5 Steps to a 5 AP Biology, 2014-2015 Edition

Taxonomy and Classification ❮ 155

Reactivity with Oxygen

A second way to classify moneran organisms is by their ability to react with oxygen: whether

theymustreact with oxygen to survive, whether they must be withoutoxygen to survive, or

if they can survive with or without oxygen. There are three classes of oxygen reactivity: oblig-

ate aerobes and obligate anaerobes at the two extremes of the spectrum, and facultative

anaerobes somewhere in between. Obligate aerobesrequire oxygen for respiration—they

must have oxygen to grow; obligate anaerobesmust avoid oxygen like the plague—oxygen

is a poison to them; facultative anaerobesare happy to use O 2 when available, but can sur-

vive without it.

Archaebacteria Versus Eubacteria

There are two major branches of prokaryotic evolution: Eubacteria and Archaebacteria.

Archaebacteriatend to live in extreme environments and are thought to resemble the first

cells of the earth. The major examples you should be familiar with include (1) extreme

halophiles—these are the “salt lovers” and live in environments with high salt concentra-

tions, (2) methanogens—bacteria that produce methane as a by-product, and (3) thermo

acidophiles—bacteria that love hot, acidic environments.

Eubacteriaare categorized according to their mode of acquiring nutrients, their mech-

anism of movement, and their shape, among other things. The following is a list of the

names of a few groups of bacteria that you should be familiar with for the AP exam:

1. Proteobacteria


2. Gram-positive bacteria


3. Cyanobacteria


4. Spirochetes


5. Chlamydias


6. Chemosynthetic bacteria


7. Nitrogen-fixing bacteria
   The three basic shapes of bacteria you might want to be familiar with include:


8. Rod-shaped bacteria:also known as bacilli(e.g.,Bacillus anthracis,the bug that causes
   anthrax).


9. Spiral-shaped bacteria:also known as spirilla(e.g.,Treponema pallidum,the bug that
   causes syphilis).


10. Sphere-shaped bacteria:also known as cocci(e.g.,Streptococcus,the fine bug that gives us
    strep throat).
    To summarize, the kingdom Monera can be subdivided according to the following
    characteristics:

Nutrition type? Autotroph versus heterotroph

Oxygen preference? Obligate aerobes versus obligate anaerobes versus

facultative anaerobes

Evolutionary branch? Archaebacteria versus Eubacteria

Endosymbiotic Theory

The endosymbiotic theorystates that eukaryotic cells originated from a symbiotic part-

nership of prokaryotic cells. This theory focuses on the origin of mitochondria and chloro-

plasts from aerobic heterotrophic and photosynthetic prokaryotes, respectively.

KEY IDEA

Bill (11th grade):
“Important con-
cept to know.”

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