Freshwater Ecology Final Exam Study Guide

Ecology

Scientific Study of interactions of organisms with their environments. Study of the factors controlling distribution and abundance of organisms.

Reductionist approach

seeking mechanisms, casual processes at levels of organization below that which we are trying to explain

Holistic approach

looking at higher levels of organization (the larger context) to detect external facotrs that affect the system under study, and to anticipate what consequences that systems’ dynamics will have at larger scales

Induction

inferring a generalization from a number of observations

Deduction

predicting a specific outcome from a more general hypothesis

Ecological experiment

manipulation of nature (biota or environmental factors) to investigate casual processes, using replication and controls

Control

treatment group in an experiment that is usually unmanipulated, so intended to represent the background condition. But sometimes Controls that impose “artifacts” (unwanted consequences of manipulations) are needed (for example, cage controls with one open wall that shade but don’t enclose cage contents).

Replicates

separate (independent) units of study that are treated identically by ecologists, in order to assess variability that arises from factors that weren’t manipulated

Models

simplifications of some more complex phenomenon used for understanding and prediction. Can be verbal, physical, or mathematical.

Model assumptions

conditions or relationships assumed as true when model was formulated

Model predictions

outcomes generated by the model under certain values of parameters (fitted or deduced constants) and variables (values of interest that change)

Parameters

a quantitative factor that helps define a system or sets the conditions of its operation—- often fitted or deduced constants used as coefficients or exponent in model equations

Variables

values of interest that change

Calibrating

fitting data to estimate model parameters

Validating

testing model predictions against new data

Density

mass/volume

Viscosity

force/area of a fluid that resists change in form of differential flows—thick, sticky consistency— water is 57x more viscous than air at room temperature

Inertia

resistance of a body to a change in its state of motion

Reynold number, Re

Ratio of intertial to viscous forces.

• Re = Fi/Fv predicts life in moving fluids (or moving through still fluids)

• if you are small or slow or both, viscosity matters more

• if you are large and fast, inertia matters more

Energy

ability to do work

Heat

energy arising from random motions of molecules in bodies or objects

Conduction

transfer of heat within a material

Convection

transport and mixing of heat and mass through a moving fluid (air or water)

Heat capacity

energy required to elevate temperature, amount of heat required to raise temperature of a unit volume of a material by one degree C

Thermocline

stratum (“thin layer”) of rapid temperature change, can seperate oxygenate from hypoxic habitat

Critical Zone

earth’s permeable near surface layer from the vegetation canopy down to the bottom of the weathered bedrock, the deepest zone from which water can move to support plants or replenish surface waters

Vadose Zone

unsaturated zone that holds underground water above the water table (mostly weathered bedrock but included soil too)

Water Table

level below which the ground is saturated with water.

• rises and falls with water supply and withdrawal

Drainage Area

landscape area upslope that imparts water to a lake, pond, or receiving channel.

Drainage divide

landscape ridges that demarcate areas draining into different receiving (“sink”) habitats

Gradient

slope (rise over run) of a channel or hillslope. ratio of drop in elevation per unit horizontal distance traveled downslope

Contour line

lien of equal elevation often depicted is rings or ellipses around hill on topography maps

Hyporheic

below the streambed

Phreatic

in ground water within saturated zone (below water table)

Phytotelmata

plant-held waters

Bogs

mossy wetlands fed primarily by precipitation. lack of flow exchange reduces oxygen, slow decomposition lowers pH, for other lentic habitats (e.g. fens, pocosins)

Adaptation

trait that confers a selective advantage of an organism relative to its absence in an ancestor

Autotroph

organism that fixes its own carbon, e.g. reducing CO2 to sugars during photosynthesis

Carotenoid pigments

dominant pigments in diatoms including carotene and xanthophyll, confer golden to reddish color

Critical Zone

the thin skin of the earth that stores and releases water to sustain vegetation or surface waters between precipitation events. The critical zone extends vertically from the top of the vegetation canopy down through soil and weathered bedrock, ending at the top of the unweathered bedrock where water can no longer move.

Denitrification

removal of bioavailable nitrates or nitrites by chemical reduction to nitrogen gas

Endosymbionts

an organism that lives within another organism. may be a parasite or a mutualistic partner

Epilithon

growing pebbles, stones and boulders.

Episammon

growing on sand

Epipelon

growing on unconsolidated substrates such as silt and mud

Epiphyton

growing on plants and filamentous algae

Eukaryote

organisms with an internal membrane-bound nucleus and other membrane-bound organelles

Exaptation

trait with an adaptive benefit, but one that was not acquired through natural selection (when an old trait acquires a new use in an environment in which it did not evolve)

Filament

a chain of connected cells

Frustule

a diatom cell wall made of silica dioxide (glass)

Heterotroph

organism that requires carbon fixed by some other organism (although this could be living carbon or detritus)

Host

a larger organism that provides a structural “home” (and sometimes other resources) for a smaller symbiotic “guest”

Host for epiphytic diatoms

green macroalga Cladophora

Oxidation

loss of electrons or an increase in oxidation state by a molecule, atom, or ion (“eating”)

Reduction

gain of electrons or a decrease in oxidatoin state by a molecule, atom, or ion (“breathing”)

Nitrogen fixation

reduction of N2 gas to bioavailable ammonia (NH3). Nitrogen-fixing prokaryotes do this with an ancient enzyme pathway that is poisoned by oxygen

Phenology

seasonal sequence of life cycle events for an organism or taxon

Plankton

algae that drift in the water column

Plastids

membrane-bound organelles in cells with pigments, like chloroplasts that contain green chlorophyll and carry out photosynthesis

Prokaryote

organisms that lack internal membrane-bound nuclei or other membrane-bound organelles

Raphe

a narrow slit in a diatom cell wall that enables their locomtion

Quantitative stable isotope probing (qSIP)

method of labeling a food substrate with heavy isotopes so that the prokaryotes that assimilate it can be identified taxonomically by density changes in their nucleic acids.

Valves

two overlapping havles of a diatom frustule. the larger valve is called the epitheca that fits over the small valve, the hypotheca (think of two halves of a petri dish)

Viruses (virions)

infective agent that typically consists of nucelic acid molecule (DNA or RNA) in a protein coat that can multilpy only within the living cells of a host

Virocells

the life history phase of the virion within the host cell

Bioindicator

any species or group whose function, population, or statuc can reveal the qualitative state of the environment (“canary in a coal mine”)

Shredders

invertebrates that break up coarse particulate organic matter (CPOM)

Collectors

invertebrates that filter or father fine particulate organic matter (FPOM)

Ametabolous

insects that undergo no metamorphosis (eggs to edults), immature adults look similar to mature adults

Hemimetabolous

insects that undergo partial metamorphosis (egg-nymph-adult), nymphs look like adults with wings

Holometabolous

insects that undergo partial metamorphosis (egg-larvae-pupae-adult). Larvae pupate into adult, big change from larvae to adult (via different instars)

Gas exchange

transporting O2 from the environment to the tissues, expellign Co2 from the tissues back tot he environment.

Hemoglobin

respiratory pigment that facilitates the capture of oxygen molecules

Thermoregulation

ability of an organism to keep its body temperature within certain boundaries, usually via behavioral or physiological adaptations

Ecosystem engineer

organism that directly or indirectly modifies the availability of resources to other species— by causing physical state changes in biotic or abiotic materials

Metapopulation

Set of populations potentially inked by dispersal

Riparian

Zone around a river that is strongly affected by it, for example by relatively frequent inundation, close proximity to the water table, or air moisture

Recruitment Box

zone defined in a graph of elevation and time in which riparian trees can recruit. the elevation band is controlled by the changing water table; the time window is defined by when the trees disperse ripe seeds

Allochthonous inputs

energy or organic matter “importe” from outside the aquatic ecosystem or study habitat (e.g. dead organic matter formed outside the ecoystem)

Autochthonous inputs

Energy or inorganic matter coming from within the habitat (e.g., benthic algae fixing carbob locally)

Macrophyte

aquatic vascular plant (emergent, submerged, or floatign)

Stress

any factor that reduces an organism’s performance. may be brief or prolonged.

Disturbance

discrete (pulsed) event that kills or removes organisms and frees space and resources

Synergistic interaction

effect of two stressors is greater than the sum of their separate (additive) effect

Antagonistic interaction

effect of two stressors is lower than the sum of their separative (additive effect)

Hyporheic zone

region beneath the stream bed, where there is mixing of shallow groundwater and surface water

Resilience

ability of an organism to overcome stress or disturbance by recolonizing from other habitats, via aerial aquatic or terrestrial dispersal

Resistance

ability of an organism to overcome stress or disturbance by dispersing ‘in time’, e.g. via a dormant stage

Hydroperiod

Seasonal pattern of water levels, generally applied to a lentic ecosystem and described by its characteristic length, timing, and predictability

Resurrection ecology

hatching dormant eggs from lake sediments to study animals from decades or centuries ago

Adaptation

trait that confers a selective advantage on an organism relative to its absence in an ancestor

Anhydrobiosis

ability to survive dehydration

Ecological trap

situation where environmental change leads organisms to mistakenly use poor-quality habitats (i.e. habitats where their fitness is lower than in other available habitats

Environmental autocorrelation

relationship between successive values of the same variable. can be measured across space or over time, and ranges from -1 to +1. Temporal autocorrelation is sometimes referred to as ‘memory’ of a variable, and positive values indicate that the variable changes slowly (i.e., successive values are similar). Similarly, positive spatial autocorrelation indicates that sites close to each other have similar values.