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photo at top:  Lower Little Cahaba River, taken by website's authors.

Below are terms used frequently in this website that are relevant to understanding and teaching river ecology.


Biodiversity:  diversity of all of the different plant and animal species in an environment.

Carnivore: an animal that eats other animals.

Collectors:  invertebrates that collect and consume very small particles of dead organic debris to obtain their energy. 

Community:  the collection of different species that are found in a specified area.

Crevice Spawner: an animal that uses crevices to deposit eggs.

Dissolved oxygenthe oxygen that is dissolved in water.  It is needed by any aquatic animals that do not breathe air.  Often referred to as “DO”.  DO levels tend to decline as water quality declines.

Ecology:  the study of interrelationships of living things to one another and to their environment.

Ecosystem: a system where populations of species group together in communities and interact with each other and the environment.

Endangered: animals, birds, fish, plants or other living organisms threatened with extinction by human caused or other natural changes in their

Endemic:  a species with a highly localized or restricted geographic distribution.

Energy:  the capacity to do work.  For many living organisms energy comes from eating other organisms. For plants, energy is derived from sunlight via photosynthesis.

Environment: all things that surround an organism.

Erosion: the wearing away of land surface by wind or water, intensified by land-clearing practices related to farming, residential or industrial
development, road building, or logging.

Eutrophication: when a body of water is choked by abundant plant life due to higher levels of nutritive compounds such as nitrogen and
phosphorus. Human activities can accelerate the process.

Extinct species:  species for which there are no more living individuals.  ‘Local extinction’ refers to when a species has disappeared from a specific area, usually at the scale of an entire ecosystem. 

Food web: complex interaction of food chains in a biological community.

Grazers:  organisms that eat living plants to obtain their energy.  Many aquatic snails, for example, are grazers that eat lots of algae.

Habitat: the place where a plant or animal lives; the food, water, shelter, and space an organism needs to survive.

Herbivore: an animal that eats plants.

Imperiled species:  species that are at risk of extinction.  For example, this would include  any species listed as threatened or endangered by the Endangered Species Act.

Impermeable: an area which is resistant to the absorption of water.

Invertebrate:  any animal without a backbone.

Larvae: the newly hatched, wingless, often wormlike form of many insects before metamorphosis.

Macroinvertabrate: an animal without a spine that can be seen without the aid of a microscope.

Omnivore: an animal that eats a broad range of foods (plants and animals).

Oxygen:  an element essential to life.  While we humans extract oxygen from the air via our lungs, many aquatic organisms aquire oxygen dissolved in the water.

Phytoplankton:  microscopic plants that live in water and harness sunlight to obtain their energy.

Population:  a group of individuals that belong to the same species. 

Predators:  any animal that eats other animals.

Rare species: species that are uncommon an/or hard to find

Sediment:  any debris that is deposited by a natural process. When discussing streams and rivers we use this term to describe non-living debris such as silt, sand, gravel, cobble, boulders, and any other material found in the streambed.

Shredders:  invertebrates that consume large pieces of dead organic debris (e.g., leaves, sticks) to obtain their energy.  They digest some of the organic material, but they also digest the bacteria and fungi that are decomposing that debris.

Silt: sedimentary materials composed of fine or intermediate - sized mineral particles.

Spawning:  a mode of external fertilization used by some animals where females and males release egg and sperm, respectively, into the water during reproduction. 

Species:  a group of organisms that have the capacity to successfully reproduce with one another.  Memebers of a species usually share many behavioral and morphological traits.

Storm water:  rainwater that flows off roads, buildings, yards, and any other impervious surfaces into a drainage system within a developed area.  This drainage system is often below our streets.  Stormwater is usually full of debri, trash, and pollutants, and usually flows into nearby streams, rivers, or other bodies of water.

Substrate: mineral or organic material that forms the bed of a stream.

Terrestrial:  dwelling on the land.

Threatened:  Any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion
of its range.

Vertebrate:  any animal with a backbone.

Wastewater:  water that has been processed by a stormwater or sewage treatment plant and is then discharged into the environment.   This water is usually free of most bacteria or other pathogens, but has high levels of nutrients and contaminants that are not removed by the treatment process.

Watershed: the area from which water flows onto a particular stream system.

Zooplankton: microscopic animals that live in water and eat microscopic plants

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