Science of Water : Concepts and Applications

Water Biology 123
KEY TERMS
Key terms related to the discussion to follow and their basic defi nitions are listed below.
Algae Simple plants, many microscopic, containing chlorophyll. Freshwater algae are diverse
in shape, color, size, and habitat. They are the basic link in the conversion of inorganic
constituents in water into organic constituents.
Algal bloom Sudden spurts of algal growth, which can affect water quality adversely and indicate
potentially hazardous changes in local water chemistry.
Anaerobic Able to live and grow in the absence of free oxygen.
Autotrophic organisms Produce food from inorganic substances.
Bacteria Single cell, microscopic living organisms (single-celled microorganisms) that possess
rigid cell walls. They may be aerobic, anaerobic, or facultative; they can cause disease;
and some are important in pollution control.
Biogeochemical cycle The chemical interactions between the atmosphere, hydrosphere, and
biosphere.
Coliform organism Microorganisms found in the intestinal tract of humans and animals. Their
presence in water indicates fecal pollution and potentially adverse contamination by
pathogens.
Denitrifi cation The anaerobic biological reduction of nitrate to nitrogen gas.
Fungi Simple plants lacking in ability to produce energy through photosynthesis.
Heterotrophic organism Organisms that are dependent on organic matter for foods.
Prokaryotic cell The simple cell type, characterized by the lack of a nuclear membrane and the
absence of mitochondria.
Virus The smallest form of microorganisms capable of causing disease.
MICROORGANISMS (IN GENERAL)
The microorganisms of concern to water specialists are tiny organisms that make up a large and
diverse group of free-living forms; they exist either as single cells, cell bunches, or clusters.
Found in abundance almost anywhere on Earth, the vast majority of microorganisms are not
harmful. Many microorganisms, or microbes, occur as single cells (unicellular). Some are multicellular;
others, such as viruses, do not have a true cellular appearance.
Mostly, a single microbial cell exhibits the characteristic features common to other biological
systems, such as metabolism, reproduction, and growth.
CLASSIFICATION
For centuries, scientists classifi ed the forms of life visible to the naked eye as either animal or plant.
The Swedish naturalist Carolus Linnaeus organized much of the current knowledge about living
things in 1735.
The importance of organizing or classifying organisms cannot be overstated, for without a
classifi cation scheme, it would be diffi cult to establish a criteria for identifying organisms and to
arrange similar organisms into groups. Probably the most important reason for classifying organisms
is to make things less confusing (Wistreich and Lechtman, 1980).
Linnaeus was quite innovative in the classifi cation of organisms. One of his innovations is still
with us today: the binomial system of nomenclature. Under the binomial system, all organisms
are generally described by a two-word scientifi c name, the genus and species. Genus and species
are groups that are part of hierarchy of groups of increasing size, based on their taxonomy. This
hierarchy follows:
Kingdom
Phylum