M6, C23 Ecosystems Flashcards
define ecosystem
all the organisms living in a certain area and all the non-living conditions found there
what are biotic factors
The living features of an ecosystem
eg. predators or food
what are abiotic factors
The non-living features of an ecosystem.
eg. temperature, rainfall, pH, soil nutrient availability
define habitat
the place where an organism lives within an ecosystem
How does light intensity affect an ecosystem
It affects the growth of producers.
Determines the rate of photosynthesis in plants.
how does temperature affect an ecosystem
affect the growth of producers (rate of photosynthesis)
could provide better/worse living conditions for organisms
why do we say that ecosystems are dynamic systems
the biotic and abiotic factors are always changing
how does water availability affect an ecosystem
affects photosynthesis in plants (producers)
water organisms need a plentiful supply of water to survive
how does oxygen availability affect an ecosystem
needed for respiration in organisms
how does soil type affect an ecosystem
certain plants will grow in certain pH of soil (producers)
needs to be soft enough to allow plants to grow
define trophic level
a stage in a food chain that’s occupied by a particular group of organisms
define producer
an organism that produces organic molecules using sunlight energy (plants)
define consumer
an organism that eats other organisms
draw a simple food chain
oak tree -> caterpillar -> starling -> cat
define biomass
dry mass of living material
producers store energy as biomass
Explain why biomass decreases at each level in a food chain
Energy is lost from an organism because…
- not all of an organism may be eaten,
- parts of an organism may be indigestible,
- some energy is transferred to the environment through metabolic heat,
- some energy is lost through excretion
give some examples of how human activities have improved ecosystems and the transfer of biomass
Herbicides - kill weeds that compete with agricultural crops for energy, grow faster, increasing productivity
Fungicides - kill fungal infections that damage agricultural crops
Insecticides - kill insect pests that eat and damage crops, less biomass is lost
Fertilisers - provide crops with minerals, increases efficiency of energy conversion
Rearing livestock involves controlling the conditions so more energy is used for growth, more biomass produced.
define decomposer
organisms that consume organic material (roots, bones)
define detritivores
an animal which feeds on dead organic material
define saprotroth
an organism that feeds on decaying organic matter
what do pyramids of biomass show
the total dry mass of all organism at each trophic level at a given time
The area of the bar is proportional to the dry mass of all the organisms at that trophic level
how could measure the amount of biomass in a material
Easiest way is to measure mass of fresh material
Water content in organisms must be removed
Organism heated in an oven at 80ºC until all the water has evaporated
Dry organism weighed to measure mass in grams
The figure is multiplied by the number of organisms present in a given area
what is the role of photosynthesis in the carbon cycle
carbon is absorbed by plants when they carry out photosynthesis
it becomes carbon compounds in plant tissues
this is passed onto primary consumers when they eat plants and then onto secondary and tertiary consumers
what is the role of decomposition in the carbon cycle
decomposers secrete enzymes which break down the carbon compounds in dead organic material
they then absorb the products of digestion for use in respiration
what is the role of respiration in the carbon cycle
carbon is returned to the air as all living organisms carry out respiration which produces carbon dioxide
what is the role of combustion in the carbon cycle
if dead organic matter ends up in places where there aren’t any decomposers (oceans/bogs), its carbon compounds can be turned into fossil fuels over millions of years
the carbon is released when they’re burnt
what is the role of volcanoes in the carbon cycle
rocks can be formed from dead organic matter (coal, limestone and chalk)
carbon can be returned to the atmosphere by the rocks being drawn deep into the Earth’s crust by the movement of tectonic plates
they undergo chemical changes and release carbon dioxide which is returned to the atmosphere by volcanoes
what is the role of weathering in the carbon cycle
the carbon-compound rocks can become land which is weathered
the rain can do this as it’s slightly acidic or physically by plant roots and animals
chemical weathering causes mineral ions and bicarbonate ions to be released from the rock into solution and enter ground water from where they’re transported into rivers and oceans
they combine with carbon-containing compounds like limestone
what is the role of oceans in the carbon cycle
carbon dioxide can directly dissolve into the oceans and be transported deep underwater by currents
carbon dioxide can remain in these slow moving currents for hundreds of years before returning to the surface and being released back into the atmosphere
define succession
the process by which an ecosystem changes over time
what’s the difference between primary and secondary succession
primary succession happens on land that’s been newly formed or exposed. there’s no soil or organic material
secondary succession happens on land that’s been cleared of all the plants but soil remains
what are pioneer species
the first species to colonise the area
specialised to cope with harsh environments
(seeds and spores are blown in by the wind and begin to grow)
describe the process of primary succession
1) Seeds and spores are blown in by the wind and begin to grow (pioneer species).
2) The abiotic conditions are harsh (no soil to retain water) but the pioneer species change the abiotic conditions - they die and microorganisms decompose the organic material and form soil.
3) Conditions are now less hostile and new organisms move in and grow. They add more organic material when they die, the soil becomes richer in minerals.
4) Larger plants can then grow, making more habitats so animals can move in.
define climax community
the final stage of succession where the ecosystem is supporting the largest and most complex community of plants and animals it can
it’s in a steady state
define plagioclimax
where humans have prevented an ecosystem developing and further
(eg. deforestation)
what’s the difference between abundance and distribution
Abundance is the number of one species in a particular area.
Distribution is where a particular species is within the area you’re investigating.
draw a pyramid of numbers for this food chain:
grass -> rabbit -> fox -> fleas
the bottom level is the largest then it gets smaller for rabbits and smaller for foxes.
the top level is then large as well because it takes a lot of fleas to consume one fox
(the pyramid of biomass however, would look like a normal pyramid)
what do pyramids of energy show
what are the units used
Pyramids of energy show the amount of energy available to the next trophic level.
Energy is measured in kilojoules per square metre per year, so seasonal anomalies will not show.
define ecological efficiency
The efficiency with which biomass or energy is transferred from one trophic level to the next
define gross production (in terms of food chains)
Total solar energy that plants convert to organic matter/absorbed or energy taken in
define net production (in terms of food chains)
Energy available to the next trophic level
why does the majority of the available energy to organisms not get taken in
Plants can’t use all light energy = wrong wavelength, some light is reflected, some light passes straight through leaf
Not all light can be used as it hits bark
Some parts of food e.g. roots/bones aren’t eaten (energy passes to decomposers)
some parts of food are indigestible so come out as waste/faeces (passes to decomposers)
define respiratory loss
energy lost to the environment when organisms use energy produced from respiration for movement or body heat
what equations can you use for net production and gross production
Net production = gross production – respiratory losses
Gross production = energy available – energy not taken in
what equation can you use for the efficiency of energy transfer between trophic levels in a food chain
% efficiency of energy transfer or ecological efficiency = (net productivity of trophic level / net productivity of previous trophic level) X100
how do calculate the efficiency of biomass transfer
first calculate the biomass consumed:
biomass consumed = mass (per m^2) x area of land
then:
% efficiency of energy transfer or ecological efficiency = (net productivity of trophic level / net productivity of previous trophic level) X100
what happens after primary succession in order to create a climax community
- At each stage, plants/animals better adapted out compete those already there, becoming the dominant species
- Ecosystem becomes more complex
- Creates more habitats, increases species diversity
- Eventually a climax community is reached – it won’t change much after this
define deflected succession
When succession is prevented by human activity, but the plagioclimax that develops is different to the normal course of the natural environment.
why is random sampling done
Ensures the sample isn’t biased
Ensures any variation observed in the sample isn’t just due to chance
write a method of how you can take a random sample on a field
Mark out a grid on the grass using 2 tape measures laid at right angles
Use random numbers to determine the x and y coordinates
Take a sample at each coordinated pairs
OR
Divide the field into a grid
Use a random number and letter generator to select the coordinates
Take samples at the coordinates
what are the differences between line, belt and interrupted transects
Line transect – species that touch the tape measure are recorded
Belt transect – using a quadrat, they are placed next to each other
Interrupted transects – measurements are taken at intervals, e.g. by placing a point quadrat at right angles to the direction of the transect e.g. every 2m
how do frame quadrats work
- placed on the ground at random points within the area you’re investigating
- the number of individuals of each species is recorded in each quadrat
- the percentage cover can also be measured by counting how much of the quadrat is covered by the species (count a square if it’s more than half covered)
how do point quadrats work
- this is a horizontal bar on 2 legs with a series of holes at set intervals along its length
- place on the ground at random points
- pins are dropped through the holes and every plants the pin touches is recorded
- the number of individuals if each species is recorded in each quadrat
- percentage cover can be calculated by counting the number of times a pin has touched a species and dividing by the total number of pins dropped
why does the abundance of a species change daily
Immigration
Emigration
Births
Deaths
how can you estimate the number of organisms in a population
Estimated number in population = number of individuals in sample / area of sample
what is the capture-mark-release-recapture technique
A sample of animals is captured, counted and marked in some way.
They are then released and allowed to remix with the population.
A second sample is taken later.
The population can be estimated from the proportion of marked animals in the second sample.
what are the limitations of the capture-mark-release-recapture technique
- the population always changes (could be a mass migration between taking the samples) and you’re assuming there are no deaths or births
- not all organisms could have an equal chance of being captured (mother’s and their young will be more timid)
- marks could be lost or could make the animal more noticeable to predators
draw the carbon cycle
look it up
draw the nitrogen cycle
look it up
what is the role of nitrogen fixation in the nitrogen cycle
what are the bacteria involved
Nitrogen fixation is when nitrogen gas in the atmosphere is converted to ammonia by bacteria such as Rhizobium and Azotobacter. The ammonia can be used by plants.
Rhizobium are found inside root nodules of leguminous plants. They form a multualisitic relationship with the plants (provide the plant with nitrogen compounds and the plant provides them with carbohydrates).
Azotobacter are found living in the soil.
what is the role of ammonification in the nitrogen cycle
Ammonification is when nitrogen compounds from dead organisms are turned into ammonia by decomposers, which goes on to form ammonium ions. Animal waste also contains nitrogen compounds - these are also turned into ammonia by decomposers and go on to form ammonium ions.
what is the role of nitrification in the nitrogen cycle
name the bacteria involved
nitrification is when ammonium ions in the soil are changed into nitrogen compounds that can be used by plants (nitrates)
first nitrifying bacteria called Nitrosomonas change ammonium ions into nitrites
then other nitrifying bacteria called Nitrobacter change nitrites into nitrates
what is the role of denitrification in the nitrogen cycle
denitrifcation is when nitrates in the soil are converted into nitrogen gas by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas
this happens under anaerobic conditions (no oxygen), eg. in waterlogged soils
Other than nitrogen fixation, how can nitrogen enter an ecosystem
Lightning
Haber process - making artificial fertilisers
what are the bacteria responsible for these processes in the nitrogen cycle:
a) Nitrogen fixation
b) Ammonification
c) Nitrification
d) Denitrification
Nitrogen fixation - Rhizobium and Azotobacter
Ammonification - Decomposers
Nitrification - Nitrosomonas and Nitrobacter
Denitrification - Denitrifying bacteria
