ESS Topic 2: Ecosystems and Ecology

Ecology

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%