Phylogeny and Systematics
• What is meant by
phylogeny?
• Evolutionary history of a
species…
– Based on common ancestry
– Supported by shared
characteristics and genetics
– Documented by fossils and
genetics
Systematics?
= study of the organismal
diversity of life
How do we make sense of
all this diversity?
Organize it….
Taxonomy & classification
Diversity of Life
Each level is nested
Hierarchy = organizational within the one above
levels
Domain
Broad or less specific
Kingdom
Phylum
Class
Order
Family
Genus
More specific
Species
Closely related species belong to the same genus, similar genera are included in a family, etc…
Species that share the same structures, behaviors, etc, can interbreed and produce fertile offspring.
• Grouped by shared
characters (Evolutionary
relationships)
– Embryology
– Reproduction strategies
– Symmetry (body plan)
– Morphology
– Feeding mode
– Etc…
5 Kingdoms
3 domains, many kingdoms
Prokaryotic cell
Eukaryotic cell
Prokaryotes
• Single cell
• Very small
• Cell wall
• Lacks nucleus
• Lacks membrane
bound organelles
• Binary fission
• Domains: Bacteria and
Archaea
More structural & functional characteristics in (Ch.27)
How can we organize/compare Prokaryotes?
• Morphology
• Biochemistry
• Modes of nutrition
– Heterotrophic (hetero = other, trophic = food or feeding)
• Must consume organic molecules
– Autotrophic (self feeding)
• Photoautrophic can photosynthesize; get energy from sun
• Chemoautotrophic obtain energy from inorganic molecules
• Toxicity of Oxygen
– obligate aerobes, obligate anaerobes, facultative anaerobes
• Genetic Analysis
Bacilli
• Rod shaped
– Example: E. coli
• Usually solitary
• Sometimes chains
– streptobacilli
Cocci
• Spherical
– Clumps or clusters (like
grapes)
• E.g. Staphylococcus aureus
– Streptococci – chains of
spheres
– Diplococci – pairs of
spheres
• E.g. Neisseria gonnorheae
Streptococcus 1
Streptococcus 2
Diplococcus 1
Diplococcus 2
Spiral prokaryotes
• Spirilla – spiral shaped
– With external flagella
– Variable lengths
• Spirochaetes
– Internal flagella
– Corkscrew-like
• Boring action
• E.g. Treponema pallidum (Syphilis)
Biochemistry & cell surface structures
• Gram stain
– Counter stains to
differentiate between cell
wall characteristics
– Gram-positive
– Gram-negative
• Adaptations to
environmental variations
• salinity, temperature, pH,
O2 levels
Gram positive bact
• Thick layer of
peptidoglycans
• Retains crystal violet
– Doesn’t wash out
– Masks red safranin
• Stains dark purple or
blue-black
Gram negative bact
• Thin sandwiched layer
of peptidoglycans
• Rinses away crystal
violet
• Stains pink or red
Clades of bacteria
• Fig 27.18 (27.13 in 7th ed.)
• Proteobacteria
• Cyanobacteria
• Spirochaetes
• Gram positive bacteria
Proteobacteria
• Includes Gram negative
bacteria
– E. coli
• common intestinal flora
– Enterobacter aerogenes
• Pathogenic; causes UTI
– Serratia
• Facultative anaerobe
• Characteristically red
cultures
Proteobacteria: Myxobacteria
• Subgroup of
Proteobacteria
– Slime-secreting
decomposers
– Elaborate colonies
• Thrive collectively, yet
have the capacity to live
individually at some
point in their life cycle
Cyanobacteria
• “blue-green algae”
• Photoautotrophic
• Typically colonial
Oscillatoria (Cyanobacteria) 1
Oscillatoria 2
Anabaena (Cyanobacteria) 1
• Vegetative cell
– Primary metabolic function
(photosynthesis)
• Heterocyst
– Nitrogen fixation
• Akinete
– Dormant spore forming cell
Anabaena 2
Anaebena 3
Nostoc (Cyanobacteria) 1
Nostoc 2
Gleocapsa (Cyanobacteria) 1
Gleocapsa 2
Spirochaetes
• Long spiral
• Flagellated cell wall
• Decomposers &
pathogens
Gram positive bacteria
• Gram stains – purple
– Thick cell wall
• Includes:
– Micrococcus
• Common soil bacterium
• M. luteus cultures have
a yellow
– Bacillus
• B. subtilis are relatively
large rods; common
“lab organism”
• Obligate aerobes or
facultative anaerobes
Archaea family tree
Archaea -- “Extremophiles”
Tolerant to extreme environments
– Extreme thermophiles
• High and low temperature
• Commonly acidophilic
• E.g. hot sulfer springs, deep
sea vents
– Extreme halophiles
• High salt concentration
• Often contains carotenoids
• E.g. Salton Sea
– Methanogens
• Anaerobic environments
– Release methane
– E.g. animal guts