Summary
Summary CCEA GCE Biology - Chapter 7 - Ecological energetics and nutrient cycling
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Mindmap on ecological energetics and nutrient cycling based on CCEA A2 1 biology.
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P = secondary productivity Energy lost as heat in respirationP = C - (R + U + F) Energy transfer bet ween animals or consumers
C = energy consumed Sun is more efficient than bet ween plants and
Maximising P (by using high R = respiration
energy foods), reducing R, F herbivores. More of an animal can be eaten and
F = faeces 0.5 - 1% digested, only a small proportion of the energy
and U leads to increases in U = urine 5-10% Primary 10-20% Secondary 10-20% Tertiary
Producers in any animal will be built up into organic
growth and profit. consumers consumers consumers
compounds in the next tropic level due to
excretory losses, uneaten structures or being
·
Energy budget - measures efficiency of Detritivores/
secondary productivity decomposers used in respiration or through death and entry
into the decomposer food chain. The energy
Energy lost as heat in respiration through trophic levels is energy flow. It's not a
There has been a lot of investment in increasing agricultural productivity. from detritivores and decomposers cycle as sun is continually providing energy.
Increasing primary productivity in plants - crop growth can be increased by removing or reducing the waiting
tabors affecting growth. Can be done artificially in glasshouses by providing extra light,heat and CO2, most ave Energy transfer bet ween consumers
grown outside and the most realistic way of increasing productivity through the use of fertiliser and reducing the Shows the link bet ween a producer, primary consumer, secondary
effect of pests. Can also be enhanced through appropriate spacing of crops in a field. Sowing seeds at the optimum consumer and tertiary consumer. Each stage is a trophic level, starting
density ensures that competition against adjacent crops is reduced but allows maximum coverage of land. Least efficient stage bet ween producers + primary consumers. Some with producers. Food chains aren't very accurate as most animals do not
Intensive farming of domestic livestock - by making energy conversion more efficient and restricting energy losses, plant materials can't be accessed eg. Plant roots and tree trunks, rely on a single food source. Food webs are patterns of interrelated 'food
more energy (meat products) will be available to humans. Includes the confinement of animals to very specific areas - which don't get eaten as it is very difficult to digest few species have chains'
can be cattle in a fenced-off section or pigs in an outhouse. Keeping cattle in a small section of a field also ensures the enzymes necessary to digest cellulose and lignin. Herbivores Helpful as they show path of energy flow but do not provide any
that less land is utilised at any one time and that manure from animals is more evenly spread over the land. typically only assimilate a small percentage of the plant material information concerning numbers, biomass or organisms ie. Qualitative
Keeping animals indoors in warm conditions - with warmth being provided by the animals themselves which reduces they eat with excretory lasses contributing to energy losses - relationships. Relative number, biomass or energy of the organisms
the energy required. High energy foods (vilage) and high protein foods increase productivity. Many ethical issues metabolic waste (urea) is excreted which represents energy that's involved can be represented through the display of ecological energetics.
occur > high stress levels, bone and joint damage (hooves didn't evolve for movement on concrete especially slats). not available to be transferred to the next tropic level. Much of the Pyramids of numbers represent the total number of organisms at each
Management issues > disease is likely to spread rapidly in close proximity. Antibiotic resistance has been affected organic content eaten by primary consumers is used din respiration tropic level in a food chain/web. Length of bars = number at each level.
by this. Reduced genetic diversity results thorough selective breeding of the productive and profitable varieties and to generate ATP. The energy 'lost' is lost as heat - a byproduct of the They don't take into account size of an organism. With very large
increased pollution from use of fossil fuels or general farmland waste. Energy efficiency and the human diet - respiratory process. Respiratory lasses are high in endothermic. numbers it's difficult to scale the bars accurately.
production of animal products is much less efficient than using crops. Much more energy is available to humans Maintenance of high and constant body temperature requires high Pyramids of biomass represent the biomass of organisms at a particular
through eating plant products. Each human who eats meat requires more land than a vegetarian. Productivity in metabolic activity and high levels of respiration and unavoidable tropic level in a food chain/web. Biomass can be measured as fresh mass/
animals (secondary productivity) - energy used in production of new tissue in animals is secondary productivity. heat loos. Plants enter the decomposer food chain when they die. dry mass. Fresh mass is more variable but more accurate dry mass
Crop farmers want to increase primary productivity (crop growth) but farmers of livestock are concerned with (drying organisms until content mass is achieved) is more accurate but
primary and secondary productivity. time consuming, organisms are killed. Only organisms present at any one
Energy transfer bet ween time are considered. Inverted pyramids for food webs are much less
producers and consumers common. Examples marine or aquatic pyramids of biomass as they don't
Essential component of all major macromolecules found in living organisms. It is take info account the biomass over the whole year but only represent an
Implications for agriculture
recycled through photosynthesis - producers are able to fix inorganic CO2 and instantaneous value. In early spring the biomass of zooplankton
incorporate it into organic products - and respiration - organic products eg. (protoctistans and small animals that feed on phytoplankton) may
Food chains/webs
carbohydrates, fats and occasionally proteins (containing Carbon) are broken
Carbon cycle
Ecological Energetics and exceed that of the phytoplankton. The food web is only sustainable
down to produce ATP with CO2 as a waste product. because the phytoplankton reproduce at such a rapid rate that their
Consumers gain carbon through feeding. Plant + animal tissue are rich in Carbon The finite nutrients are recycled Nutrient Cycling numbers are quickly replenished. They're more representative than
and complex organic compounds are broken down and built up in the ongoing through ecosystems. The nutrient pyramids of number but the disadvantage include problems with
- Energy flow
cycle of feeding, digestion and the assimilation of food products in animals. enters the producer within the obtaining fresh/dry mass.
Saprobiotic microorganisms (decomposers) break down organic molecules ecosystem (which is the difference Pyramids of energy (productivity), how much new material is produced
'trapped' in dead organisms during decay and decomposition, and release the bet ween that and energy flow). over a period of time. Most accurate representation but values are move
carbon as CO2 in respiration. Recycling of nutrients can be Nitrogen cycle difficult to obtain as values need to be obtained over a period of time to
Dead organisms have been preserved in environments hostile to decay - considered in terms of the elements Transfer of energy compare the before + after. Data may use kJm-2yr-1 and pyramids of
fossilisation - fossil fuels (coal/peat) contain 'locked in' carbon that hasn't been they contain, for example, carbon and bet ween living things energy are useful in comparing ecosystems which will always be a
released as the process of decay and decomposition could not take place. The nitrogen cycles. pyramid shape when stable.
carbon is released by combustion. Nitrogen is necessary to make nitrogen-containing
It was the evolution of plants in the Earth's geological history that was largely io n
) N
ae i t r ifi compounds essential for life eg. proteins, nitrogenous bases
responsible for producing the oxygen, through photosynthesis, that provided ific
at Ammonium ions (NH4+) ro
n bic c at (dna + rna) and ATP. Nitrogen enter plants as nitrate ions Decomposers/detritivores > organisms involved in decay and
mo Ammonia (NH3) b a io n
the levels of atmospheric oxygen needed to sustain complex animal life. The ( am (NO3-) absorbed from soil by AT. it is used to build the
De c
ay c t by
er
ia
decomposition. Decomposers - bacteria and fungi
balance bet ween photosynthesis and respiration has remained fairly stable nitrogen-containing organic compounds eg amino acids + Detritivores - small animals eg. earthworms, millipedes and woodice.
n)
Animal protein
t io
over the last few centuries there's been an increase in atmospheric CO2 levels nucleotides. The nitrogen-containing compounds in plants
ific a
due to an increase in the combustion of fossil fuels + deforestation. (N containing Nitrite (NO2-)
enter the consumer pathway when eaten by animals which
mo n
compounds) Consumers > obtain their energy by feeding on other organisms, animals
are then excreted (in urea), egested (in faeces), or end up in
(am
CO2 in Ph o
Nitrification by
aerobic bacteria non-living organic matter following death. are consumers. Primary consumers - feed on producers (plants).
tosy
y
atmosphere and Secondary consumers - next in the link feed on primary consumers.
De c a
nth Decay and decomposition > necessary by saprobiotic
Ea
Re s p ir e s is
dissolved in Tertiary consumers - feed on secondary consumers.
te
at io n Nitrate (NO3-) microorganisms to recycle the nitrogen contained in dead
n
oceans. in p la Plant protein Primary= herbivores. Secondary + tertiary= carnivores.
n ts organisms, excreta and faeces to its usable inorganic
(containing N
Carbon in organic form (nitrate), mineralisation.
Re compounds)
spi molecules in plants Producers > organisms that manufacture organic substances from
Re
ra
t io (producers) inorganic substances using energy. Almost all producers (plants) use
spi
Combustion ni Ammonification > decay stage ends with the production of ammonium ions (NH4+).
na
rat
nim Decomposing microorganisms (fungi + bacteria) use the nitrogen-rich compounds as light energy to produce organic compounds by photosynthesis.
Chemoautotrophs use chemical energy to produce organic
io n
als food and eventually break into ammonium ions. It is aided by detritivores like
Feeding Denitrification > Denitrification is the process
earthworms - who feed on dead organisms, breaking them into small pieces (larger compounds from inorganic materials species of prokaryotes make
in d
whereby denitrifying bacteria convert nitrates into
Carbon in SA) and help distribute the dead material through soil. organic substances using minerals in the rock as chemical energy
e co
Carbon in organic atmospheric nitrogen. This process can significantly
fossil fuels Nitritification > the conversion of ammonium ions to nitrate. The process is carried
mp
molecules in animals reduce soil fertility. Unlike nitrifying and some
out in t wo stages by t wo stages of nitrifying bacteria:
ose
n
Decay prevented
it o (consumers) nitrogen-fixing bacteria, denitrifying bacteria, for
es
Nitrifying bacteria of the genus Nitrosomonas oxidise ammonium ions to
rs
(fossilisation) eg h
n, a t example Pseudomonas, are anaerobic. Anaerobic •
io de
et d
cr an conditions are particularly likely to occur if the soil is nitrite ions (NO2-).
Ex
Carbon in organic Death compacted or waterlogged. Consequently, • Nitrifying bacteria of the genus Nitrobacter oxidise nitrite ions to nitrate
molecules in dead denitrifying bacteria are more numerous and more ions (NO3-)
organic matter active in waterlogged or very compacted soils that
are deficient in oxygen. Oxidation reactions are involved nitrifying bacteria need oxygen (the process is aerobic) to carry out nitrification. The nitrates produced by nitritification
are available in the soil to be absorbed by plants and the cycle continues. Superimposed on the process, t wo other processes; nitrogen fixation and
Nitrogen fixation
io n
)
Ammonium ions (NH4+)
N
ae i t r ifi
denitrification, which are important in the recycling of nitrogen.
c at ro
mm
o n ifi
Ammonia (NH3) bic c at
b a io n Atmospheric
De c
a y (a c t by
er
ia nitrogen Nitrogen fixation > nitrogen-fixing bacteria convert nitrogen gas in to nitrogen-containing compounds. Bacteria are mainly of the genus rhizobium and they
)
contain the enzyme nitrogenase responsible for fixing the nitrogen. Some species of nitrogen-fixing bacteria are aerobic and some are anaerobic. The
t io n
Animal protein
ific a
(N containing Nitrite (NO2-)
compounds) Denitrification nitrogen-fixing bacteria can be free living in the soil or may form mutualistic relationships with a number of plant species. Legumes may contain nitrogen-
mo n
fixing bacteria in root nodules. The legumes gain by obtaining nitrogen-containing compounds from the bacteria and the bacteria have a stable environment
(am
Nitrification by
aerobic bacteria
and a ready supply of carbohydrate. Nitrogen fixation is a very beneficial process as it enriches the soil, farmers grow legumes and allow them to decay in
y
De c a
Ea
te
Nitrate (NO3-) the soil as part of a crop rotation cycle. It can also happen because of lightning, the lightning breaks the bonds holding together the bonds in N2, and combine
n
Plant protein
(containing N with oxygen in the air forming nitrogen oxides.They dissolve in the rain, forming nitrates that are carried to the Earth. It is insignificant compared to that
compounds)
fixed by microorganisms.
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