3.5 - Population Size and Ecosystems Flashcards
What are abiotic factors?
The non-living aspects of an ecosystem (e.g. light, temperature, water availability, oxygen availability and soil pH)
What is an abundance?
The number of individuals per species in a specific area at a given time
What is ammonification?
The production of ammonium compounds when decomposers feed on organic nitrogen-containing molecules
What is Azotobacter?
A type of nitrogen-fixing bacteria that lives freely in the soil
Define belt transect
A line along a sampled area upon which quadrats are placed at intervals to determine the abundance and distribution of organisms in an ecosystem
What is biomass?
The total mass of organic material, measured in a specific area over a set time period
What are biotic factors?
The living components of an ecosystem (e.g. food availability, pathogens, predators and other species)
What is birth rate?
The number of offspring born per thousand of population per year
What is the carbon cycle?
The cycle through which carbon (in the form of CO2) moves between living organisms and the environment, involving respiration, photosynthesis and combustion
Define 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.
What is climax community?
The stable community of organisms that exists at the final stage of ecological succession
Define colonisation
The occupation of a new species in a location
What is a community?
All of the populations of different species living together in a habitat
Explain the term competition
When different organisms compete for the same resources (e.g. light, water, mates, territory) in an ecosystem. This limits population sizes.
Define death rate
The number of deaths per thousand of population per year
What is deforestation?
The removal of trees from land which is subsequently used to grow crops or provide space for livestock or construction.
What is denitrification?
The conversion of of nitrate ions to nitrogen gas by denitrifying bacteria
What does denitrifying bacteria mean?
Anaerobic micro-organisms found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas
What are density-dependent factors?
Factors whose effects on population size differ with population density (e.g. competition, predation, disease)
What are density-independent factors?
Factors which effects on population size remain the same regardless of population density (e.g. climate)
What are detritivores?
Organisms that feed on dead organic matter
What does distribution mean?
The spread of living organisms in an ecosystem
Define ecology
The study of the relationships among organisms and their environment
Define ecosystem
The community of organisms (biotic) and non-living (abiotic) components of an area and their interactions
Define efficiency of energy transfer
The efficiency of energy transfer between trophic levels, calculated using:
Efficiency = energy available after transfer / x100
energy available before transfer
What is Emigration?
The numbers of individuals leaving a region per thousand of population per year
What is eutrophication?
The process by which pollution by nitrogen-containing fertilisers result in algal blooms and subsequent oxygen level reduction in bodies of water
Define extinction
The death of all living members of a species
What are fertilisers?
Natural or artificial materials that are added to soils to provide essential nutrients and improve plant growth
Define global warming
The gradual rise in the average temperature of the Earth due to increasing atmospheric levels of carbon dioxide and methane gas
What is the greenhouse effect?
The increase of global temperatures caused by the trapping of solar heat by gases in the atmosphere
Explain what gross primary productivity (GPP) means
The rate of chemical energy fixture during photosynthesis by all producers in an ecosystem, measured in KJ-2 year-1
What does habitat mean?
The region where an organism normally lives
Define immigration
The number of individuals entering a region per thousand of population per year
What is lag phase?
A period of slow population growth
What is 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.
Define log phase
A period of rapid population growth in which birth rate exceeds the death rate. Also known as the exponential phase.
What is 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:
NPP = gross primary production (GPP) - respiartory losses (R)
What does niche mean?
Describes how an organism ‘fits’ into an ecosystem and its role to that environment
What is nitrification?
The conversion of ammonium ions to nitrate ions by nitrifying bacteria. This takes place in two stages: ammonium ions are oxidised to nitrite ions; nitrite ions are oxidised to nitrate ions.
What are nitrifying bacteria?
Aerobic micro-organisms found in the soil responsible for the oxidation of ammonium ions to nitrate ions
What is Nitrobacter?
A genus of nitrifying bacteria that oxidises nitrites into nitrates
What is the nitrogen cycle?
The cycle through which nitrogen moves between living organisms and the environment, involving ammonification, nitrification, nitrogen fixation and denitrification
What is nitrogen fixation?
The conversion of atmospheric nitrogen gas into ammonia by nitrogen-fixing bacteria in the soil or root nodules of legumes
What are nitrogen-fixating bacteria?
Micro-organisms responsible for the conversion of atmospheric nitrogen gas into nitrogen-containing compounds. They can be free-living or mutualistic
What is Nitrosomonas?
A genus of nitrifying bacteria that oxidises ammonium compounds into nitrates.
What are pioneer species?
Species that can survive in hostile environments and colonise bare rock or sand (e.g. lichens)
Explain what the term population means?
All organisms of the species living with one another in a habitat at the same time
What is primary succession?
A type of succession in which pioneer species colonise a newly formed or exposed area of land
What are producers?
Photosynthetic organisms at the start of the food chain that manufacture biomass for all living things
What is a pyramid of biomass?
A table of the dry mass of living material at each trophic level of a food chain. This forms the shape of a pyramid.
What is a quadrat?
A single square grid of known area used in sampling to determine the abundance of organisms in a habitat
What is random sampling?
A sampling technique use to avoid bias (e.g. creating a square grid and generating random coordinates
What is Rhizobium?
A type of nitrogen-fixing bacteria that lives inside the root nodules of leguminous plants
What are saprotrophs?
Organisms that feed by extracellular digestion. They release enzymes which catalyse the breakdown of dead plant and animal material into simpler organic matter
Define secondary succession
A type of succession in an ecosystem progressing towards a climax community
Explain what the term soil aeration means
The exchange of oxygen between the soil and atmosphere to produce the aerobic conditions required for nitrification. Human activities such as drainage an ploughing are used to improve aeration
What is the stationary phase?
A period of stability in which population numbers remain constant
What is succession?
Describes changes in the community of organisms occupying a certain area over time
What is 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.
Define trophic level
The position that an organism holds in a food chain, food web, pyramid numbers or pyramid of biomass.
