energy and ecosystems

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  • Created by: Massu786
  • Created on: 30-11-17 17:53
Why is dry mass used when measuring biomass and why is it used to measure growth
because water content of living tissue varies, and its used to measure growth because dry mass measures increase in biological/organic material
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How do we measure dry mass?
weigh samples at intervals during drying until the weighings become constant
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How do u measure energy stored in the biomass?
using a bomb calorimeter, weigh the sample of dry material, burn in oxygen in the bomb calorimeter and the energy released is used to heat a known volume of water then record the change in temperature and calculate energy using E=mcdeltat
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What are the reasons for low efficiency of energy transfer through ecosystems?
some light is reflected/ not of appropriate wavelength, some light misses the chlorophyll, heat loss, energy loss via respiration, loss via faeces/unidigested parts, excretion
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Why do herbivores have a lower efficiency ?
they eat plants which contain a lot of cellulose which is undigestible so they use less of their food than carnivores
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What is an agriculutral ecosystem compared to a natural ecosystem?
natural ecosystem develops into a climax community, agricultural ecosystem includes domesticated animals and plants used to produce for humans
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What is the difference in energy input and productivity between agricultural and natural ecosystems?
with agricultural ecosystems you have to put in more energy to prevent the climax community forming, this energy comes from fossil fuels to plough harvest and transport crops . this increases productivity and reduces effect of limiting factors
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What are the farming practices that conserve energy ?
fertilisers provide nitrates/phosphates, pesticides to prevent crop consumption,herbicides remove competition, selective breeding, greenhouse controls living conditions, ploughing aerates soil/prevent denitrification, insecticides - simplify food web
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How does intensive rearing of livestock increase net productivity?
fed a controlled diet so high proportion of food is used for biomass, movement restricted so less energy lost in respiration, heating used so less energy used to maintain body temp, selective breeding to produce ideal livestock, predators excluded
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explain what an insecticide is and the advantages and disadvantages
chemicals that kill insects/used to simplify food web, ADV- you can control usage, fast,kills all pests, DISADV- reduces biodiversity, toxic chemicals causes bioaccumulation, can kill wrong organisms, insects can build resistance to insecticides
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explain what is meant by biological control and the advantages and disadvantages
using the natural predator,advantages- no bioaccumulation, much cheaper, one off application, no resistance forms so works over a long time, maintains low population of pests. disadvantages - doesnt kill all the pests and much slower process
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what is the equation for net production ?
N=I-(F+R) , net production=chemical energy ingested in food -(energy lost in faeces and respiration)
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what is the equation for percentage efficiency ?
energy available after the transfer/ energy available before the transfer X 100
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describe the process of nitrogen fixation
nitrogen fixing bacteria in the soil or root nodues of legumes convert N2 gas into ammonium. Theres a mutualistic relationship between plant + bacteria in root nodules, plant provides bacteria with glucose, bacteria converts N2 to ammonium for plant
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What do plants use this ammonium for and what happens after?
They convert it into amino acids and proteins used for growth and to make nucleic acids. Animals will ingest the plant and digest the proteins into amino acids and other nitrogen containing compounds when they excrete
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describe the process of ammonification
these nitrogen containing compounds (proteins, urea, nucleic acids) are broken down into ammonia which go on to form ammonium ions by saprobiontic bacteria and fungi which secrete extracellular digestive enzymes
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describe the process of nitrification
aerobic nitrifying bacteria convert ammonium ions to nitrite ions (NO2-)then to nitrate ions (NO3-)through oxidation. The nitrates produced can enter the roots of plants by active transport. Oxygen needed for this farmers plough to keep soil aerated
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describe the process of denitrification
denitrifying bacteria thrive in anaerobic conditions in water logged soils. They convert the nitrates into nitrogen gas again using respiration.
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What is phosphorus needed for and where is it found?
it is needed to make phopholipids, ATP and nucleic acids. Phosphorus is found in sedimentary rocks and dissolved in oceans in the form of phosphate ions .
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describe the phosphorus cycle
phosphate ions released into soil/lakes by weathering,taken in by plants + aquatic producers,transferred through food chain, saprobionts break down faeces to release phosphate ions, guano-waste of sea birds returns phosphate ions to soil
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what is the role of mycorrhizae
associations between fungi and roots of plants, fungi act as extensions of plant root, increase SA, mycorrhiza holds water and minerals close to roots so it can absorb it easily, helps uptake of scarce ions e.g phosphate ions,mutualistic relationship
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Why do we need fertilisers?
crops take in minerals and then are harvested from the original field they were grown in so they are not returned to the soil by decomposers so we need to use fertilisers to replenish these mineral ions
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How do fertilisers increase productivity?
nitrogen is used in amino acids, ATP and DNA, ATP is needed for photosynthesis to make organic matter, nitrates needed to grow larger SA of leaf more photosynthesis more organic matter produced, phosphates used to make ATP from ADP and Pi,
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What are the advantages of natural fertilisers?
less leaching, increases organic content of soil, improves drainage, contains other elements, less expensive than artificial fertilisers
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describe the process of leaching
when nutrients dissolve into rainwater and deep into the soil and go to lakes and rivers. This can cause eutrophication
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describe the process of eutrophication
leaching/fertilisers cause algal bloom, blocks light/more competition for light /less photosynthesis/plants die, increase in saprobionts-use up o2 when they decompose plants, oxygen limited, so aerobic organisms die
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How does the low oxygen concentration lead to increase in nitrate production and what else does it lead to?
aerobic organisms dying leads to more anaerobic organisms because theres less competition. anaerobic organisms decompose dead material and releases a lot of nitrates. it changes biodiversity usually lowers species diversity
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What are the effects of fertilisers?
nitrogen fertilisers reduce species diversity because nitrogen rich soil favour certain species, leaching which leads to eutrophication, pollution of watercourses, changes natural balance of nutrients in soil which can cause plants to die
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what is the role of bacteria in making nitrogen in dead matter available for growing plants
saprobionts break down nitrogen containing compounds using extracellular digestion , ammonia produced converted to ammonium ions then nitrite then nitrate by nitrifying bacteria using oxidation
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Other cards in this set

Card 2

Front

How do we measure dry mass?

Back

weigh samples at intervals during drying until the weighings become constant

Card 3

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How do u measure energy stored in the biomass?

Back

Preview of the front of card 3

Card 4

Front

What are the reasons for low efficiency of energy transfer through ecosystems?

Back

Preview of the front of card 4

Card 5

Front

Why do herbivores have a lower efficiency ?

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