Section 5: Energy and Ecosystems + Nutrient Cycles Flashcards

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1
Q

How do different types of autotrophs (producers) to synthesise their own food

A
  • Photoautotrophs use light energy and chemoautotrophs use inorganic molecules
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2
Q

How can biomass be measured?

A
  • Mass of carbon
  • Dry mass of tissue per given area
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3
Q

How is dry mass of tissue obtained?

A
  • Sample of organism dried in an oven set to a low temperature
  • Sample reweighed at regular intervals
  • All water is removed when mass remains constant
  • Mass of carbon is 50% of dry mass
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4
Q

How is dry mass more representative

A
  • Because water content of sample varies
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5
Q

How do you measure the chemical energy stored in dry biomass using calorimetry

A
  • Sample of dry biomass is burnt
  • Energy released is used to heat a known volume of water
  • Change in temperature of water is used to calculate the chemical energy
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6
Q

What is gross primary production?

A
  • Chemical energy store in plant biomass in a given area/ volume in a given time
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7
Q

What is net primary production?

A
  • Chemical energy store in plant biomass after respiratory losses to the environment
  • NPP - GPP - R
  • NPP is available for plant growth and reproduction
  • The NPP is also available to other trophic levels in the ecosystem
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7
Q

What is net primary production?

A
  • Chemical energy store in plant biomass after respiratory losses to the environment
  • NPP - GPP - R
  • NPP is available for plant growth and reproduction
  • The NPP is also available to other trophic levels in the ecosystem
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8
Q

How do you work out the net production of consumers?

A
  • N = I - (F+R)
  • I = The chemical energy store in food
  • F = The chemical energy lost to the environment as faeces and urine
  • R = Respiratory losses
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9
Q

What are the units of rate productivity

A

KJ ha-1year-1

  • KJ = unit of energy
  • Per unit area (ha) = different environments vary in size
  • Per year = more representative as it takes into account the effect of seasonal variation on biomass so environments can be compared
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10
Q

Why is the energy transfer between the sun and producer inefficient

A
  • Wrong wavelength of light
  • Light does not hit chlorophyll
  • Light is reflected back into space
  • Lost as heat
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11
Q

Why is the energy transfer between producer - primary consumer - secondary consumer inefficient

A
  • Respiratory loss - for metabolism
  • Lost as heat
  • Not all plant/ animal eaten e.g bones
  • Some food not digested - faeces
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12
Q

What are some farming practices that increase energy efficiency in crops?

A
  • Simplifying food webs to reduce energy/ biomass losses to non-human food chains
  • Herbicides - kill weeds - less competition - more energy to create biomass
  • Fungicides
  • Pesticides
  • Fertilisers
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13
Q

What are some farming practices that increase energy efficiency in livestock?

A
  • Restrict movement
  • Keep warm
  • Slaughter when young
  • Selective breeding
  • Treated with antibiotics to prevent loss of energy due to pathogens
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14
Q

What is the role of saprobionts in recycling chemical elements?

A
  • Feed on remains of dead plants/ animals and their waste products and break down organic molecules
  • By secreting enzymes for extracellular digestion - absorb soluble nutrients
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15
Q

What is the role of mycorrhizae in recyling chemical elements

A
  • Symbiotic relationship between fungi and roots of plants = mycorrhizae
  • Fungi acts as an extension of the plant roots - increase surface area - absorption of water
  • Mutualistic relationship - plant provides fungi with carbs
16
Q

What are the main stages of the nitrogen cycle?

A
  • Nitrogen Fixation
  • Ammonification
  • Nitrification
  • Denitrification
17
Q

What is Nitrogen Fixation?

A
  • Nitrogen gas converted to nitrogen containing compounds e.g ammonia
  • By nitrogen fixing bacteria
    • Can be free living in the soil
    • Or mutualistic - nodules on roots of legumes. Plant gets amino acids and bacteria gets carbs
18
Q

What is ammonification?

A
  • Nitrogen containing compounds e.g proteins from dead organisms is broken down
  • Converted to ammonia which forms ammonium ions
  • By saprobionts
19
Q

What is Nitrification?

A
  • Ammonium ions in the soil turn into nitrites then nitrates by nitrifying bacteria
  • Bacteria need oxygen
  • Nitrates absorbed by plant root hair cells by active transport
  • Adding more O2 - nitrifying bacteria increases and denitrifying to decrease
20
Q

What is denitrification?

A
  • Nitrates in the soil - nitrogen gas by denitifying bacteria - anaerobically respire
21
Q

What is the importance of the nitrogen cycle?

A
  • Nitrogen gas is unreactive and not easily converted into other compounds
  • Nitrates can be used to make proteins and nucleic acids for growth
22
Q

What are the stages of the Phosphorous cycle?

A
  • Phosphate ions in the rocks released by erosion/weathering
  • Phosphate ions taken up by plants into their biomass
  • Phosphate ions transferred through food chain
  • Some phosphate ions lost in waste products - saprobionts decompose
  • Weathering of rocks can release phosphate into seas, lakes and rivers