Lecture 5. Biology
A. Taxonomy and Diversity
The largest, overarching division in the classification (taxonomy) of life is the domain. Three domains
are recognized. Two of these, the Archaea and the Bacteria are prokaryotes (pre-nut), lacking internal
organelles (e.g. nucleus, mitochondria and chloroplasts). Archaea and Bacteria are similar in appearance
but differ markedly in genetic character. There are more than 10,000 named species of prokaryotes,
most in the domain Bacteria. The third domain is the Eukaryota (eukaryotes: true-nut) and possess
internal organelles.
[T] Dodson, Figure 3.6, p. 74
The domain Eukaryota is divided into four kingdoms: protists (algae and protozoa; 60,000 named
species), fungi (60,000+ named species), plants and animals. Kingdoms are further divided into phyla,
classes, orders, families, genera and species.
[T] Subdivisions of Domains, Wikipedia
B. Appearance and Anatomy
1) Prokaryotes
Prokaryotes (Archaea and Bacteria): are among the smallest of organisms with single cells ranging from
0.1 – 2.0 m. Three characteristic shapes are observed in prokaryotes: spherical (coccus), rod-shaped
(bacillus) and spiral (spirillum).
[T] Dodson, Figure 3.2, p. 68
Prokaryotes may grow as filaments (cyanobacteria) or colonies reaching millimeters to centimeters in
length.
[T] cyanobacteria
[T] bacterial colonies
2) Eurkaryotes
There is tremendous diversity in the Eukaryota, as the domain includes everything from algae to
sturgeon.
[T] spectrum of eukaryotes
(a) Protista – the kingdom includes one-celled organisms living either singly or in colonies. The
Protists include animal-like (protozoa) and plant-like (algae) organisms typically 1 – 50 m in length.
[T] protists
(b) Fungi – the kingdom includes spherical, single-cell forms (yeasts) and, more commonly,
filaments of single cells joined end-to-end to form hyphae.
(c) Plants – aquatic representatives of this kingdom are mostly large plants termed macrophytes
(this includes both macroalgae and flowering plants).
[T] macroalgae
[T] flowering plants
The flowering plants are typically classified by their growth habitat: submerged, floating or emergent.
[T] flowering plant growth habits
(d) Animals – again, a huge diversity
(1) rotifers (wheel animacules): multicellular animals made up of eukaryotic cells.
Ranging in size from 80 – 1500 m (0.08 – 1.5 mm), rotifers have cilia patches on their heads that give
the impression of rotation.
(2) branchiopods (gills on their appendages): small crustaceans (lobster and shrimp
relatives) ranging in size from 200 – 500 m (0.2 – 5.0 mm). Here, the subgroup of most importance to
us is the Cladocerans which includes Daphnia, Bosmina and the Great Lakes invader, Bythotrphes.
(3) copepods: small crustaceans (lobster and shrimp relatives) ranging in size from 1000
– 2000 m (1 – 2 mm). there are 10,000 species of copepods. Three orders illustrate characteristic
copepod body shapes.
[T] Dodson, Figure 4.14, p. 102
(4) malacostracans: this group includes crayfish and two orders (Amphipoda and
Mysidacea) that are particularly important in the Great Lakes; most prominently Diporeia and Mysis,
both about 1 mm in length.
(5) insecta: various life stages, e.g. larvae and pupae, inhabit lakes sediments. Among
these are included the bloodworm (Chironomus, chironomid) and the phantom midge (Chaoborus)
collected from Portage Lake.
(6) mollusca: this group includes the Class Bivalvia (clams and mussels; ~270 species)
and Class Gastropoda (snails; ~500 species), ranging in size on the order of mm to cm. Important
mollusks on the Great Lakes include the Family Sphaeriidae (freshwater snails) and the invasive Genus
Dreissena (zebra mussel, Dreissena polymorpha, and quagga mussel, Dreissena bugensis).
(7) fish: of both ecological and economic importance, the public relates water quality
and the health of the fish community.
[T] prominent Great Lakes and inland species; noting aliens
C. Feeding and Ecology