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KEY CONCEPT
Bacteria and Archaea are both single-celled
prokaryotes.
Prokaryotes are widespread on Earth.
• Prokaryotes can be grouped by their need for oxygen.
– obligate anaerobes
are poisoned by
oxygen
– obligate aerobes
need oxygen
– facultative aerobes
can live with or
without oxygen
• Domain Bacteria includes prokaryotes in the kingdom
Eubacteria.
– one of largest groups
on Earth
– classified by
1) shape
2) need for oxygen
3) diseases caused
Bacteria and archaea are structurally similar but have
different molecular characteristics.
• Bacteria commonly come in three forms.
– rod-shaped, called bacilli
– spiral, called spirilla or spirochetes
– spherical, called cocci
Lactobacilli: rod-shaped
Spirochaeta: spiral
Enterococci: spherical
• Archaea have many shapes.
• Bacteria and archaea have similar structures.
– plasmid
– flagellum
pili
plasma
– pili
membrance
chromosome
cell wall
plasmid
This diagram shows the typical structure
of a prokaryote. Archaea and bacteria
look very similar, although they have
important molecular differences.
flagellum
• Bacteria have molecular differences.
– The amount of peptidoglycan within the cell wall can
differ between bacteria
GRAM NEGATIVE
GRAM POSITIVE
– Archaea have different lipids entirely
Domain Archaea includes prokaryotes in the kingdom
Archaea.
• cell walls chemically
different from bacteria
– do not contain muramic
acid
– membrane lipids contain
branched carbon chains
• differences discovered by
studying RNA
• known for living in
extreme environments
KEY CONCEPT
http://www.funsci.com/fun3_en/protists/exhibition.
htm#green
Kingdom Protista is the most diverse of all the
kingdoms.
Protists can be animal-like, plantlike, or funguslike.
• Protists are eukaryotes that are not animals, plants, or
fungi.
• Animal-like protists consume other organisms.
– heterotrophs
– single-celled
• Plantlike protists are photosynthetic.
– single-celled, colonial, or multicellular
– no roots, stems, or leaves
• Funguslike protists decompose dead organisms.
– heterotrophs
– can move, whereas fungi cannot
Protists are difficult to classify.
• Protist classification will likely change.
– Some protists are not closely related.
– Molecular evidence supports reclassification.