Ecology
The study of interactions among and between organisms in their abiotic environment.
Abiotic Factors
The non-living, physical factors that influence the organisms and ecosystem — such as temperature, sunlight, pH, salinity, and precipitation.
Biotic Factors
The interactions between the organisms—such as predation, herbivory, parasitism, mutualism, disease, and competition.
Species
A group of organisms that share common characteristics and that interbreed to produce fertile offspring
Habitat
A habitat is the environment in which a species normally lives
Niche
A niche describes the particular set of abiotic and biotic conditions and resources to which an organism or population responds
Fundamental niche
Describes the full range of conditions and resources in which a species could survive and reproduce
Realized niche
Describes the actual conditions and resources in which a species exists due to biotic interactions
Resource Partitioning
The fundamental niches of two species overlap and through competition develop a narrower realized niche
Mutualism
Symbiotic relationship in which both partners benefit
Commensalism
A symbiotic relationship in which one organism benefits and the other one is neither harmed nor helped
Parasitism
Symbiotic relationship in which one species is benefited and the other is adversely affected
Predation
The consumption of one species (the prey) by another (the predator).​
Herbivory
The consumption of a plant species by an animal
Competition
This is the interaction between organisms that are trying to attain the same resources. This might be food but it could also be for mates, territory, nesting sites, etc.
Decomposer
Feeds on dead and decaying material, thus recycling the nutrients.
J-Shaped Curve
A population growth curve showing exponential growth with no carrying capacity reached.
S-Shaped Curve
A population growth curve showing exponential growth followed by slowed growth until carrying capacity is reached.
Carrying Capacity
The maximum population size that a given area can support sustainably.
Limiting Factors
Biotic or abiotic factors which lead to a limit in the population growth.
Density-dependent Limiting Factors
Limiting factors related to how densely packed a population is, e.g. competition
Density-independent Limiting Factors
Limiting factors unrelated to population density such as natural disasters and weather change.
Symbiosis
individuals living on or in individuals of another species where one or both species use the others resources. Includes mutualism, commensalism and parasitism.
community
a group of populations living and interacting with each other in a common habitat
ecosystem
a community and the physical environment with which it interacts.
Respiration
the conversion of organic matter into carbon dioxide and water in all living organisms, releasing energy.
Aerobic
using oxygen
anaerobic
without oxygen (e.g. water logged soil)
primary producers
in most ecosystems convert light energy into chemical energy in the process of photosynthesis
photosynthesis
the conversion of water and carbon dioxide in chloroplasts, using light energy, to organic matter
trophic level
the position that an organism occupies in a food chain, or the position of a group of organisms in a community that occupy the same position in
food chains.
Producers (autotrophs)
are typically plants or algae that produce their own food using photosynthesis and form the first trophic level in a food chain.
Chemosynthetic organisms
produce their own food without sunlight using the energy stored in chemical bonds, e.g. denitrifying bacteria
Ecological pyramids
include pyramids of numbers, biomass and productivity and are quantitative models that are usually measured for a given area and time
Bioaccumulation
the build-up of persistent or non-biodegradable pollutants within an organism or trophic level because they cannot be broken down
Biomagnification
the increase in concentration of persistent or non-biodegradable pollutants along a food chain.
Pyramids of numbers
graphically display the numbers of organisms at each trophic level in a food chain
Pyramid of biomass
represents the standing stock or storage of each trophic level, measured in units such as grams of biomass per square metre (g m-2) or Joules per square metre (J m-2) (units of biomass or energy).
Pyramid of productivity
flow of energy through a trophic level,
indicating the rate at which that stock/storage is being generated
Insolation
solar radiation
Productivity
the conversion of energy into biomass for a given period of time
Net Primary Productivity (NPP)
Gross primary productivity minus respiration losses (GPP - R)
Net secondary productivity (NSP)
calculated by subtracting respiratory losses (R) from GSP (NSP = GSP - R).
Gross secondary productivity (GSP) = Assimilation
Gross secondary productivity is the total energy or biomass assimilated by consumers and is calculated by subtracting the mass of fecal losses from the mass of food consumed (Food eaten - fecal loss)
Maximum sustainable yield
equivalent to the net primary or net secondary productivity of a system
Carbon sinks
stores in a system containing a lot of carbon, e.g. a forest or a peat bog
Flows in carbon cycle
consumption (feeding), death and decomposition, photosynthesis, respiration, dissolving and fossilization
Flows in nitrogen cycle
nitrogen fixation by bacteria and lightning, absorption, assimilation, consumption (feeding), excretion, death and decomposition, denitrification by bacteria
Human activities impacting carbon and nitrogen cycles
burning fossil fuels, deforestation, urbanisation, agriculture
nitrogen fixation
the conversion of nitrogen gas (N2) into compounds containing nitrates
denitrification
the conversion of nitrogen containing compounds into Nitrogen gas. This happens in water logged soil by anaerobic bacteria
Biome
a collection of ecosystems sharing similar climatic conditions
Succession
Succession is the process of change over time in an ecosystem involving pioneer, intermediate and climax communities.
Zonation
Zonation refers to changes in a community along an environmental gradient due to factors such as changes in altitude, latitude, tidal level or distance from shore (coverage by water).
insolation
the amount of solar radiation reaching a given area
precipitation
Rain, snow, sleet or hail - water that moves from a gaseous state, condenses and falls to the ground
tricellular model
the model which describes 3 large convection cells moving air from the equator towards the poles in each hemisphere of the earth that explains the distribution of precipitation and temperature that influence structure and relative productivity of different terrestrial biomes
terrestrial
relating to the earth i.e. ecosystems occurring on land
aquatic
relating to water i.e. ecosystems dominated by water
r-strategist
r-strategist species are those that produce large numbers of offspring so they can colonize new habitats quickly and make use of short-lived resources
K-strategist
K-strategist species tend to produce a small number of offspring, which increases their survival rate and enables them to survive in long-term climax communities.
climax community
There is no one climax community, but rather a set of alternative stable states for a given ecosystem. These depend on the climatic factors, the properties of the local soil and a range of random events that can occur over time.
Historically it is thought of as the community of organisms at the end point of succession but succession never really ends!
community respiration
The total respiration rate for all the populations within that system.
Productivity:Respiration Ratio
The ratio between how productive a system is and how much respiration is happening. As a system approaches its climax community, gross productivity equals respiration rates and so P:N approaches 1.
nutrient and energy pathways
The ways that nutrients/minerals and energy move through an ecosystem. These tend to become more complex as a system undergoes succession. Often represented by a food web.
alternative stable state
A stable state that is the result of a series of feedback loops and random events which give rise to a particular set of biotic and abiotic conditions. A particular system may be able to exist under several alternative stable states but will be the result of the random events and feedback.
stochastic
having a random probability distribution
climate
the average of the weather over a relatively longer period of time, usually about 30 years of data is required to give the climate of an area.
weather
the conditions is a given place at any one time. It is measured by the temperature, air pressure, precipitation (rain/snow etc.), wind speed, humidity.
Site description
A detailed description, giving the location and biotic and abiotic conditions of the ecosystem / community being studied.
Identification tools
keys, comparison to herbarium specimens or museum collections, genetic profiling, scientific expertise, apps for matching bird song etc, field guides
quantitative data
measuring, or measured by the quantity of something rather than its quality, e.g. the number of species
qualitative data
measured by the quality of something rather than its quantity, e.g. appearance of location
sampling strategy
the strategy designed to collect sufficient, appropriate data for a study that provides a valid representation of the system being studied
environmental gradient
a line joining location A to B which displays a change in certain abiotic conditions, e.g. going up a mountain leads to a change in altitude, temperature, air pressure and UV radiation
random sampling
an area is divided into a grid and coordinates are selected using a random number generator
systematic sampling
samples are taken at regular intervals, e.g. every 3m
quadrat
a square with a defined size that can be used to sample an area. The size can vary, for example, from 10cm2 for lichen sampling to 1km2 for tree sampling
transect
a straight line along which samples can be taken
Marine abiotic factors
salinity, pH, temperature, dissolved oxygen, wave action
Freshwater abiotic factors
turbidity, flow velocity, pH, temperature, dissolved oxygen
Terrestrial abiotic factors
temperature, light intensity, wind speed, particle size, slope, soil moisture, drainage, mineral content
Extrapolation
estimating or concluding something by assuming that existing trends will continue, e.g. extrapolate total biomass for an area from the samples taken
Estimating biomass
dry mass and extrapolate
estimating energy
controlled combustion and extrapolate
non-motile
organism that does not move
estimating abundance of non-motile organisms
use of quadrats, actual counts, measuring population density, percentage cover and percentage frequency
motile
organism capable of movement
estimating abundance of motile organisms
direct methods include actual counts (e.g. by aerial photography) and sampling; indirect methods include capture-mark-recapture with Lincoln Index
Lincoln Index
(n1 x n2) / nm where n1 is number caught in first sample, n2 is number caught in second sample and nm is number caught in second sample that were marked
Species richness
number of species in a community and is a useful comparative measure
Species diversity
is a function of the number of species and their relative abundance
Simpson Diversity Index (D)
N(N-1) / Sum of n(n-1) where N is the total number of organisms of all species found and n is the number of individuals of a particular species
percentage cover
an estimate of the area in a given frame size (quadrat) covered by the plant in question
percentage frequency
the number of occurences divided by the number of possible occurences; e.g. if a plant occures in 5 out of 100 squares in a grid quadrat, then the percentage frequency is 5%