Population and Ecosystems Flashcards
What is a population?
The number of organisms of one species living in a particular habitat.
What is a community?
The number of different species living in a particular habitat.
What is a habitat?
A specific area where an organism lives.
What is an environment?
Conditions that an organism experiences.
Give examples of biotic factors
Living factors, such as disease, predation, population, competition and habitat.
Give examples of abiotic factors
Non-living factors, such as oxygen concentration, soil acidity, light and temperature.
What is an ecosystem?
A biological community made up of biotic and abiotic factors. Each has distinctive features and they are dynamic (subject to change).
What is a niche?
Each organisms role in an ecosystem (predator, prey, producer, decomposer). Only one species can occupy a particular niche in a particular habitat, due to interspecific competition.
What are factors increasing population size?
Birth rate and immigration rate.
What are factors decreasing population size?
Death rate and emigration rate.
What is the carrying capacity?
The maximum number of organisms a habitat is able to contain.
Describe the lag phase of a population in a natural environment and laboratory
Natural environment: The time taken for animals to reach sexual maturity, find mates and complete gestation.
Laboratory: Enzymes are being synthesised and DNA is being replicated.
Describe the log phase of a population in a natural environment and laboratory
Natural environment: Births + Immigration > Death + Emigration. Food, space and mates are plentiful.
Laboratory: Cell division > Cell death. No limiting factors, nutrients and space is plentiful.
Describe the stationary phase of a population in a natural environment and laboratory
Natural environment: Births + Immigration = Death + Emigration. Fluctuation around the carrying capacity due to predation and competition.
Laboratory: Cell division = Cell death. Nutrients are starting to deplete and waste products build.
Describe the death phase of a population in a natural environment and laboratory
Natural environment: Births + Immigration < Deaths + Emigration. Crash generally due to density independent factors.
Laboratory: Cell division < Cell death. Nutrients are depleted and toxic waste products build.
What are the four stages in a population growth graph?
Lag phase
Log phase
Stationary phase
Death phase
Give examples of density dependant factors
Environmental factors that affect a greater proportion of the population if it is denser (mostly biotic), such as predation, competition for food, space and mates.
Give examples of density independent factors
Environmental factors that will affect the death rate regardless of the population (mostly abiotic), such as natural disasters and climate change.
What is intraspecific competition?
Competition for resources within the same species.
What is interspecific competition?
Competition for resources between different species.
Why is not all incident light from the sun used for photosynthesis by producers?
The light is the wrong wavelength
The light is reflected from the leaf surface
The light is not hitting a chloroplast
What is gross primary productivity (GPP)?
The rate at which light energy is converted to chemical energy by photosynthesis.
What is net primary productivity (NPP)?
The rate at which biomass is accumulated.
How do you work out NPP?
Gross primary productivity (GPP) - Respiration (R).
What is secondary productivity?
The rate at which consumers accumulate energy from their surroundings.
How to calculate photosynthetic efficiency in plants?
(Gross primary productivity (GPP) ÷ Total incidental sunlight) x100
How to calculate efficiency of energy transfer in consumers?
(Energy in biomass ÷ Energy consumed) x100
How is energy lost throughout the food chain?
Energy is lost as heat through respiration.
Energy is lost to surroundings through excretion and egestion.
What is biomass?
The dry mass of all living material present in a particular organism or area.
How to measure biomass?
Count the individuals at each trophic level and multiply by an average individual mass.
What is an ecological pyramid?
A diagram that shows the relative amounts of energy or biomass or numbers of organisms within each trophic level in a food chain.
What are the three types of ecological pyramids?
Pyramid of numbers
Pyramid of biomass
Pyramid of energy
What are disadvantages to using a pyramid of numbers?
They do not take size of organisms into account
They can’t be represented on the same scale for each level
They do not take into account juvenile forms
What are disadvantages to using a pyramid of biomass?
They don’t account for seasonal changes.
What are pyramids of biomass measured in?
Land- kgm-2
Water- kgm-3
What are pyramids of energy measured in?
KJm-2y-1
What is ecological succession?
A gradual change in the structure and species composition of a community over time.
What is primary succession?
Colonisation of bare rock where there has been no previous habitation.
What is secondary succession?
Colonisation of an area that has been previously habited and soil is already present.
What are seres?
Stages in succession where particular communities dominate.
What is a pioneer species?
The first species to colonise an area. They are adapted to tolerate harsh, abiotic conditions.
How is lichen a pioneer species?
It secretes acid which breaks down rock and builds up soil.
What is facilitation?
Where plants and animals build up the soil by adding nutrients through decomposition, improving abiotic conditions over time. This allows immigration of new plants and animals into the area.
What is the climax community?
The final stable community in succession. Usually where biodiversity is the highest.
What is the effect on biodiversity in succession?
Biodiversity increases throughout succession. The increased diversity of plants increases the diversity of animals as there is more food and habitat.
What aspects contribute to CO2 in the atmosphere?
Plant respiration
Animal respiration
Saprotroph respiration
Fossils fuel combustion
What is partial decay?
The decomposition of remains of plants, used in fossil fuels.
What are detritivores?
Animals that eat detritus (earthworms and woodlice).
What are saprotrophs?
Microbes that live on detritus (fungi and bacteria).
What is the effect of combustion of fossil fuels on the environment?
It increases global warming, leading to climate change.
Give examples of climate change affecting biodiversity
Extreme weather (droughts and floods)
Sea level and temperature rise
Migration towards the poles
What farming practices are implemented as a result of climate change?
Planting drought tolerant crops
Drip irrigation to conserve water
Low emission farm vehicles
Farms receiving payment for planting trees
What is a carbon footprint?
The total amount of CO2 attainable to the actions of one individual, product or service over a year.
What are the four inorganic forms of nitrogen in the nitrogen cycle?
Ammonium (NH4+)
Nitrites (NO2-)
Nitrate (NO3-)
N2 in the atmopshere
Describe the nitrogen fixation process
By soil bacteria- using azotobacter to turn N2 in the atmosphere into NH4+.
By legumes- using rhizobium in the root nodules of legumes to turn N2 in the atmosphere into proteins and DNA in the plant.
Describe the nitrification process
Converting NH4+ to NO2- using nitrosomonas bacteria and converting NO2- to NO3- using nitrobacter bacteria. Requiring aerobic conditions.
Describe the denitrification process
Converting NO3- to N2 in the atmosphere using pseudomonas bacteria. Requiring anaerobic conditions.
Describe the ammonification process
Converting nitrogen in dead tissues and excretory products into NH4+ using decomposers and saprophytes.
Describe the assimilation of organic nitrogen in plants
Plants take in nitrates (NO3-) by facilitated diffusion or active transport by roots and assimilate it into proteins and DNA.
Describe the assimilation of organic nitrogen in animals
Animals eat plants and assimilate organic nitrogen into proteins, DNA and urea.
What is the effect of ploughing and drainage on crop yield?
It prevents denitrification which occurs in waterlogged, unploughed soil.
What is the effect of manure and slurry on crop yield?
It is used as a less soluble form of fertiliser and has a smaller chance of leaching.
What is the effect of nitrogen-fixing crops on crop yield?
Legumes convert nitrogen into amino acids to allow nitrogen rich soil for new crops after their decomposition.
What is the effect of artificial fertiliser on crop yield?
It has a rapid uptake and effect, increasing growth which increases crop yield.
How do drainage ditches damage habitats?
They destroy habitats and decrease biodiversity.
How do grasslands damage habitats?
Excess nitrates increases the growth of weeds which outcompete other species, decreasing biodiversity.
How does eutrophication damage habitats?
If fertiliser leaches into rivers and lakes in can cause algal bloom. This prevents light from reaching aquatic plants, so they die and decompose. Bacteria then multiply and respire, stripping the lake of sufficient oxygen, so the ecosystem deteriorates.
