b4 Flashcards
(29 cards)
biotic factors
living parts of an ecosystem
abiotic factors
non living parts of an ecosystem
stage 1 nitrogen cycle ugh
nitrogen is too unreactive to be used directly by plants to make a protein.
must be converted to soluble ions like nitrates. nitrogen fixing bacteria found in root nodules and free living in the soil are able to do this
so can lightning lol!
stage2 nitrogen cycle
nitrogen exists in the soil as nitrates dissolved in water
the water is taken up by the roots and the nitrates are used to make proteins
stage 3 nitrogen cycle
the excretion of urea (in animal urine) releases nitrogenous compounds into the soil.
bacteria in the soil make an enzyme called urease which converts urea to ammonia
nitrifyingbacteria convert the ammonia into nitrates which plants can absorb
stage 4 nitrogen cycle DEATH
decomposers break down the protein in the dead bodies of the animals and plants, converting it into ammonia
nitrifying bacteria then convert the ammonia into nitrite and then nitrates
stage 5 nitrogen cycle -release into atmosphere
denitrifying bacteria in the soil break down nitrates and return nitrogen gas into the air
occurs in anaerobic conditions
farmers try prevent denitrification as plants grow best when there are plenty of nitrates in soil
for them to use to make the proteins needed for growth
steps a farmer can take to prevent denitrification
plough the soil regularly to encourage aerobic conditions (get oxygen in)
drain any waterlogged areas
rotate crops by planting leguminous plants every few years
which have root nodules with nitrogen fixing bacteria that can convert the nitrogen gas directly from the air into nitrogenous compounds the plants can use, increasing soil fertility
stage 1 carbon cycle
carbon enters the atmosphere as co2 from respiration and combustion
stage 2 carbon cycle
carbon dioxide is absorbed by producers to make carbohydrates in photo synthesis
stage 3 carbon cycle
animals feed on plants, passing carbon compounds along the food chain
most carbon they consume is exhaled as co2 during respiration
the animals and plants eventually die
stage 4 carbon cycle
dead organisms are decomposed by bacteria and fungi
the carbon in their bodies is returned to the atmosphere as co2
under some conditions, decomposition is prevented and fossilisation takes place
combustion of here fossil fuels returns co2 to the air
returning co2 to the atmosphere
respiration
combustion
use / burnin of fossil fuels is gradually increasing co2 levels in atmosphere
decomposition releases co2
process happens faster in warm moist conditions with plenty of oxygen case it involves microorganisms
decay can be v slow in cold dry conditions and when there’s shortage of oxygen
nitrate fertilisers (5)- might as well be (50)
- increased nitrates from fertilisers in the water increase the growth of algae and plants
- the algae form a bloom over the water surface, preventing sunlight reaching other water plants
- these plants die cause theyre unable to carry out photosynthesis without light
- microbes such as bacteria increase in number as they decompose the dead plants, using and reducing the oxygen content in the water during respiration as they do so
- the low oxygen levels can cause aquatic insects and fish to suffocate, and eventually the lake may be left completely lifeless
what is an indicator species
an organism whose presence or absence is used by scientists to determine if an area is polluted
lichens-air pollution (grow on tree trunk)
commonly used to determine air pollution as many species will only grow in areas which are free of air pollutants such as those’d produced by traffic
water pollution- freshwater invertebrates
used to determine levels of pollution in fresh water
some organisms can tolerate high levels of pollution whereas others will not be found in polluted areas
pollution also indicated by acidic pH or lack of oxygen in water
what is a pollutant
a chemical which contaminates the environment is called a pollutant
examples of pollutants
pesticides-used by farmers to prevent pests eating their crops
heavy metals- used in industry
bioaccumulation
the build up of toxins at higher trophic levels
pollutants in food chain-eutrophication
- pollutant washed into rivers/lakes
- enters the food chain by adhering to or being absorbed by producers
- when the producer is eaten, pollutant it contains is passed onto the next trophic level as its persistent
-remains in body tissues of organism as its not easily broken down - pollutant continues to accumulate, increasing in concentration as it moves up food chain
- by time it reaches top carnivore, the pollutant will have accumulated to such an extent that it becomes toxic, reducing fertility or causing death
DDT
chemical pesticide used by farmers to control insect pests eating their crops
used to demonstrate bioaccumulation
high concentrations of DDT in birds of prey weakened their egg shells, their young died and populations increased
why does level of atmospheric co2 vary
photosynthesis only takes place in the light so co2 is only removed from the atmosphere in the daytime
respiration is carried out by all living organisms throughout the day and night, releasing co2 at a relatively consistent rate
over past 200 years, average atmospheric co2 concentration has increased bare
due to human activities- combustion of fossil fuels + deforestation
=global warming
role of microorganisms in the cycling of materials through an ecosystem
microorganisms (like bacteria and fungi) are decomposers
break down dead organisms and waste, releasing nutrients like:
- carbon
-nitrogen
make nutrients available to producers, continuing food chain
