IB ESS Topic 2 - Ecosystems and Ecology

species

a group of organisms sharing common characteristics that interbreed and produce fertile offspring

population

a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding

habitat

the environment in which a species normally lives

abiotic factors

non-living, physical factors that influence the organisms and ecosystem, e.g. temperature, sunlight, pH, salinity, pollutants.

biotic factors

the living components of an ecosystem - organisms, their interactions or their waste - that directly or indirectly affect another organism

niche

the particular set of abiotic and biotic conditions and resources to which an organism or population responds.

fundamental niche

the full range of conditions and resources in which a species could survive and reproduce

realised niche

the actual conditions and resources in which a species exists due to biotic interactions.

limiting factors

factors which slow down growth of a population as it reaches its carrying capacity

carrying capacity

the maximum number of a species or 'load' that can be sustainably supported by a given area

population dynamics

the study of the factors that cause changes to population sizes

competition

when two or more individual organisms try to exploit a resource that is in limited supply

intraspecific competition

competition between members of the same species

interspecific competition

competition between individuals of different species

competitive exclusion

when interspecific competition results in one species being driven out by the other

predation

when one animal eats another animal

herbivory

when an animal eats a plant

parasitism

A symbiotic relationship where one organism (the parasite) lives in or on another (the host) feeding on or from it. One suffers, the other is harmed.

mutualism

a symbiotic relationship where both species benefit.

S and J population curves

generalised responses of populations to a particular set of conditions (biotic and abiotic factors)

community

a group of populations living and interacting with each other in a common habitat

ecosystem

a community and the physical environment it interacts with.

respiration

the conversion of organic matter into carbon dioxide and water in all living organisms, releasing energy.

photosynthesis

the process by which green plants make their own food from water and carbon dioxide using energy from sunlight

food chain

the flow of energy from one organism to the next. It shows the feeding relationships between species in an ecosystem

trophic level

the position that an organism occupies in a food chain, or in a group of organisms in a community that occupy the same position in food chains

compensation point

when all carbon dioxide that plants produce in respiration is used up in photosynthesis, the rates of the two processes are equal and their is no net release of either oxygen or carbon dioxide.

producers (autotrophs)

an organism which produces its own food

photoautotrophs (green plants, algae, etc)

make their own food from carbon dioxide and water using energy from sunlight

chemoautotrophs

make their own food from simple compounds such as ammonia, hydrogen sulphide or methane, not requiring sunlight

consumers (heterotrophs)

obtain their food by eating other organisms

food web

a complex network of interrelated food chains

ecological pyramids

quantitative models, usually measured for a given area and time. Includes pyramids of numbers, biomass and productivity

solar constant

the solar energy reaching the top of Earth's atmosphere (1400 J s-1 m-2 or 1400 watts per second)

productivity

the conversion of energy into biomass over a given period of time. It is the rate of growth or biomass increase in plants and animals. It is measured per unit area per unit time.

gross productivity (GP)

the total gain in energy or biomass per unit area per unit time

net productivity (NP)

the gain in energy or biomass per unit area per unit time that remains after deductions due to respiration

gross primary productivity (GPP)

the total gain in energy or biomass per unit area per unit time by green plants. It is the energy fixed by green plants by photosynthesis

net primary productivity (NPP)

the total gain in energy or biomass per unit area per unit time by

biomass

the living mass of an organism or organisms. Measured by obtaining the dry mass and usually calculated per unit area.

gross secondary productivity (GSP)

total energy or biomass assimilated (taken up) by consumers and is calculated by subtracting the mass of fecal loss from the mass of food eaten.

GSP = food eaten - fecal loss

net secondary productivity (NSP)

the total gain in energy or biomass per unit area per unit time by consumers after allowing fro losses to respiration.

NSP = GSP - R

nitrogen fixation

when atmospheric nitrogen (N2) is made available to plants in the form of ammonium ions

nitrification

the conversion of ammonium ions to nitrites (NO2-) and nitrites to nitrates (NO3)

denitrification

when bacteria convert ammonium, nitrites and nitrates back into atmospheric nitrogen

maximum sustainable yield (MSY)

the largest crop or catch that can be taken from a stock of a species ( a forest, or a a shoal of fish) without depleting the stock. Taken away is the increase in production of the stock while leaving the stock to reproduce again. Equivalent to the NPP or NSP of a system.

biome

a collection of ecosystems sharing similar climatic conditions

biosphere

that part of the Earth inhabited by organisms. It extends from the upper atmosphere down to the deepest parts of the oceans which support life.

zonation

the change in community along an environmental gradient due to factors such as changes in altitude, latitude, tidal level or distance from shore/coverage by water

succession

the process of change over time in an ecosystem involving pioneer, intermediate and climax communities

primary succession

occurs on a bare inorganic surface, involving the colonization of newly created land by organisms

secondary succession

when an already established community is destroyed. Occurs on soils that have already developed.

K-strategist

a species which have small numbers of offspring, invest highly in parental care, most offspring survive, good competitors, populations usually close to carrying capacity

r-strategist

a species which uses lots of energy in the production of vast numbers of eggs, no energy is used in raising offspring, reproduce quickly, able to colonize new habitats quickly, may exceed carrying capacity and then crash as a result

quadrat

a frame of specific size (depending on what is being studied) which may be divided into subsections

transect

a sample path/line/strip along which you record the occurrence and/or distribution of plants and animals in a particular study area

salinity

the concentration of salts expressed in 0/00 (parts of salt per thousand parts of water)

turbidity

the cloudiness of a body of fresh water

species diversity

a function of the number of species and their relative abundance

Simpson's diversity index

a calculation for biodiversity

lincoln index

a way to measure the abundance of small motile organisms

(catch 1 x catch 2) / marked in catch 2