populations Flashcards
what is the carbon cycle important for?
formation of complex organic molecules
what are the carbon stores?
oceans (dissolved in carbonate salts)
sediments e.g. limestone
fossil fuels
biomass
atmosphere
what happens to carbon during photosynthesis?
CO2 is removed from atmosphere by terrestrial plants
removed from ocean stores by aquatic plants
what happens to carbon during respiration?
CO2 is returned to the carbon stores in air and oceans
what happens to carbon during decomposition?
CO2 is released from dead organisms by saprotrophs
what happens to carbon during fossilisation?
formation of fossil fuels from dead ogranisms which have not decayed
formation of limestone
what happens to carbon during combustion?
carbon from fossil fuels returned to atmosphere
what is the greenhouse effect?
greenhouse gases let suns short wave radiation reach earth but trap some long wave radiation coming from warm earth
what are the main reasons for enhanced greenhouse effect?
burning fossil fuels
deforestation
methane increase due to rice crops, cattle and rotting materials in landfill
CFC’s
what are the consequences of global warming?
melting of polar ice caps
thermal expansion of water
increased frequency of droughts/hurricanes/forest fires
effects food production
habitat changes cause disruption of species
what is carbon footprint?
the total amount of CO2 attributable to the actions of an individual in the course of one year
what is the impact of agriculture fertilisers?
large amounts of nitrogen rich fertilisers needed for high yielding crops (NPK/manure)
if too much used or used before rainfall nitrates can leach into lakes and rivers causing eutrophication
what happens during eutrophication?
nitrates washed out of of soil (leaching)
nitrates in water cause rapid growth of algae
dense algal growth blocks out sunlight to submerged plants
plants and algae die
broken down bysaprotrophs that use up all O2
cause aquatic organisms to die
how does man affect nitrogen cycle?
ploughing soil increases O2 content
installing drainage systems
both encourage growth of nitrifying bacteria
lead to leaching
measures to reduce mans affect on nitrogen cycle?
restrict amount of fertilisers
crop rotation
avoid ploughing up established grassland
what is the nitrogen cycle?
the flow of inorganic and organic nitrogen containing compounds within abiotic and biotic compounds of an ecosystem
what is nitrogen needed for?
needed for making amino acids/proteins/ATP/nucleic acids
what is nitrogen fixation?
where nitrogen molecules found in atmosphere combine with other atoms
gets fixed when combined with oxygen or hydrogen
what are ways in which nitrogen can be fixed?
atmospheric fixation (lightening)
industrial fixation
biological fixation (free living and symbiotic relationship bacteria)
what is nitrification?
ammonium ions are oxidised into nitrite ions by nitrosomonas
nitrite ions are oxidised into nitrate ions by nitrobacter
what is the process by which ammonium ions are oxidised into nitrite ions?
nitrosomonas
what is the process by which nitrite ions are oxidised into nitrate ions?
nitrobacter
how do nitrate ions get into plants?
absorbed by plants and assimilated into organic nitrogen-containing molecules
what is ammonification?
decomposition by bacteria and fungi
detritivores break down amino acids from dead animals and plants, faeces and urine into ammonium ions
what is denitrification?
nitrate ions are reduced back into nitrogen gas
usually in water logged soil with anaerobic conditions
what is the rough cycle?
nitrogen fixing + decomposers make ammonium ions in soil
ammonium ions
nitrite ions
nitrate ions
absorbed by plants or denitrification back into atmosphere
animals and plants decay
repeat
what do free living bacteria do in soil?
have ability to combine nitrogen gas to form ammonium ions
what do symbiotic relationship bacteria do?
love in root nodules of legumes
nitrogen reduced to ammonium ions by nitrogenase
nodules contain haemoglobin which binds to oxygen to create oxygen free environment for enzyme to function in
what is an ecosystem?
a balanced biological system where all organisms and the non-living components interact in a particular location
what is a habitat?
place where an organism lives
what is a niche?
role and position of an organism within its environment including all interactions with biotic and abiotic factors in its environment
what are limiting factors?
aspects of environment which restrict population size
what are species?
group of organisms which share a large number of common characteristics and which can interbreed to produce FERTILE offspring
what is a population?
a group of organisms of a single species interbreeding and occupying a particular habitat
what is a community?
interacting populations of two r more species in the same habitat at the same time
what are factors affecting population size?
birth rate
death rate
immigration/emigration
what term should you use instead of birth rate for animals which aren’t mammals?
reproductive rate
what are the phases of animal population?
lag phase
log phase
stationary phase
what happens in the lag phase (animals)?
slow growth due to shortage of reproducing individuals
adaption to environment