ecosystems, populations and sustainability Flashcards
2 types of decomposer
bacteria and fungi
what do decomposers do?
feed on/break down dead plant and animal matter
detritivores example and what to they do?
e.g. woodlice, earthworms
speedy up decay process by breaking up dead matter onto smaller fragments
increase surface area for digestion
what is saprotrophic nutrition?
obtaining energy form dead organic material
used by fungi
thread-like hyphae secrete enzymes extracellularly, digest dead material and reabsorb soluble products e.g. glucose, amino acids
why does decomposition result in CO2 being released?
glucose released form digestion is respired and this process releases CO2 and water into the atmosphere
what are myrcorrhizae?
relationship w/ plants?
fungal networks underground
form a symbiosis with plant roots
fungi obtain sucrose from plants
plants obtain more magnesium ions and phosphates from fungi
why is nitrogen so important for living organisms?
required to make nucleic acids (DNA/RNA) and amino acids (proteins)
why can nitrogen not be directly absorbed by living organisms?
very difficult to break the triple bond
must be combined with H atoms and O atoms, which increases the ability of nitrogen-containing molecules to be absorbed
processes in the nitrogen cycle
nitrogen fixation
ammonification
nitrification
denitrification
nitrogen fixation description
anaerobic process
reduction reaction
nitrogen-fixing bacteria ude nitrogenase enzyme
N2 + 3H2 -> 2NH3
16ATP -> 16ADP +Pi
nitrogen fixation bacteria involved
azotobacter (free in soil)
rhizobium (live in root nodules of legumes)
ammonification description
decomposers break down dead plant or animal matter and/or their products of egestion/excretion
egested products= rich in cellulose (B glucose, respired), proteins digested into amino acids; excess amino acids converted to urea, which bacteria use to respire
ammonification bacteria involved
saprotrophic micoroorganisms e.g. fungi, bacteria
nitrification description
aerobic process
oxidation reactions
in well-drained soil
1. ammonium ions-> nitrites
2. nitrites ->nitrates
nitrification bacteria involved
nitrosomonas
nitrobacter
both free in the soil
denitrification description
anaerobic process
occurs in waterlogged soils
reduction reaction
nitrates are converted back into nitrogen gas
NO3- ->N2
denitrification bacteria involved
pseudomonas
denitrificans (use nitrates for respiration)
nitrites symbol
NO2 -
nitrates symbol
NO3 -
nitrogen gas symbol
N2
ammonium symbol
NH4 +
ammonia symbol
NH3
purposes of leghaemoglobin?
similar structure to haemoglobin
found in root nodules
plats produce it to absorb oxygen (removes excess O2 so nitrogenase enzymes can have anaerobic conditions to increase efficiency of enzyme action)
this O2 is transported to mitochondria
what does nitrogen reductase do?
denitrifying enzyme
returns N2 gas back to the atmosphere
found in pseudomonas denitrificans
oxidation vs reduction
oxidation= loss of electrons/hydrogen
reduction= gain of electrons/hydrogen
besides nitrogen fixation, how else is nitrogen gas converted to ammonium?
Haber Process
fertilisers
differences between carbon and nitrogen cycle?
N: decomposers produce ammonium ions
C: decomposers produce CO2
denitrifying bacteria produce N2 (gas) from nitrates
N2 gas reacts with lightning or with N-fixing bacteria whereas CO2 can react directly in plants
similarities between carbon and nitrogen cycle
both involve decomposers, micro-organisms e.g. saprotrophs
both involve micro-organisms returning inorganic gas to the atmosphere
both involve death, digestion and excretion so both release either C or N - containing compounds
processes in carbon cycle
decomposition
respiration
photosynthesis
death
excretion/egestion
combustion
fossilisation
feeding
stores in carbon cycle
producers
consumers
decomposers
fossil fuels
atmospheric CO2
describe the part played by soil bacteria in making the nitrogen in compounds in dead plants available to living plants
saprotrophic micro-organisms such as bacteria and fungi break down the seeds to produce ammonium (decomposition/ammonification)
nitrosomonas and nitrobacter then convert this into nitrates which can be taken up by plants
reasons for less growth in areas w more plants
interspecific competition for nitrates
compounds classified as organic nitrogen
amino acids
protein
DNA
ATP
suggest the advantage to cattle farmers of encouraging the growth of clover in a grassland
contain bacteria which can fix nitrogen
clover decays/dies and adds nitrogen compounds to the soil
no/less fertiliser needed
succession definition
the directional change in the composition of species in a community that occupy a given area through time
pioneer community definition
a species adapted to survive harsh or inhospitable conditions. they stabilise the environment and lead to soil development e.g. lichens and fungi
climax community definition
a final, stable community
stable state
very little change over time
few dominant plant/animal species
secondary succession description
faster than primary succession as minerals are already available in the soil
occurs on land that has been cleared of all plants and animals but soil remains e.g. after flooding, forest fire e.t.c.
primary succession steps description
major disruption to ecosystem e.g. volcanic eruption, asteroid leaves bare rock without soil
lichens establish pioneer community, causing erosion of rock and providing dead material, which is decomposed and produces soil (humus)
shrubs and small plants e.g. ferns and mosses grow, which replace the pioneer community
plants establish themselves, reproduce, disperse seeds, die and decompose, adding minerals and water to soil
soil can support larger plant species, which outcompete smaller plants
continues until climax community forms
deflected succession description
when human activities halt succession from occurring e.g. agriculture (cattle farming, mowing, sustainable timber production)
STOPS climax community
plagioclimax definition
final community in a deflected succession ecosystem
what is the name of the stages in succession
seral stages
what causes succession?
changes in the community of organisms causes changes in the physical environment that allow another community to become established and replace the former community
therefore new community outcompetes former community: occurs in a number of seral stages: at each of these, key species can be identified that are responsible for changing the abiotic factors, particularly relating to soil (edaphic)
where are the pioneer species in sand dunes
why?
on the beach
they can tolerate harsh conditions e.g. high winds, high salt, high water
description of beach in sand dunes
bare sand
hostile environment: very salty so has low water potential. very windy. no organic matter
very low species diversity
description of mini dunes in sand dunes
embryo dunes
wind = blown sand builds up around base of pioneer plants
dunes increase in height as the plants grow
supports primitive species like MARRAM GRASS
young yellow dunes description in sand dunes
increased stability and more minerals therefore more marram grass growth
marram grass stabilises sand, some dies/decomposes, adding further organic matter to the sand
old grey dunes description in sand dunes
support intermediate plant species, these are able to outcompete pioneer species and increase species diversity
increased species diversity as you move further away from the sea
why do the dunes get darker as you go away from the sea?
soil depth and quality (mineral content) increases
larger root networks add to dark colour
marram grass is a xerophyte. what adaptations does it have? how does this help it to survive?
thick waxy cuticle reduces water loss by transpiration
rolled leaves (small) trap moist/humid air & decrease SA:vol ratio for transpiration
hairs on the lower surface reduce air movement to limit water loss
stomata are sunken so moisture trapped close to them to reduce water potential gradient
how would you measure change across a sand dune system?
an interrupted belt transect
does not lay flat along the ground
quadrats placed at regular intervals between 2 tape measures and number of organisms of each species is recorded
systematic sampling
take multiple reading at each interval and calculate mean
ensures sample is as representative as possible
what is a kite diagram?
allow frequencies of different species to be recorded along the length of a transect
the wider the kite, the greater the proportion of that species
advantage for pioneer species?
no competition
why can’t we predict the route which succession is going to take?
randomness
unpredictable variability (weather conditions e.t.c.)
what is the main way we can tell if an area is in a later stage of succession?
it has high biodiversity
lots of niches for species and many communities
what level of disturbance results in the greatest developmental change
mid-level disturbance: creates own habitat at its own stage of succession w/ its own unique niches
higher biodiversity and therefore a more stable and healthy ecosystem
why do people burn forests regularly?
undergo succession, creating an area of high biodiversity with a mosaic of habitats and communities
explain the role of pioneer plants in succession on a bare rock or sand dune
allows soil to hold more water and increase nitrogen content
reduces soil erosion
they stabilise the ecosystem by developing soil and increasing its quality so grasses can grow
how can deflected succession be caused
grazing of cattle
burning
herbicide use
explain how biomass changes during primary succession
plans in seral stages are larger
climax community= woody trees/shrubs appear
suggest how grazing by sheep could prevent a woodland climax community from developing
cause deflected succession so results in plagioclimax
outline the advantages of using a scale e.g. ACFOR scale
can be used with any species irrespective of size
quick to assess
doesn’t require distinguishing between individuals
outline the disadvantages of using a scale e.g. ACFOR scale
subjective. not objective
dominant species may be overestimated
outline 2 changes which occur between mid and late succession
topsoil becomes deeper and thicker
soil becomes richer in minerals
root networks become larger and more well-established
plant species become larger
conservation definition
maintaining biodiversity by actively managing ecosystems]
dynamic process involving human action
preservation definition
protecting an ecosystem by restricting all human access and use so it remains untouched
economic reasons why conservation is important
sources of raw materials for industries e.g. timber products from natural and plantation forests for the construction & paper industries
employment for people in transport, marketing & retailing; ecotourism also provides employment for many people in places of high biodiversity
sources of natural income from exporting biological resources e.g. timber, fish, paper products: the UK is a net importer of timber & fish, but exports of fish and shellfish are worth over £1bn
social reasons why conservation is important
human communities in rural areas w/ little industry or commerce gain stability from the employment provided by fishing or forestry
areas set aside for forestry provide spaces for recreation: the Forestry Commission & private forestry owners manage their forests as an amenity for people to enjoy the visual appeal of forested areas, the opportunities to take exercise and observe wildlife
ethical reasons why conservation is important
the duty we have to conserve resources for the livelihoods and wellbeing of future generations
the support of indigenous people across the world who maintain their traditional ways of living relying on certain biological resources e..g Inuit people in the Arctic rely on seals and whales & Amazonian communities depend on foods harvested from the rainforest
3 reasons why tropical rainforest have been destroyed
timber products/timber as fuel
clearance for agriculture
urban growth and development
describe the importance of tropical rainforests an why their disappearance is concerning
carbon sinks: remove CO2 from atmosphere
release stored carbon when burnt and stop photosynthesising, decreasing oxygen production
deforestation disrupts water cycle, by decreasing transpiration
more soil erosion
soils are nutrient deficient and cannot sustain agriculture
decreased gene pool
new medicines only in rainforests may be lost
conserve for later generations
extinction of species
high species diversity in small area of rainforest
how can international measures be taken to try and halt decline of tropical rainforests
ITTS
ecotourism
educaiton
reserves
rio CBD
IUCN/REDD
debt reduction
what is a sustainable resource
a renewable resource that is being economically exploited in such a way that it does not diminish/run out
uses of timber
in construction
as a fuel
in paper manufacturing
advantages of sustainable timber production
ecosystem not destroyed
biodiversity maintained
aesthetic and amenity value retained
long term financial benefit available from timber
what is sustainable timber harvesting
removing timber from a forest or woodland in a manner that allows similar amounts to be removed year after year
maintains the forest ecosystem, allowing all the different habitats and species to survive
how long do coppiced trees live
hundreds of years
describe the process of coppicing
tree that has been previously coppiced is cut at an angle so water runs off (less chance of fungal infection) and wood is harvested
in the following year lots of new stems are produced
after 9 years a few stems have produced significant growth
wood is harvested gain
wood is divided into 9 areas; each year, one area is coppiced (some trees grown to maturity= standard)
what does coppicing allow for
allows wood to be taken each year
most deciduous trees do not die when they are cut down and regrow form the base
examples of trees which are coppiced
sweet chestnut
ash
lime
hazel
issues with coppicing
labour intensive
small scale only
doesn’t work with coniferous trees
new growth of coppice trees= several stems, narrow (limited use BUT okay for paper, fencing or burning to generate electricity)
coppicing vs pollarding
coppicing- cutting trees to ground level: encourages more growth
pollarding- cutting higher up the trunk, useful if deer population is high
how does coppicing increase biodiversity
open glades promote wildflowers: different habitats created (trees never grow tall enough to block out light so succession halted)
small scale
management technique
size of timber
use of timber
habitat destruction
biodiversity
soil erosion
planting new trees
coppicing
smaller
paper, fencing, electricity
less
increases
none
no
large scale
management technique
size of timber
use of timber
habitat destruction
biodiversity
soil erosion
planting new trees
felling
larger
construction industry
more
decreases
yes
yes
clear felling is on what scale?
large
issues with clear felling
destroys habitats
reduces soil mineral levels
increases soil erosion
increase flood risk
what is selective felling
cutting only trees which are commercially viable/ diseased/unwanted trees
where is selective felling important and what is the rotation time
on slopes (trees prevent soil erosion)
long rotation time of 100 years to ensure regeneration
what does selective felling maintain
nutrients in forest soil (role in C and N cycles)
selective felling issue
difficult to carry out with large machinery
what is strip felling
small patches or strips of forest are cleared completely leaving other patches untouched to cut many years later
what does strip felling avoid
loss of species and soil erosion avoided as large areas not felled at the same time
making the most of each tree: if each tree supplies more wood, less trees are needed
what are the benefits of this?
control pests and pathogens
uses every part of felled trees e.g. small branches chipped
if management is stopped, what would woodlands go through
a process of natural succession (reach a climax community in which biodiversity would be much lower than in a managed woodland)
outline the use of coppice w/ standards in sustainable woodland managememt
trees cut to sloping stump close to ground
new shoots form
harvest periodically in same way
rotational coppicing to maximise age and size range of trees/maximise habitats
increase light intensity for seed germination/seedling/growth/creates varied abiotic conditions
increases habitats and biodiversity
provides continuous source of products/fencing/poles/furniture/charcoal
standards provide larger planks/more valuable timber
what are the marine stewardship council principles for sustainable management of fisheries
fishing must take place at a level which allows it to continue indefinitely
fishing must be managed to maintain structure, productivity and diversity of the ecosystem
a fishery must adapt to changes in circumstances and comply with local and international regulations
methods of fishing control
set up exclusion zones (no catch zones) fish migrate into and out of these areas (spawning/nursery grounds)
beginning fishing at certain times of year (e.g. during spawning, so allows fish numbers to recover)
rules of type of fishing gear e.g. larger mesh size to allow younger fish to escape, allowing them to reach breeding age/ limit number of boats in area
quotas: certain mass or number of fish per fisherman each year and inspect
restocking sea with young fish
international agreements
fish farms (aquaculture) rather than wild populations
how are fish stocks increased
brith of fish
growth of fish
how are fish stocks decreased
death of fish by natural means e.g. age, disease
humans catching fish
what is ICES
an independent intergovernmental scientific body providing advice on fisheries in NE Atlantic to National Governments
how is overfishing prevented
limit areas where fishing can take place
decrease total net size
increase net mesh size
set minimum landing sizes e.g. min. size of fish that can eb brought into port
reduce/stop subsidies for increasing size of fleet
suggest 3 reasons why quotas are not always effective in preserving fish stocks
inaccurate estimate of size of fish populations
fish caught above quota have to be returned to sea (but are unlikely to survive)
quotas exceeded illegally
small fish may be caught
fish not caught may be eaten by predators
describe the LT ecological effects of overfishing
disruption to food chains/webs
reduced productivity of ecosystem
loss of biodiversity
loss of nutrients from ecosystem
what assumptions foes the capture/recapture technique make?
no immigration/emigration
tagging has no effect on predation/likelihood of capture/survivorship
what is peat
consists of the remains of fallen trees/branches/leaves/plants and other carbon matters that have built up in waterlogged conditions over 1000s of years
no/slow decomposition (carbon stays in solid state)
what happens to peat when drainage ditches are dug?
water that was previously stored in the peat starts to flow out of the ditch
sunlight enters the forest so more temps
oxygen enters peat so it begins to decompose
carbon converted to CO2, which moves away
large scale= issue
water table lowers so peat dome subsides
fire accelerates smokinh
how many billions of tonnes of carbon is stored by the UKs peat bogs
3
why should bogs be conserved
provide habitats e.g. for sphagnum moss, bog cotton, lichens, sundew
abundance of insects e.g. butterflies attracted by a wide variety of plants or damselflies and dragonflies
habitat for birds e.g. snipe, skylark
frogs, lizards, hares foes e.t.c. live at bogs
store CO2
archaeologists use to analyse past
part of heritage
flood management
how much water can sphagnum moss store?
20 times its own weight
when does peat form
when plant material is inhibited from fully decaying by acidic and anaerobic conditions
normally occurs ion wet ares so peat is mainly composed of wetland vegetation e.g. mosses
what is a bog
a wetland area which is waterlogged only by direct rainfall
why is peat being destroyed
peat extraction to use as fuel
afforestation of area
agricultural intensification
drainage ditches
garden compost
describe conservation of lowland bogs
organisations like wildlife trusts and rspb carry out conservation work
ensures that peat and vegetation of bog surface is undisturbed and as wet as possible
ditch blocking to raise water table
removal of seedling trees
controlled grazing
why has human population not changed much throughout history
due to limiting factors preventing increase e.g. food availability, predation, disease, climate
what recent developments led to exponential increase in global human population
industrial revolution, scientific revolution, public health revolution and development of agriculture
what does exponential increase mean
as time doubles, population more than doubles
population definition
members of the same species in the same place at the same time able to interbreed w each other
population size definition
number of individuals in a population
population density definition
number of individuals per unit area
limiting factor definition
a factor whose magnitude slows down the rate of a natural process
abiotic factor definition
non living
e.g. soil pH, moisture, temperature, light intensity
biotic factor definition
living
e.g. predation, competition, disease
interspecific competition definition
competition between organisms of different species
intraspecific competition definition
competition between organisms of same species
what is a growth curve
if the growth of a population over time is plotted on a graph, regardless of the organism, most natural populations will show the same characteristics
stages of a population growth curve
lag phase
log phase
stationary phase
death phase
describe the lag phase of a population growth curve
(period of slow growth)
acclimatising to habitat (i.e. adjusting to nutrients, genes switched on to make appropriate enzymes)
only a few individuals, so low rate of reproduction
birth rate greater than death rate but growth in population size is slow
describe the log phase of a population growth curve (population increases rapidly)
can only be maintained if resources are plentiful and conditions are good
numbers double each generation (=max rate of reproduction every 20 mins)
birth rate much greater than death rate (maximum rate of reporduction)
describe the stationary phase of the population growth curve (population levels out at carrying capacity)
birth rate equal to death rate
population remains stable/ fluctuates slightly
fluctuations are due to variations in environment (limited/changing food supply/outbreaks of disease i.e. abiotic and biotic factors which decrease BR or increase DR)
what is carrying capacity
the maximum population size that can be maintained over a period of time in a particular habitat with a particular set of conditions
further growth stopped by environmental resistance e.g. abiotic and biotic factors which reduce BR or increase DR
describe the death/decline phase of a population growth curve (population decreases in size)
death rate greater than birth rate
lack of resources
buildup of toxic waste
not usually shown in natural populations
what is a niche
the role of each species in an ecosystem
role refers to position in food chain and how it interacts with the environment and other species
why is a food web more useful than a food chain
a food web is more realistic than a food chain: each trophic level usually consists of more than one species of organisms and most consumers will eat more than one type of organism
why is a pyramid of biomass more useful than a pyramid of numbers
pyramid of numbers does not reflect the varying sizes of organisms at each trophic level
a pyramid of biomass provides a more accurate picture of how much biomass exists at each trophic level
GPP definition
the rate at which plants convert light energy into chemical energy through photosynthesis
8 ways that farmers can increase NPP
plant crops earlier to increase length of growing season
use light banks to grow plants
irrigate crops
introduce drought-resistant strains
grow plants in glasshouses to provide a warmer temperature
pesticide use
crop rotation
selective breeding to resist fungal infections
use of herbicides
4 ways farmers can improve secondary productivity
harvesting animals just before adulthood
selective breeding to increase animal growth rate/ egg production/ milk production
treatment of animals with antibiotics
zero grazing for pigs/cattle
describe how selective breeding and GM can increase primary and secondary productivity
by producing consumers or primary producers that are more efficient at increasing their biomass
describe how saprotrophs feed
secrete extracellular enzymes onto dead and waste material
enzymes digest the material into small molecules, which are then reabsorbed
explain why all stages of succession are visible on a sand dune
the sea deposits sand on the beach
the sand closets to the sea is deposited more recently than the sand further away
this means the sand nearest to the sea is at the start of succession whereas the sand further away may have already reached its climax community
describe what is meant by the competitive exlcusion principle
2 species have exactly the same niche, so one is outcompeted by the other and dies out or becomes extinct in the habitat
describe how the terai region has made resource use more sustainable
created forest corridors
counteracted poaches and illegal felling
introduced biogas plants and wood-efficient stoves
constructed waterholes
monitored endangered species
eradicated invasive species
describe how the Maasai mara region has made resource use more sustainable
created conservancies that allow limited grazing and tourism opportunities to co-exist
state the similarities between the strategies adopted in the terai region and the Maasai mara
both strategies acknowledge the importance of local people and work with them
both have conservation with developmental aspects
explain why both the terai and Maasai mara projects have involved the local community
both area provide homes to many local people and those people depend on the habitat for their existence
it makes sense to improve conditions for local people at the same time as conserving the habitat
it is important to involve local people so they do not act against the conservation aims
describe the positive and negative consequences in terai
forests provide local people with a sustainable source of fuel, animal feed, food, building materials, agricultural and household tools as well as medicines
tiger populations appear to be increasing
increasing tiger populations may tempt back poachers
describe the positive and negative consequences in Maasai mara
positive partnerships between conservancies and tourism organisations
sustainable farming and tourism opportunities for locals
landowners are forced to move their livestock out of the conservancies during the tourist seasoned can be forced to re-settle elsewhere
producer definition
organism that converts simple inorganic source of carbon into complex organic molecules
supply chemical energy to all other organisms either directly or indirectly
how to sample (different methods)
random sampling
systematic sampling
stratified sampling
opportunistic sampling
how to carry out random sampling
set out 10m x 10m Grid using tapes
use random number table to generate pairs of random no.s and then put bottom left corner of quadrat at co-ordinate
random sampling use
used to compare 2 or more areas
avoids bias
how to calculate population size of whole area from random sampling
mean number of individuals of a species in a quadrat/fraction of total habitat covered by 1 quadrat
systematic sampling use
to investigate changes along an environmental gradient
types of systematic sampling
line transect
belt transect
describe line transect
a line across a habitat from one end to another
sample at regular intervals and only count what touches the tape
describe belt transect
parallel tapes with a quadrat at regular intervals
can be continuous or interrupted
belt transect vs line transect
belt transect takes longer
belt= more data, more representative
continuous vs interrupted belt transect
continuous is higher number of quadrats so more data and more representative
stratified sampling use
to investigate a habitat which has distinct different areas
sample each area proportionally to its size as a percentage of whole habitat (STRATA=GROUPS)
what are opportunistic sample sites based on
prior knowledge e.g. safe areas w particular species
(may not be representative so weakest form of sampling)
what are cyclic changes in an ecosystem w examples
changes that repeat in a rhythm
e.g. movement of the tide, changes in day length, fluctuations in predator-prey species
what are directional changes in an ecosystem w examples
these changes tend to go in one direction ie a particular variable continues to increase/decrease
tend to last longer than the lifetime of an organism in an ecosystem
e.g. deposition of silt in an estuary , deposition of sand forming a dune, coastal erosion
what are unpredictable/erratic changes in an ecosystem w examples
no rhythm or constant direction
e.g. effect of lightning, hurricanes, pollution
examples of how living organisms respond to changes in ecosystems
hibernation in cold months
changes in thickness or colour of coat
migration to warmer areas
loss off leaves to avoid water loss
dormancy of seeds until warmer months
flowering (delayed until pollinators are around)
step by step sand dune succession
bare ground colonised by pioneer species e.g. marram grass that can tolerate the dry, salty condiitons
marram grass stabilises the sand due to its dense roots
as the marram grass decays it makes the sand less hostile, adding humus and improving water retention
this allows other plants to grow e.g. grasses, ragwort, restharrow
as plants build up and then decay, soil depth and quality improve further allowing taller plants to establish- firstly small shrubs and then trees
this greater variety increases biodiversity encouraging the presence of insects and birds
eventually a stable woodland may develop
damage to dunes by rising sea levels, storms or trampling may reverse succession. these are deflecting factors.
biomass definition
mass of living material (including organic and inorganic components)
can be used to determine energy content
is biomass expressed as wet or dry mass
why?
dry mass bc gives a better representation of energy content (but it is destructive)
this is bc plant wet matter varies considerably due to fluctuations in water uptake and transpiration
how to get dry mass of an organism
put in oven at 80C until constant mass
how to calculate biomass of a population (so can measure change over time)
measure dry mass of a small representative sample of population and scale up for the whole population
what is biomass measured in
gm^-2 for land organisms
gm^-3 for aquatic organisms
how to calculate efficiency of transfer between trophic levels
biomass of higher trophic level /
biomass of lower trophic level x100
GPP definition
rate at which plants convert light energy into chemical energy through photosynthesis
total production of organic material in a given time and area
why is energy los between sun and producers
some light misses leaves/plant (e.g. bark cannot photosynthesise)
some light reflected
some light transmitted and not trapped (passes straight through leaf and doesn’t hit chlorophyll molecule)
only certain wavelengths can be absorbed:blue & red (plant does not possess enough pigments to absorb all wavelengths)
energy losses occur in p/s reactions
there may be other factors which limit the rate of p/s (e.g. temp)
what % of solar energy do producers convert into chemical energy and hence biomass
0.5-3%
where is GPP higher
at equator than at poles
why is GPP higher at equator than at poles
higher light intensity
higher temp so higher enzyme activity
faster rate of p/s
more glucose made so more organic material produced in a given time/area
NPP definition
energy which remains as chemical energy after the plants have supplied their own needs in respiration
energy released in respiration is used to drive metabolic reactions
what % of energy generated in p/s do producers use for other processes eg. respiration
20-50%
equation liking NPP and GPP
GPP=NPP +R
NPP=GPP-R
biomass losses between producers and primary consumers
not all parts of the plant are eaten e.g. roots/woody tissue
large proportion of the parts eaten are undigestable e.g. cellulose and lignin
what % of energy is transferred between producers and primary consumers
5-10%
biomass losses between primary consumers and secondary consumers
greater proportion of organism is digestible (but cannot digest all parts e.g. bones)
primary consumers use some biomass in respiration for movement
primary consumer loses heat energy to surroundings
primary consumer loses biomass in urine/faeces (egestion)
what % of energy is transferred between primary and secondary consumers
10-20%
what is production by heterotrophs called
secondary production
positive of using pyramid of numbers
easy to collect data and to draw
negatives of using pyramid of numbers
range of numbers may be v big e.g. 500,000 grass plants may only support a single top carnivore so drawing may be tricky to do scale
doesn’t account for size of organism
pyramid of biomass positives
eliminates the inversion and scale problems of a pyramid of numbers
issues w a pyramid of biomass
destructive bc use dry mass
doesn’t take into account seosnal changes
how to measure energy content
dry sample and burn in calorimeter
calculate energy released in kJkg^-2yr^-1
multiply by biomass at each trophic level
advantages of pyramid of energy
comapres productivity bc a itme factor is incorporated
no inverted pyramids obtained
how does LI limit productivity
lower LDR so lower rate of p/s
slower production of biomass
how to limit effect of LI on productivity
plant crops earlier and use light banks
how does water limit productivity
decreased photolysis so lower rate of p/s
slower production of biomass
how to limit effect of water on productivity
irrigation
GM drought resistant strains
how does temp limit productivity
decreased enzyme activity of rubisco
decreased rate of p/s
decreased production of biomass
how to limit effect of temp on productivity
plant crops earlier
grow plants in a glasshouse
how do mineral ions limit productivity
decreased growth e.g. magnesium and nitrates
decrease chlorophyll and amino acids
slower production of biomass
how to limit effect of mineral ions on productivity
crop rotation
nitrogen-fixing crops e.g. legumes like clover
selective breeding crops t respond to high levels of fertiliser
how do pests limit productivity
eat and damage crops to decrease biomass
how to limit effect of pests on productivity
spray w pesticides
selectively breed to be pest-resistant
GM to be pest-resistant
how do fungal diseases limit productivity
damage roots to decrease volume of water absorbed
damage xylem so decrease water transport
damage foliage so decrease leaf area for p/s
damage phloem so decrease translocation
damage flowers/fruit so decrease reproduction and biomass
how to limit effect of fungal diseases on productivity
spray w fungicides
selectively breed resistances
GM to be resistant
how does competition from weeds limit productivity
decreased p/s
decreased production of biomass
how to limit effect of competition from weeds on productivity
use herbicides to kill weeds
how to improve secondary productivity
harvest animal before adulthood (young invest greater % of their energy into growth)
zero grazing max. energy allocated to growth
treatment w antibiotics avoids unnecessary energy losses during disease
limit space for movement, food supply, keep temp constant (warm means less energy lost to surroundings as heat)
select and produce breeds w higher growth rates incl. egg/milk production
how to measure energy content of a sample
measure biomass and dry in oven at 80C until constant mass
burn in O2 in calorimeter and measure temperature increase
calculate energy content using equation
why are there usually no more than 4 or 5 trophic levels in a food chain
proportion of energy transferred at each trophic level is small <20%
energy losses e.g. heat loss from resp/movement & faeces limit % energy transfer
after 4/5 tropical levels, insufficient energy to support large enough breeding population
similarities between carbon and nitrogen cycles
involve inorganic gases CO2 and N2 in atmosphere
involve these elements being returned to the atmosphere by microorganisms such as decomposers releasing CO2 and N2 released by dentrifying bacteria
involve elements being fixed to organic compounds e.g. C and N both form proteins/nucleic acids
compounds are incorporated into producers and consumers
animals obtain element N or C by feeding
decomposer m/o’s e.g. bacteria/fungi
involve decomposition of organic macromolecules and the release of inorganic molecules e.g. ammonia
differences between C and N cycles
C fixation provided by p/s but N fixation provided by N fixing bacteria
COI2 converted to glucose/sugars by plant, NH3 ions converted to amino acids/proteins in plants
fixed C is released into atoms by combustion/resp, N is released by denitrification
inorganic mols taken up differently by plants in each cycle: CO2 via stomata and NH3/NO3 via AT in roots
p/s only in C cycle
C cycle includes combustion of fossil fuels
N cycle involves nitrifying and N fixing bacteria
N cycle shows symbiotic mutualistic relationship between legumes and Rhizobia
aspects of ecological niche occupied by clovers in plant comminities
have N fixing bacteria in root nodules
clovers decay releasing NH3 into soil
symbiotic relationship
not dependent on taking N compounds from soil (provided by Rhizobia)
suggest factors that may prevent a plant species from colonising other habitats
pollution from vehicles
interspecific competiton
needs good drainage
difference in soil depth/type
cannot tolerate grazing/mowing
cannot tolerate disturbance
different nutrient levels
different light levels
agricultural activity
suggest 2 ways in which leg haemoglobin improves performance of nitrogenase enzyme
transports O2 for resp/to generate ATP in Rhizobium
removes excess O2 to decrease inhibition of enzyme
anaerobic conditions for N fixation
shape of curve for when a plant or animal starts a population in a new place
s shaped (sigmoid)
describe sigmoid curve when an animal or plant starts population in a new place
exponential growth in first part
followed by population regulation as number of plants or animals approaches carrying capacity and negative feedback takes over
fluctuates in vicinity of carrying capacity
SOMETIMES grows so rapidly it overshoots CC before -ve feedback can stop the increase. this depletes food so severely that the -ve feedback in the form of more deaths and fewer births quickly reduced it below CC
types of limiting factors preventing a population from increasing in size
density dependent factors
density independent factors
what is a density dependent factor
effects depend on the density of the population (larger effect on larger pop (regulatory effect))
e.g. factor that causes an increase in deaths when pop density increases
are density dependent factors usually abiotic or biotic
biotic
examples of density dependent factors
food (e.g. prey more difficult to find)
oxygen conc
CO2 conc (if plant)
territory/shelter
^^ all increase competition
predation (predators are more attracted to higher density prey pops bc easier to catch)
disease (spreads more easily at higher densities)
IN EXAM Q BE SPECIFIC TO FOOD CHAIN GIVEN
what is a density independent factor
factors with similar effects regardless of population density
e.g. a factor that causes deaths irrespective of the number in the population
are density independent factors usually biotic or abiotic
abiotic
examples of density independent factors
climate change
fire
volcano
2 types of species
k and r
(k- carrying capacity)
(r- growth rate of pop)
what is a k-strategist species
species whose population size is determined by the carrying capacity
limiting factors exert more and more significance as the pop size gets closer to CC, causing pop to level out
what is an r-strategist species
species whose population increases so quickly it exceeds the carrying capacity before limiting factors have an effect (boom)
once carrying capacity exceeded, lack of resources and toxins lead to death/decline (bust)
are all species k or r strategists
no: continuous spectrum
k and r species are the 2 ends of the spectrum: many species show characteristics of each
examples of species w part k and part r strategist characteristics
sea turtle
trees
examples of r-selected species
pioneer species
frogs
examples of k-selected species
elephant
human
tree
lifespan of r-selected species
short
lifespan of k-selected species
long
time to reproductive maturity: r selected species
short
time to reproductive maturity: k selected species
long
number of reproductive events: r selected species
many
number of reproductive events: k selected species
few
number of offspring: r selected species
many
number of offspring: k selected species
few
size of offspring: r selected species
small
size of offspring: k selected species
large
parental care: r selected species
none/little
parental care: k selected species
lots/significant
population growth rate: r selected species
fast
population growth rate: k selected species
slow
competitors: r selected species
poor
competitors: k selected species
good
population dynamics: r selected species
highly variable
population dynamics: k selected species
stable near carrying capacity
environment: r-selected species
unstable environment
low nitrogen content
low shade
environment: k-selected species
stable environment
high nitrogen content
low light intensity
where do predators often specialise on a single prey species
northern climates
e.g. Canadian lynx on snowshoe hares or Goshawks on ruffled grouse
describe interrelationship between predator and prey population sizes
when pred pop increases, more prey get eaten
prey pop decreases so less food for preds
less food so fewer preds survive and pop size reduces
fewer predators so less prey eaten so pop size increases
more prey so pred pop increases and cycle restarts
PREDATOR CURVE FOLLOWS PREY CURVE
why is no. of predators generally smaller
higher in food chain
why is there a delay in change of predator pop after prey pop changes
takes time for the BR to respond to changing conditions
why predator pop not competely depleted when prey pop drastically lower
found other food source
other factors involved in predator prey relationship
higher species diversity in ecosystem means more difficult to see predator prey relationships
predator eats several kinds of prey so can switch to another if 1st species pop declines
other limiting factors (correlation not always causation, competition for food, space, mates also play a role in pop dynamics)
what does removal of a strong competitor prey population by predators enable
weaker competitors to survive
reduces effect of competitive exclusion
ecosystem benefits after reduced effect of competitive exclusion
increased species diversity
increases stability
ability to adapt to env change
reintroduction of wolves to Yellowstone park increased biodiversity (conservation strategy)
what is a niche
species role in its ecosystem e.g. the feeding role in food chain (producer, parasite, predator), habitat, reproduction method, behaviour
do members of same pop have same or different niche
same
well adapted to niche e.g. nectar feeding birds have long thin beaks
describe infraspecific competition
between members of same species who share same niche
competition for food, water, territory, mates, light
comp slows growth and pop enters stationary phase
pop fluctuates around carrying capacity (stabilising effect on pop size)
describe interspecific competition
between individuals of different species when their niche overlaps
greater the overlap, greater the competition
can affect pop size and distribution in an ecosystem
example of interspecific competition: squirrels
Red squirrels= native species (nimble, light, put on less fat in winter, struggle to digest acorns before ripe)
Grey squirrels= introduces in 1800s (wider food range, twice as heavy, store more fat, can decimate crops of acorns before ripe and become viable food source for reds)
competitive exclusion principle definition
if 2 species have exactly the same niche, one always outcompetes the other which then dies out
OR
one species may be pushed into another niche (niche partitioning)
examples of competitive exclusion principle
paramecium (microscopes single celles Protozoan)
flour beetles
competitive exclusion principle Paramecium
grow P.aurelia and P.caudatum together and separately
when grown separately, P.aurelia has highest pop
when grown together, competition for food, P.aurelia obtains food more efficiently, P.caudatum less so and dies out in 20 days, P.aurelia pop increases and is eventually only remaining species, P.caudatum competitively excluded
competitive exclusion principle flour beetles
if Tribolium confuseum and Tribolium casteaneum grown together, one species will competitively exclude the other
small changes in temp determine which species will survive
>29C: T.casteaneum survives
<29C T.confusum survives
describe niche partitioning barnacles example
Chthalamus is able to live high up and low down the shore
Balanus can only survive low down and always outcompetes Chthalamus and eventually replaces it completely
this is bc Balanus grows faster, occupies the limited space more quickly, can grow over the other barnacles or under them to lift them off the rock
