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
Molecular Classification
13
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
Eukaryotic Origins
The nucleus and
endoplasmic reticulum
arose from infoldings of
prokaryotic cell
membrane
16
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
Fig. 29.5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Amoeboza
Opisthokonta
Animals
Choanoflagellates
Euglenozoa
Fungi
Diplomonads
Parabasalid
Chlorophytes
Land plants
Cercozoa
Foraminifera
Radiolara
Excavata
Amoebozoa
Archaeplastida
Rhodophyta
Brown algae
Diatoms
Stramenopila
Ciliates
Apicomplexans
Alveolata
Rhizaria
Charophytes
Chromalveolata
Oomycetes
Archaea
Dinoflagellates
Eubacteria
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.
Fig. 29.8
6 µm
a.
Stigma
Second flagellum
Reservoir
Contractile vacuole
Paramylon granule
Basal bodies
Mitochondrion
Pellicle
Nucleus
Chloroplast
Flagellum
b.
a: © Andrew Syred/Photo Researchers, Inc.
A ciliated protozoan
Too diverse for one kingdom: a diatom, a unicellular "alga"
Fig. 29.13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ptychodiscus
Noctiluca
Gonyaulax
Ceratium
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)
Fig. 29.27
Gametes
+
+Gametangia
+Gametophyte (n)
Zygote
n
2n
Germinating
zygote
Spores
Sporophyte (2n)
Sporangia
© 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
Kingdom Fungi
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)
Table 32.1
General Biology of the Fungi
Multicellular fungi consist of long, slender
filaments called hyphae
-Some hyphae
are continuous
-Others are
divided by
septa
33
General Biology of the Fungi
A mass of connected hyphae is called a mycelium
-It grows through and digests its substrate
34
Fungal mycelia
Fungal Parasites and Pathogens
Largest Organism?
Armillaria –a pathogenic fungus – 8 hectares
37
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
Zygomycetes
43
Lichens
• Mutualism between fungi and algae or
cyanobacteria
• Sensitive to pollution due to absorption
capabilitues
Fig. 32.15
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fruticose Lichen
a.
Foliose Lichen
b.
Crustose Lichen
c.
a: © Ken Wagner/Phototake; b: © Robert & Jean Pollock/Visuals Unlimited; c: © Robert Lee/Photo Researchers, Inc.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 32.16
Algal
cells
Fungal
hyphae
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. 32.17
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Arbuscular Mycorrhizae
Ectomycorrhizae
Root
5 µm
a.
50 µm
b.
a: © Eye of Science/Photo Researchers, Inc.; b: © Dr. Gerald Van Dyke/Visuals Unlimited