Populations Flashcards
Define ecology
The study of the relationships between living organisms, including humans, and their physical environment.
Define ecosystem
A balanced biological system where all the organisms (community) and the non-living components interact in a particular location. There is energy flow and nutrient cycling within the ecosystem.
Define community
Interacting populations of two or more species in the same habitat at the same time.
Define habitat
The place where an organism lives.
Define population
A group of organisms of a single species, interbreeding and occupying a particular habitat.
Define environment
The factors in a habitat which affect an organism - both living (biotic) and non-living (abiotic).
Define niche
The role and position of an organism within its environment, including all interaction with the biotic and abiotic factors of its environment.
When will population size increase? (equation)
reproduction + immigration are greater than deaths + emigration.
List the four stages of a population growth curve
Lag, log/exponential, stationary, death/decline
What is carrying capacity?
The maximum number of individuals a habitat/environment can sustain
What causes the lag phase in a bacterial fermenter?
Enzymes are being synthesised
What could cause the death phase in a bacterial fermenter?
Accumulation of toxic waste, or resources run out (glucose or O2)
Define a density dependent factor
A factor that affects population size and is affected by population size
Define a density independent factor
A factor that affects population size and is not affected by population size
What is the ultimate source of energy for most ecosystems?
The sun
What is the difference between inter and intraspecific competition?
Inter is between species, intra is within one species
Why is photosynthetic efficiency not 100?
Sunlight misses the leaves, is transmitted, is reflected, is the wrong wavelength, is not absorbed by the chloroplasts.
Give the assumptions made during capture mark recapture (Lincoln Index)
No migration, birth or death, marked individuals distribute themselves evenly, the marking does not increase likelihood of death from predators and is not toxic
Define GPP
Gross Primary Productivity is is the rate of production of chemical energy in organic molecules by photosynthesis in a given area. The unit is kJ m-2 year-1
Define NPP
NPP (kJ m-2) = GPP - energy used by plants in respiration. This is the energy available to primary consumers
Why is energy lost between trophic levels?
Some tissues are not eaten or are indigestible (egested), energy is lost in respiration and excretory products
Why are carnivores more efficient than herbivores?
Meat contains protein and fat, which are easier to digest than plant material
How do you calculate the efficiency of energy transfer between trophic levels?
Energy in biomass after transfer/energy available before transfer x 100
Define primary succession
Succession in a habitat that has never before been colonised. Bare rock- no soil/seeds/humus present
Define secondary succession
The reintroduction of organisms into an area that was previously colonised. Soil, seeds and humus are already present
The first plants to grow in a new habitat during succession are called?
Pioneer species
What are the stages in succession called?
Seral stages/seres
What is the climax community?
The final stable collection of plants and animals that succession produces. Equilibrium has been reached
List the five key processes by which carbon moves through the carbon cycle
Photosynthesis, respiration, combustion, decomposition, fossilisation
What is a carbon footprint?
The equivalent amount of CO2 generated by an individual a product or a service in a year.
What do plants need nitrogen for?
Synthesising amino acids, nucleic acids and chlorophyll
Give two forms of nitrogen that plants can take up
NO3- NO2- NH4+(nitrate, nitrite, ammonium)
Name the process that converts atmospheric nitrogen to ammonium or nitrate
Nitrogen fixation
What process can fix atmospheric nitrogen to form nitrate?
Lightning
Name the two bacteria that perform nitrogen fixation
Azotobacter (free living) Rhizobium (root nodules of legumes)
Name the process that converts ammonium to nitrate
Nitrification
Which bacterium converts ammonium to nitrite?
Nitrosomonas
Which bacterium converts nitrite to nitrate?
Nitrobacter
Name the process that returns nitrate to atmospheric nitrogen
Denitrification
Which bacterium performs denitrification and where is it found?
Pseudomonas and waterlogged soil/anaerobic conditions
List the steps in eutrophication
Leaching of fertilisers into water, algal bloom, plants/algae die, bacteria decompose them and use up O2, animals die
What is the effect of ploughing on soil?
Ploughing aerates the soil, increasing nitrification and decreasing denitrification
