes by the
following
◦ Cell walls are made of
peptidoglycan (a polymer of
a monosaccharide with
amino acids)
◦ DNA is not associated with
histone proteins
◦ Ribosome activity inhibited
by streptomycin and
chloramphenicol
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Four Kingdoms: Protista, Fungi, Plantae,
Animalia
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Protists can be animallike, plant-like or funguslike
Protists can be unicellular
or multicellular
Determining evolutionary
relationships in this
kingdom is very difficult
Groupings are more
morphologically based.
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Photosynthetic protists
◦ Euglenoids: one to three
flagella, locate light for
photosynthesis with an
eyespot, can become
heterotrophic in the
absence of light.
◦ Dinoflagellates: two
flagella, spin through
water, many produce a
nerve toxin that is
poisonous to fish, shell fish
and humans: cause red
tides
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Diatoms: have shells
made of silica that fit
together like box lid:
many shapes
Phaeophyta (brown
algae) multicellular—
kelp
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Rhodophyta (red algae):
multicellular with red
accessory pigments
(phycobilins)
Chlorophyta (green
algae): unicellular,
colonial, or
multicellular: probably
the ancestor to plants.
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Heterotrophic
protists
◦ Rhizopoda (amoebas):
move with pseudopod
◦ Foraminifera (forams):
made of calcium
carbonate: amoeboid
protists
◦ Apicomplexans (animal
parasites): do not
move on their own:
must live within a host
(malaria parasite)
◦ Ciliates (paramecium):
move using cilia: most
complex: contain two
nuclei
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Either form filaments
or spore-bearing
bodies similar to the
fungi.
◦ Cellular Slime Molds:
go through different
life stages: spores
germinate into an
amoeba stage which
feeds on bacteria:
fungus stage in which
cells unite to form
fruiting bodies that
produces spores
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Plamodial Slime Molds: single spreading mass called
a plasmodium feeds on decaying vegetation grows
from diploid cells that arise from the joining of
haploid spores.
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Oomycota: water molds and downy mildews:
form hyphae (much like fungi): cell walls are
cellulose not chitin: parasitic or saprophytic
Watermold on a fish
Downy mildew on a leaf
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Fungi are either parasites or saprophytes
Absorb nutrients by the breakdown of
products by digestive enzymes.
Their bodies consist of long filaments known
as hyphae (mass of hyphae = mycelium)
Reproduce asexually by fragmentation,
budding or producing asexual spores.
Six groups are identified:
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Zygomycota: form
haploid zygospores that
grow into new hyphae:
ex: bread mold
Glomeromycota: exist in
a mutualistic relationship
with plant roots (
mycorrhizae): plant
provides carbs for the
fungus; fungus increases
the ability of the plant
roots to absorb nutrients.
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Ascomycota:
produce haploid
ascospores inside a
structure called an
ascus: Ex: Yeast,
truffles
Basidiomycota:
produce haploid
spores in a basidia
Ex: Mushrooms
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Deuteromycota:
imperfect fungi: no sexual
cycle has been
determined. Ex:
Penicillium
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Lichens: mutualistic
relationship between
algae and fungi. Algae
provides sugar
(photosynthesis); fungi
provides water and
improves growing
conditions.
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Multicellular, photosynthetic, eukaryotic
organisms with cell walls made of cellulose.
Dominant generation is usually diploid
Six major divisions:
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Bryophyta (mosses, liverworts, hornworts)
Lycophyta (club moss)
Sphenophyta (horsetails)
Pterophyta (ferns)
Coniferophyta (gymnosperms)
Anthophyta (angiosperms)
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Multicellular, heterotrophic,
eukaryotic organisms
Dominant generation is
diploid
Usually motile
Embryonic development
involves the formation of
tissue layers
Very diverse
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Porifera (sponges)
Cnidaria (jellyfish)
Platyhelminthes (flatworms)
Nematoda (roundworms)
Annelida (segmented worms)
Mollusca (mollusks: snails, clams, octopus )
Arthropoda (arthropods: crustaceans, insects)
Echinodermata (starfish)
Chordata (vertebrates)