lecture 22: ecosystem processes Flashcards

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1
Q

What are ecosystems?

A

Multiple populations of organisms that live in an area + Abiotic components (soil, water, atmosphere)

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2
Q

What arethe ecosystem processes?

A

Biotic + abiotic components of ecosystem are linked by:
1. FLOW of energy: energy dissipates as it flows through ecosystems
2. CYCLING of nutrients: nutrients cycle within ecosystems
—> Food webs: primary producers, decomposers, consumers (primary, secondary…)

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3
Q

Gross (GPP) vs Net primary production (NPP)

A

Total incoming solar energy —> Gross primary production (GPP) 0.8% of total solar energy
- Small percentage because:
1. Not all light hist photosynthetic tissue & pigments in photosynthetic tissue cannot capture all wavelengths
2. Rate of photosynthesis can decrease du to environmental conditions
—> Net primary production (NPP) 45% of GPP
- NPP = GPP - R (energy used for maintenance of primary producers; cellular respiration, released as heat)

GPP = Total primary production in an ecosystem
NPP: energy invested in production of biomass; converted into organic materials

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4
Q

Why si NPP so important?

A

Sets ecosystem’s energy budget

Represents amount of energy AVAILABLE to consumers and decomposers as BIOMASS

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5
Q

What limits primary production in terrestrial ecosystems?

A
  1. Temperature: high T = better, more active
  2. Moisture: more water = better, more active

High quantity of primary production: tropical rainforests
Low: deserts, arctic regions

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6
Q

What limits primary production in aquatic ecosystems?

A
  1. Inorganic nutrients: limited nutrients
  2. Sunlight: filtered, only certain wavelengths of light are available underwater

High quantity of primary production: coral reefs, algal beds, coast lines
Low: open ocean

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7
Q

What is eutrophication?

A

Large increase in populations within a trophic level —> bloom in growth of primary producers (algae or cyanobacteria)

  • Excess nitrogen or phosphorus nutrients
  • Natural cause or human induced
  • Change in color
  • Red Tides —> oxygen dead zones/accumulation of toxins —> too much biomass, all O2 used by decomposers, not enough O2 for fish —> eutrophication in lakes —> lead to loss of many fish species
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8
Q

What is secondary production?

A

Amount of chemical energy in consumers’ food that is converted to new biomass

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9
Q

What is an organism’s production efficiency?

A

Percentage of energy assimilated by an organism that becomes incorporated into new biomass

  • Need to remove energy used for cellular respiration, maintenance of organism
  • Vertebrates have LOWER PRODUCTION EFFICIENCIES than invertebrates —> because need MORE energy for cellular respiration and to maintain body
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10
Q

Describe an ecosystem’s pyramid of production

A
  • Energy transfer between trophic levels
  • Total biomass = greatest at the lowest trophic level (primary producers) and declines at higher levels
  • Trophic-level transfer efficiency = only 5-20%
  • Pyramid: less and less biomass/energy, but organisms get larger and larger —> Stop at tertiary/quaternary consumers bc cannot support another trophic level
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11
Q

Why doesn’t all the energy get transferred between trophic levels? (2)

A
  1. Energy in food consuemed = used/lost and not transferred for secondary production —> lost as heat
    - Used for maintaining life activities via cellular respiration
    - Lost in undigested material (feces)
  2. Not all of the biomass in lower trophic level is consumed by next trophic level
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12
Q

Consequence of low efficiency transfer? (2)

A
  1. Production can only support 3-4 upper trophic levels

2. Major limitation of food chain length

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13
Q

What is biomagnification?

A
  • Chemical pollutants (persistent organic pollutants; POPs) produced by humans = NOT broken down & accumulate in fatty (lipid) tissues of animals
  • POPs increase in concentration (bc less biomass) as they are transferred between trophic levels —> BIOMAGNIFICATION
  • High concentrations of POPs can poison upper level consumers + humans that eat them
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14
Q

What is nutrient cycling?

A

Biogeochemical cycle (phosphorus, sulfur, water, carbon, nitrogen cycles) = moving of elements from abiotic environment through organisms and back again

  • Nutrients can be;
    1. Inorganic or organic
    2. Available or unavailable
  • Compounds can be transformed and moved from one reservoir to another
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15
Q

What is global cycling?

A
  1. Cycle with elements with gaseous phases, globally: carbon, oxygen, nitrogen, sulfur cycle
  2. Cycle with elements with no gaseous phase: phosphorus, potassium, calcium (less mobi;le, cycle locally in terrestrial systems but more broadly when dissolved in aquatic systems)
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16
Q

What is the carbon cycle?

A
  • Biological importance: carbon-based organic molecules are essential to all organisms
  • Forms available to life: photoautotrophs (photosynthesis) convert CO2 to organic molecules that are used by heterotrophs
  • Reservoirs: biomass, fossil fuels, soils, sediments, solutes in oceans, atmosphere, rocks
  • Processes: carbon compounds are transformed in photosynthesis, cellular respiration and decomposition, volcanic activity and burning of fossil fuels contribute to CO2 to the atmosphere, deforestation (burn wood = more CO2)
  • COS is transported as a gas in atmosphere and dissolved in water
17
Q

What is the nitrogen cycle?

A
  • Biological importance: amino acids and nucleotides contain nitrogen, nitrogen mineral nutrients are often limiting in primary production
  • Forms available to life: primary producers assimilate inorganic forms (ammonium NH4+ and nitrate NO3-) and some organic forms (amino acids), various bacteria can uses all these + nitrite (NO2-) —> IN NITROGEN FIXATION, animals can only use organic forms
  • Reservoirs: main = atmosphere 80% or N2, need NITROGEN FIXATION (N2 —> NH3) to be used in ecosystem, other reservoirs of inorganic and organic compounds = soils, sediments of lakes, rivers, oceans, biomass of living organisms
  • Processes: assimilation, consumption, decomposition, nitrogen fixation, ammonification (organic nitrogen —> NH4+), nitrification (NH4+ —> NO3-), denitrification (NO3- —> N2)
    —> Most conversions carried out by BACTERIA (part of their metabolisms)
18
Q

Human impacts in carbon cycle?

A

“Locked away” carbon —> mine them and use them

- Gas for cars so more CO2

19
Q

Human impacts in nitrogen cycle?

A

Agriculture: fertilizers —> create N gases —> then end up in water —> algal and cyanobacteria blooms

20
Q

Why conserve biodiversity? (4)

A
  1. Prevent extinction: humans depend organisms for food, medicine, industrial products, tools in research
  2. Maintain healthy (stable and productive, can withstand changes) and diverse ecosystems: humans depend on essential ecosystem services clean air, water)
  3. Culture (parks), leisure
  4. Ethical responsibility to protect other life forms
21
Q

What is extinction? 2 types?

A
  • Natural process that has been documented throughout history of life
    1. Background extinction: ≈ 1-2 species extinct every 100 years
    2. Mass extinctions: 5 documented from fossil record
22
Q

Why are we in a biodiversity crisis right now?

A
  • Past 100 years: several species have gone extinct
  • Today: >20 000 species are threatened with extinction
  • We are experiencing a 6th mass extinction that is human-induced
23
Q

How are we causing extinction?

A
  1. Climate change
  2. Pollution
  3. Exploitation: largely reducing populations
  4. Habitat degradation
  5. Invasive species and disease: introduced to new habitat, but environment is not made for it (human-induced)
24
Q

How is genetic drift a concern for conservation biology?

A
  • Many pop. = getting reduced in size by habitat destruction/fragmentation
  • Small pop. = Subject to MORE genetic drift
  • Pop. become LESS FIT as “low fitness” alleles become fixed by chance (random)
  • Pop. with lower fitness = MORE subject to EXTINCTION