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

Hierarchy = organizational levels

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Each level is nested within the one above

Broad or less specific

More specific

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

ArchaeaMore 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