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Three Domains of Life
Protists
Three Domains of Life
Changes in Classification• The ‘old school’ method of classification included 5
Kingdoms (what I learned in school)– Monera– Protista– Fungi– Plantae– Animalia
• Today, advances in molecular technology expanded our understanding (and interpretation) of systematics
Modern Systematics• Three Domain classification of life • Numerous, virtually countless Kingdoms• Bacteria and Archaea are now 2 distinct
Domains (once included together in Kingdom Monera)
• Protista, Fungi, Plantae, and Animalia remain classified as distinct Kingdoms, although classification of the kingdom Protista has been met with complications
Prokaryotes
• Includes the kingdoms Archaea & Bacteria • Oldest, structurally-simplest, and most
abundant forms of life• Photosynthesis Bacterial and Eukaryotic
Diversity• Important decomposers and symbionts
Prokaryotes
• Unicellular• Typically 1μm or less (1000 μm = 1mm;
1000mm = 1 meter)• No membrane-bound nucleus; instead a
single circular chromosome made of DNA• Asexual reproduction by binary fission• Photosynthetic bacteria utilize oxygen or
chemical compounds, such as sulfur
Prokaryotic Cell Structure• Three basic forms:
– Bacillus – rod-shaped– Coccus - sphercal or ovoid-shaped – Spirillum – spiral or helical
Prokaryotic Cell Structure• Prokaryotes have a tough cell wall and other
external structures• Cell wall consists of peptidoglycan; a rigid
network of polysaccharide strands cross-linked by peptide side chains; unique to Bacteria
• Maintains the shape of the cell and protects it from swelling and rupturing
• Prokaryotes can have 1 or more flagella (much less complex than in Eukaryotes)
• Some Prokaryotes possess pilli, which helps fasten cell to host membrane
Domain Archaea• Once considered a subdivision of the Kingdom
Monera, now its own domain• Like all prokaryotes, Archaea are single-celled
microorganisms that lack a nucleus and membrane-bound organelles
• Best known for the “extremophiles” – Archaea which thrive in extremely harsh environments
Archea - Extremophiles• Thermophiles – thrive at
60-80°C (>176°F!)• Acidophiles – thrive at pH
at or below pH 3• Xerophiles – grow in
extremely dry conditions• Halophiles – require
extremely high concentrations of salt
http://www.dpchallenge.com/image.php?IMAGE_ID=448561
Dr. Anastasia’s lecture starts here
13
Molecular Classification
Bacteria and Archae differ fundamentally
• Cell Wall– Bacterial cell walls are made of peptidoglycan, Archae are not
• Gene expression– Archaea may have more than one RNA polymerase (Transcription:
reads DNA to make RNA), and these enzymes more closely resemble the eukaryotic RNA polymerases than they do the single bacterial RNA polymerase
16
Eukaryotic OriginsThe nucleus and
endoplasmic reticulum arose from infoldings of prokaryotic cell membrane
Endosymbiotic theory• Eukaryotic organelles
evolved from a consortium of symbiotic prokaryotes– mitochondria were
aerobic heterotrophic prokaryotes
– chloroplasts were photosynthetic prokaryotes
Kingdom Protista• Eukaryotic• Most are unicellular (there are some simple
multicellular ones)• Originally consisted of all unicellular eukaryotes• was paraphyletic• The 17 major protist phyla are grouped into six
major monophyletic groups
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cil
iate
s
Ap
ico
mp
lex
ans
ArchaeaEubacteria Chromalveolata Rhizaria Archaeplastida Excavata Amoeboza Opisthokonta
Par
aba
sal
id
Din
ofl
ag
ella
tes
Alveolata Stramenopila Rhodophyta Chlorophytes Diplomonads Euglenozoa Choanoflagellates
An
ima
ls
Fu
ng
i
Am
oeb
ozo
a
La
nd
pla
nts
Ch
aro
ph
yte
s
Ce
rco
zoa
Fo
ram
inif
era
Ra
dio
lara
Bro
wn
alg
ae
Dia
tom
s
Oo
myc
ete
s
Fig. 29.5
Paraphyletic – includes common
ancestor but not all descendents
Characteristics Used to Classify Protists
• Mode of locomotion• mode of nutrition• overall body form• pigments• & others…
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Second flagellumStigma
Contractile vacuole
Paramylon granule
Nucleus
ChloroplastFlagellum
Pellicle
MitochondrionBasal bodies
Reservoir
b.
a. 6 µm
Fig. 29.8
a: © Andrew Syred/Photo Researchers, Inc.
A ciliated protozoan
Too diverse for one kingdom: a diatom, a unicellular "alga"
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ptychodiscus
Noctiluca
Ceratium
Gonyaulax
Fig. 29.13
Too diverse for one kingdom: Australian bull kelp (Durvillea potatorum)
Fig. 29.24
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
+
Gametangia
Gametophyte (n)
Gametes
+Gametangia
+Gametophyte (n)
Spores
Sporangia
Sporophyte (2n)
Germinatingzygote
n
2n
Zygote
MEI
OSI
S
FERTILIZATION
Fig. 29.27
© Dr. Diane S. Littler
Too diverse for one kingdom: Amoeba proteus, a unicellular "protozoan"
Too diverse for one kingdom: a slime mold (Physarum polychalum)
Kingdom Fungi
• Eukaryotes, mostly multicellular, heterotrophic, have cell walls (chitin)
• decomposers, food, some cause disease• Acquire nutrients through absorption
Mycologists believe there may be as many as 1.5 million fungal species
Fungi are classified into 5 major phyla based on mode of reproduction-Chytrids (aquatic, flagellated, ancestral)-Zygomycetes (bread molds)-Glomeromycetes (mycorrhizae)-Ascomycetes (bread yeast, truffles)-Basidiomycetes (mushrooms)
Kingdom Fungi
Table 32.1
33
General Biology of the FungiMulticellular fungi consist of long, slender
filaments called hyphae
-Some hyphae are continuous
-Others are divided by septa
34
General Biology of the FungiA mass of connected hyphae is called a mycelium
-It grows through and digests its substrate
Fungal mycelia
37
Fungal Parasites and Pathogens
Largest Organism? Armillaria –a pathogenic fungus – 8 hectares
Fungi Reproduction• spores are produced either sexually or asexually• hyphae and spore nuclei are haploid
– except for a brief diploid stage that occurs during sexual reproduction
Figure 31.3 Generalized life cycle of fungi (Layer 1)
Figure 31.3 Generalized life cycle of fungi (Layer 2)
Figure 31.3 Generalized life cycle of fungi (Layer 3)
Figure 31.6 The common mold Rhizopus decomposing strawberries
43
Zygomycetes
Lichens
• Mutualism between fungi and algae or cyanobacteria
• Sensitive to pollution due to absorption capabilitues
Fig. 32.15Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. b. c.
Fruticose Lichen Crustose LichenFoliose Lichen
a: © Ken Wagner/Phototake; b: © Robert & Jean Pollock/Visuals Unlimited; c: © Robert Lee/Photo Researchers, Inc.
Fig. 32.16Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Algalcells
Fungalhyphae
40 μm © Ed Reschke
Mycorrhizae
• Mutualism between fungi and the roots of 90% of all vascular plants
• Increases absorption of phosphorous, zinc & other nutrients
Fig. 32.17Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. b.
Root
50 µm5 µm
Arbuscular Mycorrhizae Ectomycorrhizae
a: © Eye of Science/Photo Researchers, Inc.; b: © Dr. Gerald Van Dyke/Visuals Unlimited