Topic 5B: Energy Transfer and Nutrient Cycles Flashcards

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1
Q

What are biotic factors?
Give an example

A
  • Living
    e.g. predators, food availability, pathogens
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2
Q

What are abiotic factors?
Give an example

A
  • Non-living
    e.g. temperature, light availability, water availability, pH, salinity
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3
Q

Define ecosystem

A
  • All organisms and the biotic & abiotic factors in an area
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4
Q

Define population

A
  • All organisms of one species in a habitat
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5
Q

Define community

A
  • All organisms of all species in a habitat
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6
Q

Define habitat

A
  • The place an organism lives
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7
Q

Define niche

A
  • The role of a species in an ecosystem
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8
Q

Define trophic level

A
  • Each stage of a food chain
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9
Q

What productivity values do plants have?

A
  • GPP -> total amount of energy made by a producer (units = given area per unit time - kJ/m^2/yr)
  • NPP -> biomass accumulated
  • R -> respiratory losses
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10
Q

How is NPP calculated?

A

NPP = GPP - R

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11
Q

What productivity values to animals have?

A
  • I -> total energy ingested
  • R -> respiratory losses
  • F -> faeces and urine
  • N -> net productivity
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12
Q

How is net productivity (N) calculated?

A

N = I - (R + F)

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13
Q

How do you calculate energy transfer efficiency?

A
  • N/I x100
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14
Q

How is energy lost from the sun to a producer?

A
  • Light reflected
  • Not all light shines on photosynthetic areas
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15
Q

How is energy lost between producers and primary consumers?

A
  • Respiration
  • Heat
  • Not all of the producer eaten - e.g. deep roots
  • Some not digested - e.g. cellulose
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16
Q

How is energy lost between consumers?

A
  • Respiration, heat
  • Not all eaten - e.g. bones
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17
Q

How do you make dry biomass?

A
  • Put in an oven on a low temperature - prevent combustion
  • Regularly measure the mass
  • When the mass remains constant - all the water has been removed - now dry
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18
Q

What unit do you measure dry biomass in?

A

kg/m^2

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19
Q

Describe calorimetry

A
  • Estimates the amount of energy stored in dry biomass
  • Burn a sample of dry biomass completely to heat a known volume of water
  • Change in temperature is used to calculate the chemical energy of the dry biomass
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20
Q

What is mass of carbon?

A
  • Organisms are made of organic compounds that contain carbon
  • Mass of carbon is a good biomass indicator
  • Very difficult to measure
  • Mass of carbon is around 50% of dry biomass
  • Measured in kg/m^2/yr - accounts for seasonal changes
21
Q

What are the two types of decomposers?

A
  • Saprobiotic microorganisms -> extracellular digestion - secrete enzymes to hydrolyse molecules - then absorb the smaller molecules produced (fungi, bacteria etc)
  • Detritivores -> feed on dead / decaying matter, digest in the body (earthworms, maggots etc)
22
Q

In farming what are 2 methods of reducing lost energy?

A
  • reducing energy lost to other organisms
  • reducing energy lost through respiration
23
Q

What are ways of simplifying food webs?

A

Chemical pesticides
- Insecticides -> kill pests, less biomass lost, grow more, inc NPP
- Herbicides -> kill weeds, removes direct competition, removes pest food sources
Biological agents
- Parasites -> Kill insect / reduces its function, live or lay eggs on pest, viruses / bacteria - kill pests

24
Q

How are these methods of simplifying food webs best used?

A
  • As integrated systems
  • Use both chemical and biological
  • Reduces pest numbers further than one method alone
  • Even more inc in NPP
25
Q

What are ways of reducing respiratory losses?

A

Controlling conditions
- Restrict movement -> Small pens, indoors, warm
- Less energy wasted on maintaining body temperature
- More biomass produced, inc NP and energy transfer efficiency

26
Q

What are the benefits of reducing respiratory losses?

A
  • More food produced in less time
  • Lower cost
27
Q

What are issues with methods of reducing respiratory losses?

A
  • Ethics
  • Pain, distress caused
  • Restricts the natural behaviour of animals
28
Q

Why are fertilisers needed?

A
  • Crops take in minerals from soil as they grow
  • When they are harvested these are taken with them
  • They do not die and decompose there - nutrients not recycled back in by decomposers
  • Nutrients also lost as animals eat plants and are then moved away
29
Q

What do fertilisers do?

A
  • Replace lost minerals and increase energy efficiency
30
Q

What are artificial fertilisers?

A
  • Inorganic
  • Pure chemicals
  • Powders / pellets
31
Q

What are natural fertilisers?

A
  • Organic matter
  • Manure, composted vegetables, crop residue, sewage sludge
32
Q

What are issues with fertilisers?

A
  • Too much applied - overflow leaches into waterways
  • Happens when fertiliser applied before heavy rainfall
  • Change the nutrient balance of the soil - can cause crop death
33
Q

How do natural fertilisers have less issues?

A
  • Minerals are contained in organic molecules
  • They need to be decomposed first
  • Cause a more controlled release - less likely to leach away
34
Q

What nutrients are less likely to leach?

A
  • Phosphates
  • Less soluble
35
Q

What causes eutrophication?

A
  • Excess nutrients
36
Q

Describe the process of eutrophication

A
  1. Mineral ions from fields cause rapid algal growth
  2. Algae blocks sunlight from reaching plants below
  3. Plants die as they cannot photosynthesise
  4. Bacteria feed on dead plants - aerobically respire reducing O2 concentration
  5. Fish & aquatic organisms die - not enough dissolved O2
37
Q

How do fungi help plants?

A
  • Form symbiotic relationships with plant roots - mycorrhizae
  • Long, thin strands (hyphae) - inc SA to absorb ions and water
  • Fungi gain compounds such as glucose from the plant
38
Q

Describe the nitrogen cycle

A

nitrification nitrification denitrification
[Ammonium ions] —-» [nitrites] —-» nitrate —-» N2 in air
^ feeding l absorption l
l (animals)«—– (plants)«———-
l death & excretion l l death nitrogen
——————————–(decomposers) fixation
ammonification

39
Q

What things contain nitrogen compounds?

A
  • Proteins
  • DNA
40
Q

What is nitrification?

A
  • Ammonium ions to nitrogen compounds for plants - oxygen added
  • Done by nitrifying bacteria
41
Q

What is denitrification?

A
  • Nitrates in the soil are converted to nitrogen gas
  • Done by bacteria
  • In anaerobic conditions only –> aerate soil, not waterlogged
42
Q

What is nitrogen fixation?

A
  • Nitrogen from the atmosphere turned to nitrogen containing compounds
  • Done by bacteria in the root nodules of leguminous plants
  • N2 -> ammonia -> ammonium ions
  • Form a mutualistic relationship
43
Q

What is ammonification?

A
  • Saprobionts turn nitrogen compounds from dead organisms into ammonia
  • Also done to animal waste
44
Q

Describe the phosphorus cycle

A

(fish)—-»(birds) (plants)———–»(animals)
l l / \ / \
(algae) [guano]—-»[soil]«–(decomposers)«–[urine&]
l ^ [faeces]
[seas&] l
[lakes] «——————- [rock]

45
Q

What things contain phosphates?

A
  • DNA
  • ATP
  • Phospholipids
46
Q

How are phosphates released from rocks?

A
  • Weathering releases phosphates from rock to soil and bodies of water
47
Q

How do plants obtain phosphates?

A
  • Absorb them through the roots from the soil
48
Q

How do phosphates travel from the sea to the soil again?

A
  • Phosphates taken in by aquatic producers
  • Passed along the food chain to fish and then sea birds
  • Waste from sea birds - guano - high proportion of phosphates which are returned to the soil
  • Often used as a natural fertiliser