3-Ecosystem Flashcards

1
Q

ECOSYSTEM

A

a biotic community and its abiotic environment

  • can be small or large
  • ecosystem ecologists ask:
    • how does energy flow through a system
    • how do nutrients cycle between the abiotic and biotic components of a system?
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2
Q

PRODUCERS

A
  • aka autotrophs
  • obtain their energy by using photosynthesis to convert solar energy to chemical energy
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3
Q

CONSUMERS

A
  • aka heterotrophs
  • obtain energy by eating other organisms
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4
Q

what are the two types of consumers that eat dead organic material

A
  • detritvores—ingest dead organic material, break down material internally
    • earthworms, slugs
  • decomposers—break down dead organic material, then absorb nutrients
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5
Q

FOOD CHAIN

A

the linear transfer of food energy from one trophic level to the next trophic level

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6
Q

food web

A

food web—series of interlocked food chains that allow for the possibility of omnivores (consumers of multiple trophic levels)

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7
Q

primary productivity

A
  • rate of conversation from solar energy to chemical energy by producers
    • biomass/area/time
    • energy/area/time
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8
Q

gross primary productivity (GPP)

A

absolute rate of primary productivity

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9
Q

net primary productivity (NPP)

A

rate of primary productivity after accounting for cellular respiration

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10
Q

ten percent rule

A

approximately 10% of the chemical energy at one trophic level is transferred to the next trophic level

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11
Q

why is energy lost between trophic levels?

A
  • not all of the organisms at one trophic level are consumed by organisms at the next trophic level
    • ~90% of producer biomass is consumed by detritivores and decomposers
  • not all food eaten is completely digested
  • energy is lost as heat (by-product of metabolism)
  • energy used for hunting
  • this creates a biomass pyramid
    • it takes MAAANY primary producers to support only a few teritary consumers
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12
Q

what are the nutrients that are chemicals needed for growth and maintenance for life

A
  • N (nitrogen)
  • P (Phosphorus)
  • C (Carbon)
  • O (Oxygen)
  • Fe (iron)

nutrients do not come from outside the earth and instead have to be recycled

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13
Q

pools

A

where nutrients are stored

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14
Q

fluxes

A

movement in and out of pools

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15
Q

Carbon

A
  • essential nutrient that is required for growth and reproduction
  • basic building block of organic molecules
  • mainly stored in oceans and atmostphere
    • soils, living organisms, and fossil fuels are also important pools of C
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16
Q

how does
Carbon enter and exit the food web?

A
  • enters plant—C(CO2) captured by plants during photosynthesis, incorporated into organic molecules
  • enter animals—Carbon is passed along the food chain/food web by consumers
  • reenters the atmosphere
    • cellular respiration—occurs in the cells of all living things: producers (autotrophs) and consumers (heterotrophs)
    • humans are also emmiting carbon-based greenhouse gases to the atmosphere through deforestation and fossil fuel use
17
Q

Nitrogen

A
  • essential nutrient that is required for survival and growth of all living organisms
  • vast majority is stored in atmosphere as N2
    • 80% of the atmosphere!!
  • soils, oceans, and living organisms are also important pools of N
18
Q

why is nitrogen a limiting factor?

A
  • atmospheric nitrogen is largely inaccessible by most organisms
    • triple bond takes a lot of energy to break!
    • plants and animals cannot break these bonds
  • sooooo N is a scarce resource
    • often limits primary productivity in many ecosystems
19
Q

limiting factor

A

a factor that limits the growth, abundance, or distribution of individuals and/or populations

20
Q

how does N become biologically available?

A

nitrogen fixation
- a process where N2 is converted into NH3
- ammonia

nitrification
process where NH3 is converted to nitrites (NO2) and then nitrates (NO3)

21
Q

how does nitrogen enter plants without symbiotic bacteria?

A
  • some nitrogen-fixing bacteria are free-living in the soil or ocean while others form a symbiotic relationship with plants
    • free-living nitrogen-fixing bacteria that convert gaseous nitrogen to ammonia
    • nitrifying bacteria that convery ammonia to nitrites and nitrates
    • decomposing bacteria that breakdown dead organic material/tissues into basic components
  • plants can uptake biologically available nitrogen via their roots
22
Q

how does nitrogen enter animals?

A
  • plants eaten by primary consumers!
  • passed along food chain/web
23
Q

other components of the nitrogen cycle

A
  • when plants/animals die, tissues are decomposed by decomposing bacteria, which released nitrogen back into the ecosystem in a usable form
  • when animals pee/poop, they release nitrogen into the environment in a usable form
24
Q

how does nitrogen return to the atmosphere?

A
  • denitrification—process that converts nitrates to nitrogen gas
  • denitrifying bacteria—strip O from NO3 (nitrates) and NO2 (Nitrites) and release N2 back to atmosphere
25
Q

how are Humans disrupting the nitrogen cycle

A
  • increase the amount of biologically available nitrogen in ecosystems
  • excess nitrate is getting into water as a result of runoff from agricultural areas
    • resulting in eutrophication of water bodies
      • gradual increase in nitrogen (and other nutrients) in aquatic ecosystem
  • the addition of nitrogen due to human activities has lead to excessive plant and algae growth due to increased availability of nitrogen
    • can lead to decreased diversity
    • dead zones!