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Copyright ©2000-06
P.D. Schreuders


Abiotic - Not involving or producing organisms.

Absorbers - Absorbers are bacteria and fungi that excrete enzymes into their environment.The digested molecules are then small enough to pass through the cellular membrane and be used.

Aerobic Bacteria - living, active, or occurring only in the presence of oxygen.

Algae - Photosynthetic protists dominated by single-cell species. Algae are the basis of nearly all aquatic food webs.

Alkalinity - A buffer that can prevent changes in pH despite an amount of a potential pH changing solution to the system.

Arthropoda - The phyllum to which Crustacea belong.

Astacida - The superfamily to which crayfish belong.

Astacoidea - The family of crayfish geographically isolated to the Northern Hemisphere, they are physiologically distinct from Parastacoidea.

Autotrophs - Any organism that converts energy from the physical environment into organically usable compounds.

BOD (Biochemical Oxygen Demand) - Measure of the quantity of oxygen used by microorganisms. High BOD levels mean the microorganisms are using up all of the oxygen in the environment and leaving less for other organisms.

Biogeochemical Cycling - The exchange between biologic, geologic, and chemical aspects of the environment.

Biogeographical Zones - Scientists divide the earth into biogeographical zones by the distribution of either animals (Faunal Zones) or plants (Floral Zones).

Biomass - The weight of all organisms in a certain trophic level. Usually measured in grams/square meter.

Biome - Biome refers to major divisions of Earth's land biota. Biomes are defined by structure and function.

Biosphere - The area of Earth where all life occurs.The term "biosphere" was coined by Edward Suess in 1875.

Biotic - Involving or producing organisms.

Brackish - Water containing a mix of freshwater and saltwater, with more saltwater than fresh but not as much as the sea.

Carnivores - Heterotrophs that feed on other animals.

Character - The physiologic trait a taxonomist uses to group organisms.

Chemoautotrophs - Organisms that use energy from inorganic chemical reactions to fuel their manufacture of organic matter.

Chitin - Semi-transparent horny substance that is the principle constituent of the exoskeleton of the crayfish.

Communities - A group of populations are called communities. Communities are hard to define, because organisms constantly move between communities.

Convergent Evolution - Convergent evolution results when unrelated species are acted on by the same selection pressure and adaptive traits tend to resemble traits in other species without a shared evolutionary lineage.

Crustacea - The subphyllum to which crayfish belong.

Cycles - The net inputs and outputs between parts of an ecosystem determine the availability of nutrients. Cycles are a mechanism of homeostasis in an ecosystem.

Cycling - In an ecosystem, chemical entities move between organisms, water, and the physical environment. These chemical entities can be nutrients, toxins, or energetic chemical compounds. Nutrient Cycling focuses on the cycling of chemical entities which are necessary for life.

Deionized Water - Ions have been removed from the water so they will not interfere in chemical reactions.

Detrital Food Web - A food web describing the flow of energy from photosynthetic organisms to detrivores. Most biologic energy moves through this food web.

Detrivores - Heterotrophs that feed on detritus, the little altered remains of living organisms.

Dietary Specialization - An qualitative scale of comparison based on an organism's feeding specificity. The scale ranges from generalist, less selective, to specialist, most selective.

Divergent Evolution - Selection pressure may also result in divergent evolution, where related lineages evolve different traits in response to different selection pressures.

DO (Dissolved Oxygen) Level - The amount of oxygen dissolved in a solution. Organisms living in your tank require DO to breathe or they would suffocate. A high amount of dissolved oxygen is beneficial to organisms living in the system and indicates a low level of pollution. Pollution will cause the DO level to drop and will make it hard for organisms to live in that system.

Ecology - concerns the interaction of life with the physical environment.

Ecosystem - Any group of organisms and the physical environment with which they interact. Ecosystems are characterized by their dominant biota.

Evolution - Evolution is the difference of traits that appear over time within a lineage of organisms. Through natural selection, some organisms with certain traits outlive others with different traits. The traits which are inheritable will increase in frequency in the next generation. Under constant pressure from natural selection, eventually some traits will be present in the population while others become absent.

Exoskeleton - Crayfish are covered by a thick but flexible exoskeleton which is calcified, and must be shed for growth. The exoskeleton is comprised of the epicuticle and procuticle.

Food Chains - Food chains describe the movement of energy and nutrients from plants to herbivores to carnivores. A food chain is different from a food web. Food chains have only the three links between plants, herbivores and carnivores.

Food Web, The - A conceptual model for mapping feeding interactions within an ecosystem. Ecologist Charles Elton developed the food web in the 1920's. Food webs are difficult to compile, and its data may be problematic, but food webs are still important. Food webs are not the only way to think of feeding interactions. Interactions with between species can be complicated, and determined more than just feeding.

Gastrolith - A stone or pebble ingested by an animal to assist in digestion. Crayfish store calcium in it and its used to help crayfish molt.

Gradualism - A theory regarding the time scale of evolution. Gradualism's central thesis is that evolutionary change accrues steadily over time.

Grazing Food Web - Food webs that describe the feeding relations of autotrophs that are grazed on by heterotrophs, which are then fed upon by higher carnivores.

Guilds - Robert Root proposed guilds to describe interactions between organisms. A guild focuses on a group of organisms which exploit a food source the same way. The large herbivores of the African savanna, wildebeest, zebra, and antelope, can all be a guild.

Herbivores - Hetertrophs that feed on plants.

Heterotroph - Any organism that cannot synthesize its own organic molecules. Heterotrophs must consume other organisms or organic waste.

Homeostasis - Homeostasis is the ability of a system to maintain internal equilibrium.

Ingesters - Ingesters have an internal space where digestion occurs. Ingesters also use enzymes to break down molecules into smaller substances for metabolic use.

Invertebrates - Animals are grouped by body plan. Invertebrates are animals that do not have a backbone.

Leguminous - Of or relating to legumes.

Lineage - An evolutionary line of descent.

Macroevolution - The large scale changes that occur over evolutionary time in a lineage.

Macrophytes - Plants.

Malacostraca - The higher crustaceans including crayfish. All malacostraca feature cephalization, a concentration of sensory organs in the head, and tagmatization, a body divided into functional units or tagma.

Microevolution - The changes in frequency of heritable traits in a population.

Natural Selection - Natural selection is the differential survivability of organisms expressing certain traits over other organisms. Evolution is said to occur through the process of natural selection, but they are not the same thing.

Nutrient Cycling - The cycling of chemical entities which are necessary for life.

Omnivores - Heterotrophs that feed on both plants and animals.

Organism - The individual plant, animal, bacteria, protozoan, or life form.

Oxidation - The loss of electrons by an atom, ion, or molecule.

Parastacoidea - The family of crayfish in the Southern Hemisphere.

pH - Measurement representing the Acidity/ Alkalinity of the solution.

Photoautotrophs - Autotrophs that utilize solar energy to synthesize organic compounds.

Photoperiod - Photoperiod is the length of the day, an indication of available sunlight.

Photosynthesis - The conversion of solar energy into biologic energy. Photosynthesis converts inorganic carbon, in the form of carbon dioxide (CO2), into organic matter and energy.

Phylogeny - Phylogeny, like taxonomy is based on physiologic similarities, but phylogeny also deals with evolutionary relatedness. Phylogeny uses common traits to interpolate the evolutionary past of a lineage of species.

Population - A group of organisms of the same species living within a defined area.

Primary Producers - Autotrophs are sometimes called primary producers. Primary productivity is the rate organic matter is produced.

Primary Productivity - Net primary production is the organic matter produced by plants after all metabolic needs have been met.

Producers - Autotrophs are sometimes called primary producers. Primary productivity is the rate organic matter is produced. Heterotrophs are sometimes called secondary producers. Secondary productivity is the rate of organic matter accumulation by heterotrophs.

Productivity - Productivity is the rate at which organic matter is produced or accumulated. Productivity is measured in weight (grams), or energy (Joules). These units are expressed per unit area, unit time.

Pseudogene - A gene with no function. These genes are thought to accumulate mutation at a higher rate than functional genes.

Racemes - A cluster of stalked flowers branching off of a single stem.

Rhizome - Subterranean plant that produces shoots above ground and extends its roots below ground.

Salinity - Consisting of or containing salt.

Secondary Producers - Heterotrophs are sometimes called secondary producers. Secondary productivity is the rate of organic matter accumulation by heterotrophs.

Secondary Productivity - Secondary production is determined by how much of the total energy took in goes toward new growth. A portion of the total energy ingested is lost as excreted waste. Energy must also be used in respiration. Secondary production is very hard to measure.

Serial homology - Where species develop features with the same evolutionary history across different lineages.

Sexual Selection - Sexual selection is a category of natural selection that occurs when individuals have different levels of reproductive success through competition.

Taxonomy - A science that groups organisms on the basis of physiologic similarities. Carolus Linnaeus, a Swedish naturalist working in the late 1700s, classified organisms into taxa (Kingdom, Phyllum, Class, Order, Family, Genus and Species) on the basis of physiologic similarities.

Time Scale of Evolution - Two theories dominate the debate on evolution's time scale: Gradualism is the theory that evolution occurs constantly, changes in trait frequency occur slowly over time. Saltation, or Punctuated Equilibrium, is the theory that evolutionary changes occur between long periods of equilibrium where traits don't change. Changes occur in relatively short intervals.

Turbid - Thick or opaque with sediment.

Water Hardness - Representative of the amount of calcium and magnesium salts dissolved in the water.

Vertebrates - Animals that feature a backbone.


Ppm - Part per million.

Ppt - Part per thousand.

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