ecology
study of an organisms environment and the factors that determine it’s distribution and abundance.
environment
abiotic factors of ecosystem
population
all the organisms of a particular species living in an ecosystem at a particular time
community
all of the populations of living organisms living in an ecosystem at a particular time
habitat
place where specific organisms live
ecosystem
self supporting system of organisms interacting with each other and with their physical environment
quadrats
used to sample the distribution of organisms in their habitats, and to estimate the population size of an organism in different areas
what does biotic mean
living (factors)
what does abiotic mean
non-living (factors)
what is the word equation for photosynthesis
water + CO2 (+light) –> glucose + O2
what is the chemical equation for photosynthesis
6CO2 + 6H2O ——-> 6O2 + C6H12O6
how much energy is passed from one trophic level to the next
10%
what are the different trophic levels of a food chain/web
producers, primary, secondary and tertiary consumers and decomposers
where is the ORIGINAL source of energy in food chains/webs
the sun, producers convert this light energy to chemical energy through photosynthesis and consumers gain it through consumption.
producer
an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis
consumer
an organism that gets its energy by feeding on other organisms. also known as heterotrophs
what is a trophic level
position of an organism in a food chain or food web
decomposer
an organism that gets its energy from dead waste or organic matter
what is a food chain
a chart showing the flow of energy/food from one organism to the next beginning with the producer
what is a food web
a network of interconnected food chains showing the energy flow through that part of the ecosystem
what do arrows represent in a food web
the flow of energy
how much energy is lost from the sun to the producer
99%
where does the 99% of energy lost from the sun to the producer go to
over 90% is reflected by the atmosphere
not all sunlight will fall on a producer
some sunlight will pass through leaves without hitting a chloroplast (transmission)
some light is the wrong wavelength (green light is converted)
some light is converted to heat during photosynthesis and respiration
some light energy is used to evaporate water from leaves
where does the 90% of energy lost from one trophic level to the next go to
not all of organism is eaten, e.g. bones
some of the organism may not be digested and will be lost in digestion e.g. humans dont digest cellulose
much energy is lost as heat in cellular respiration to carry out MRSGRENC
why are food chains not super long
the continual energy loss puts a limit on the number of trophic levels that can be supported with enegry through a food chain
what is a quadrat
it is a square that marks off an exact area so that plants in that area can be identified and counted
what are decomposers
organisms such as bacteria and fungi that break down and decompose dead material and waste products to recycle the nutrietns
what is the population size of the organisms in an ecosystem affected by
the physical environment such as temperature, rainfall and amount of sunshine
what does the water cycle involve
evaporation, transpiration, condensation, and precipiation
how much carbon dioxide is in the air
around 0.04%
what is the equation for combustion
fuel + O2 –> CO2 + H2O
biodiversity
amount of variation of species in an ecosystem
how do you measure biodiversity
- number of different species (species richness)
2. abundance of each species
types of interactions in ecosystems
- feeding between trophic levels
- competition between organisms (e.g. for light, water or nesting sites)
- interaction with abiotic factors (e.g. animals using materials to build shelters
examples of abiotic factors
amount of nitrogen in soil pH of soil temperature wet or dry soil pollutants
examples of biotic factors
change in amount of predators
decreased food availability
disease (e.g bacteria, viruses)
what does nitrifying bacteria do
turn ammonia into nitrates
what does denitrifying bacteria do
turn nitrates into N2 or nitrogen in the air
what does nitrogen fixing bacteria do
turn nitrogen in the air into nitrates. (there is one type in the roots of legumes and one type in the soil)
what is the role of decomposers in the nitrogen cycle
recycling proteins
are nitrates soluble
yes
name two things we need nitrogen for
DNA
proteins / enzymes
what are the three ways nitrogen can get back into the soil
lightning (there is enough energy to react the hydrogen and oxygen) nitrogen fixing bacteria (the two types) artificial fertilisers (Haber process)
what are legumes, give examples
anything with a pod e.g peas, beans, clovers
what is the symbol for ammonia
NH3
how are soil ions controlled by farmers and why
by adding fertilisers to the soil or growing it in a hydroponic culture to make proteins and other compounds for growth
how is soil structure controlled by farmers and why
ploughing fields to break up compacted soil; adding manure to improve drainage and aeration of heavy, clay soils. this is for better uptake of mineral ions by active transport and water
how is soil pH controlled by farmers and why
adding lime to acidic soils; few soils are too alkaline to need treatmenet. this is because soil pH can affect crop growth as un unsuitable pH reduces uptake of mineral ions
how is carbon dioxide, light and heat controlled by farmers and why
not in a field but in a greenhouse, they can all be altered to maximise crop yield. burning fuels produce heat and carbon dioxide. these limit the rate of photosynthesis and production of organic substances needed for growth, so farmers want to control them.
why would a farmer use a greenhouse
they can control factors to maximise crop yield:
high humidity for low water loss
heaters produce CO2 needed for photosynthesis
transparent walls allow for natural light
optimum temperature
NITROGEN AND CARBON CYCLE
.
what are organic fertlisers made of
faeces of farm animals mixed with straw
what are inorganic fertilsers made of
inorganic compounds such as potassium nitrate or ammonium nitrate formulated to give plants a specific amount of ion like nitrate
how would a farmer increase nitrataes in his soil
inorganic fertlisers or grow a legume crop like clover in a field one year in four. legumes have nitrogen fixing bacteria in odules on their roots which convert nitrogen gas to ammonium ions. theyre ploughed back into the soil and by next year it has been oxidised to nitrate by nitrifying bacteria
how can a pest harm a crop
lowering yield by reducing the growth
affecting the appearance or quality of crop making it unsellable
why does a farmer use pesticides
improve yield
problems with pesticides
slow to decompose
bioaccumulation
biomagnefication
kill other harmless insects
an ideal pesticide should
control the pest effectively be biodegradable be specific so only pest is killed not cause bioaccumulation be safe to transport be easy to apply
why was DDT banned
it remained active in the environment for many years and didn’t fully decompose for over 10 years
insects became immune to it
kills any type of insect
very soluble in fats
what is biological control
it uses another organism to reduce the numbers of a pest
examples of biological control
introducing a natural predator introducing a herbivore introducing a parasite introducing a pathogen introducing sterile males using pheromones
pollution def
the contamination of the environment by harmful substances that are produced by the activities of humans.
how has CO2 increased
burning fossil fuels and gas.
deforestation
what are the greenhouse gases
CO2 water vapour methane nitrous oxide chloroflurocarbons
greenhouse effect
short-wavelength infrared radiation strikes the earth, some energy is absorbed. the radiation is re-emitted as longer wave radiation.
some long wavelength IR radiation from earth escapes into space.
some short-length IR radiation from earth is absorbed by the greenhouse fases and re-emitted back to earth.
impacts of global warming
polar ice caps melt and sea levels rise
change in major ocean currents
change in global rainfall patterns
change the nature of manty ecosystems e.g. migration of birds
changes in farming practices necessary as pests became more abundant.
when is carbon monoxide formed
when substances containg carbon are burned in a limited supply of oxygen.
why is carbon monoxide dangerous
colourless odourless tasteless can be fatal haemoglobin binds more strongly with it than oxygen (carboxyhaemoglobin), reducing the blood's capacity to carry oxygen.
when is SO2 formed
when fossil fuels are burnt and combines with water droplets in the air
danger of SO2
it can be carried as acid rain which leads to acidifcation of lakes, soil and the death of conifers.
what organism indicates levels of sulfur dioxide pollution
lichen
DEFORESTATION
PAPER 2
what is sewage
wet waste from houses, factories and farms.
if sewage is discharged untreated into waterways what problems does it cause
aerobic bacteria polluted so the lack of oxygen causes animals in freshwater to die.
contains pathogenic bacteria, which are a danger to human health
aim of sewage treatment
to remove solid and suspended organic matter and pathogenic microorganisms so that cleaner waste can be discharged into waterways
what is eutrophication ususally caused by
an inorganic mineral ion, nitrates or phosphates from sewage or fertilisers
eutrophication
artifical fertlisers containing nitrates or phosphates are washed out of soil by rain (leaching) into waterways. the excess mineral ions stimulate the growth of all plants but paticularly algae, (algal bloom). the algae soon start to die and are decomposed by the aerobic bacteria. this uses so much oxygen in the water (and they have no light due to the algae) that fish and other aerobic animals die.
what is biodiversity a measure of
the number of different species present (species richness)
the relative abundance of each species (their evenness ofnumbers)
is biodiviersity a good thing for the environment
generally yes because they are often more stable, as an ecological disaster will not affect the entire ecosystem
example of ecological disaster
disease (could wipe out food sources but a ecosystem rich with biodiversity would not lose all food)
where is nitrogen present
many biological compounds: proteins amino acids most vitamins DNA and ATP
what does the nitrogen cycle involve
feeding, assimilation, death and decay.
why are photosynthesis and respiration not involved in the nitrogen cycle
they contribute to the carbon cycle
how does feeding and assimilation contribute to the nitrogen cycle
pass nitrogen atoms already in organic compounds along food chains
how does decomposition contribute to the nitrogen cycle
fungi and bacteria produce ammonia from the nitrogen in compounds like proteins, DNA and vitamins
how does nitrification contribute to the nitrogen cycle
the ammonia is first oxidised to nitrite and then to nitrate by nitrifying bacteria.
how do plants contribute to the nitrogen cycle
their roots can absorb the nitrates. they are combined with carbohydrates (from photosynthesis) to form amino acids and then proteins, as well as other nitrogen-containing compounds
how does denitrification contribute to the nitrogen cycle
denitrifying bacteria use nitrates as an energy source and convert them into nitrogen gas. denitrification reduces the amount of nitrate in the soil.
how do nitrogen-fixing bacteria in soil contribute to the nitrogen cycle
they convert nitrogen gas to ammonia. this is used by bacteria to make amino acids and proteins. when bacteria die, their proteins decompose, releasing ammonia back into the soil.
how do nitrogen fixing bacteria in root nodules contribute to the nitrogen cycle
make ammonia but this is converted by the plant into amino acids and other organic nitrogen compounds. death and decomposition of the plant returns to the nitrogen to the soil as ammonia
how does lightning contribute to the nitrogen cycle2
it converts nitrogen gas in the air into oxides of nitrogen. these dissolve in rainwater, enter the soil and are converted to nitrates by nitrifying bacteria
how do humans contribute to the nitrogen cycle
we make nitrates industrially from nitrogen gas. these are mainly used as fertilisers because they increase the rate of growth of crops.
why do carbon levels in the environment fluctuate
in the winter, trees do not have leaves and so cannot photosynthesise. they still respire which produces carbon dioxide. so in the winter months they give out more carbon dioxide then they take in. in the summer months, they have many leaves and can photosynthesise, therefore taking in more carbon dioxide than they produce. (altough still respiring) howver because there are fewer trees overall, it does not fully return to that level of last summer.
when is methane produced
when microorganisms ferment larger organic molecules to release energy.
most significant sources of methane
decomposition of waste buried in the ground (landfill sites) by microorganisms
fermentation by microorganisms in the rumen (stomach) of cattle and other rumeninants
fermentation by bacteria in rice fields
which molecule is contributes to the greenhouse effect more, methane or carbon dioxide
methane. although there is less in the atmosphere, each molecule has a much bigger greenhouse effect.
where do tropical rainforests form
around the equator, south america, central africa and indonesia
what is slash and burn
the method where trees are cut down and burned
why does deforestation occur
to provide wood (timber) for furniture or buiding etc, and to clear land for farming.
effects of deforestation
destruction of habitats and reduced biodiversity. 50-70% of species live in rainforests.
reduced soil quality. no trees and other plants to return minerals to the soil when they die, and no tree roots to hold the soil together. crops planted in deforested areas rapidly use up the minerals and the rest is leached by rain.
the soil is exposed due to lack of tree cover (canopy) and is blown or washed away.
deforesttion may produce climate change. trees reuturn water vapour from soil to the air by transpiration through thier leaves. cutting down the forests will upset the water cycle.
rainforests a valuable source of medicinal drugs and plants cultivated as crops. unknown ones will belost
what is sustainable production
replacing the trees that have been removed and ensuring that there is no ecological damage.
examples of controlled replanting schemes
reforestation or re-afforestation
why is tackling the farming on this land a complex issue
large scale cattle farming and palm oil for cosmetics could be stopped.
however smaller farmers may depend on this for their and their families livelihood - one solution is to give them m financial help to establish farms in other areas.
