Population size and ecosystems terms Flashcards
Abiotic factors
The non-living aspects of an ecosystem e.g. light, temperature, water availability, oxygen availability and soil pH.
Abundance
The number of individuals per species in a specific area at any given time.
Ammonification
The production of ammonium compounds when decomposers feed on organic nitrogen-containing molecules.
Azotobacter
A type of nitrogen-fixing bacteria that lives freely in the soil.
Belt transect
A line along a sampled area upon which quadrants are placed at intervals to determine the abundance and distribution of organisms in an ecosystem.
Biomass
The total mass of organic material, measured in a specific area over a set time period.
Biotic factors
The living components of an ecosystem e.g. food availability, pathogens, predators and other species.
Birth rate
The number of offspring born per thousand of population per year.
Carbon cycle
The cycle through which carbon (in the form of carbon dioxide) moves between living organisms and the environment, involving respiration, photosynthesis and combustion.
Carrying capacity
The average size of a population that can be supported by an ecosystem over extended periods of time. This varies depending on biotic and abiotic factors.
Climax community
The stable community of organisms that exists at the finals stages of ecological succession.
Colonisation
The occupation of a new area by a species.
Community
All of the populations of different species living together in a habitat.
Competition
When different organism compete for the same resources (e.g light, water, mates, territory) in an ecosystem. This limits population sizes.
Death rate
The number of deaths per thousand of population per year.
Deforestation
The removal of trees from land which is subsequently used to grow crops or provide space for cattle.
Denitrification
The conversion of nitrate ions to nitrogen gas by denitrifying bacteria.
Denitrifying bacteria
Anaerobic microorganisms, found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas
Density-dependent factors
Factors whose effects on population size differ with population density e.g. competition, predation, disease.
Density-independent factors
Factors whose effects on population size remain the same regardless of population density e.g. climate
Detritivores
Organisms that feed on dead organic matter.
Distribution
The spread of living organisms in an ecosystem
Ecology
The study of the relationships among organisms and their environment
Ecosystem
The community of organisms (biotic) and non-living (abiotic) components is an area and their interactions.
Efficiency of energy transfer
The efficiency of energy transfer between trophic levels is calculated using:
Efficiency= energy available after transfer/ energy available before transfer x100
Emigration
The number of individuals leaving a region per thousand of population per year.
Eutrophication
The process by which pollution by nitrogen- containing fertilisers results in algae blooms and subsequent oxygen level reduction in bodies of water.
Extinction
The death of all living members of a species.
Fertilisers
Natural or artificial materials that are added to soils to provide essential nutrients and improve plant growth.
Global warming
The gradual rise in the average temperature of the Earth due to increasing atmospheric levels of carbon dioxide and methane gas.
Greenhouse effect
The increase of global temperatures caused by the trapping of solar heat by gases in the atmosphere.
Gross primary productivity (GPP)
The rate of chemical energy fixture during photosynthesis by all producers in an ecosystem, measured in KJ m-2 year-1
Habitat
The region where an organism normally lives.
Immigration
The number of individuals entering a region per thousand of population per year.
Lag phase
A period of slow population growth
Line transect
A line along a sampled area. The species touching the transect at regular intervals are recorded to determine the abundance and distribution of organisms in an ecosystem.
Log phase
A period of rapid population growth in which birth rate exceeds death rate. Also known as the exponential phase.
Net primary production (NPP)
The amount of chemical energy that is available to heterotrophs in an ecosystem. It is calculated by subtracting chemical energy generated in respiration (R) from gross primary production:
Net primary production (NPP)= gross primary production (GPP)- respiratory losses (R)
Niche
Describes how an organism ‘fits’ into an ecosystem and its role in that environment.
Nitrification
The conversation of ammonium ions to nitrate ions by nitrifying bacteria. This takes place in two stages: ammonium ions are oxidised to nitrate ions; nitrate ions are oxidised to nitrate ions.
Nitrifying bacteria
Aerobic microorganisms found in the soil responsible for the oxidation of ammonium ions to nitrate ions.
Nitrobacter
A genus of nitrifying bacteria that oxidises nitrites into nitrates
Nitrogen cycle
The cycle through which nitrogen moves between living organisms and the environment, involving ammonification, nitrification, nitrogen fixation and denitrification.
Nitrogen fixation
The conversion of atmospheric nitrogen gas into ammonia by nitrogen-fixing bacteria in the soil or root nodules of legumes.
Nitrogen-fixing bacteria
Microorganisms responsible for the conversion of atmospheric nitrogen gas into nitrogen-containing compounds. They can be free-living or mutualistic
Nitrosomans
A genus of nitrifying bacteria that oxidises ammonium compounds into nitrites.
Pioneer species
Species that can survive in hostile environments and colonise bare rock or sand e.g. lichens.
Population
All organisms of the same species living with one another in a habitat at the same time.
Primary succession
A type of succession in which pioneer species colonise a newly formed or expose area of land.
Producers
Photosynthesis organisms at the start of the food chain that manufacture biomass of all living things.
Pyramid of biomass
A table of the dry mass of living material at each tropic level of a food chain. This forms the shape of a pyramid.
Quadrat
A square grid of known area used in sampling to determine the abundance of organisms in a habitat.
Random Sampling
A sampling technique used to avoid bias e.g. creating a square grid and generating random coordinates.
Saprotrophs
Organisms that feed by extracellular digestion. They release enzymes which catalyse the breakdown of dead plant and animal material into simple organic matter.
Secondary succession
A type of succession in which a habitat is re-colonised after a disturbance
Seres
Various intermediate stages in succession in an ecosystem progressing towards a climax community.
Soil aeration
The exchange of oxygen between the soil and atmosphere to produce the aerobic conditions required for nitrification. Human activities such as drainage and ploughing are used to improve aeration.
Stationary phase
A period of stability in which population numbers generally remain constant.
Succession
Describes changes in the community of organisms occupying a certain area over time.
Systematic sampling
A sampling technique used to determine the abundance and distribution of organisms along an area at periodic intervals e.g. along a belt transect. This is commonly used in ecosystems where some form of gradual change occurs.
Trophic level
The position that an organism holds in a food chain, food web, pyramid of numbers or pyramid of biomass.
