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General Ecology > Lecture 17: Ecosystems: Energy transfer and Net Primary Production (NPP) > Flashcards

Lecture 17: Ecosystems: Energy transfer and Net Primary Production (NPP) Flashcards

1
Q

define ecosystem

A

Ecological scale at which we see the exchange of common elements among organisms and the environment.

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2
Q

what is the unique process seen at the ecosystem level

A

energy flux and nutrient cycling

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3
Q

what is the primary energy transformation in ecosystems

A

the conversion of light into energy via photosynthesis

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4
Q

Ecosystem _____ and _________________ both increase the amount of energy an ecosystem needs to be sustained

A
  • size
  • speed of energy flow
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5
Q

what is lost with each transfer to a higher trophic level and why

A
  • energy is lost with each transfer to a higher trophic level
  • bc of the work organisms have to do to acquire and use energy
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6
Q

define trophic pyramid

A
  • Graphical representation of the relative energy or biomass at each trophic level
  • visualizes loss of energy between trophic level
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7
Q

Pyramids of energy and biomass in terrestrial systems

A

Energy and biomass pyramids are the same shape (pyramid shape) because of large, relatively long lived primary producers.

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8
Q

Pyramids of energy and biomass in aquatic systems

A
  • energy pyramid is a regular pyramid
  • Biomass pyramid is inverted because of tiny, short-lived primary producers compared to large, long lived consumers.
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9
Q

Tracing energy to reveal real trophic levels

A
  • Ratio of different Nitrogen isotopes (15N/14N) changes with trophic level
  • more of the heavier isotope means nitrogen was acquired from a higher trophic level
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10
Q

what does analyzing the isotope ratio reveal

A

reveals trophic level without the need for direct observations

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11
Q

nitrogen isotope ratio ant discovery

A

most canopy ants are herbivores bc they had more 14N (lighter than 15N)

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12
Q

Three main reduction steps

A
  1. Consumption Efficiency
  2. Assimilation Efficiency
  3. Net Production Efficiency
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13
Q

define consumption efficiency

A
  • percentage of energy in a trophic level that is consumed by the next higher trophic level
  • not everything is eaten.
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14
Q

define assimilation efficiency

A
  • percentage of consumed energy that is assimilated into the organisms in the consumer trophic level
  • not everything that is eaten is used by the organism.
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15
Q

define net production efficiency

A
  • percentage of assimilated energy directed to growth and reproduction of the consumer trophic level
  • not everything used by the organism contributes to growth and reproduction
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16
Q

define egested energy

A

indigestible foods that are defecated or regurgitated

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17
Q

define assimilated energy

A
  • What is actually assimilated
  • used to calculate assimilation efficiency
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18
Q

respired energy

A

the component of assimilated energy that is used in respiration

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19
Q

excreted energy

A

the organic waste due to the proportion of assimilated energy that cannot be used bc it is in excess

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20
Q

net production efficiency “equation”

A

Assimilation Efficiency = respiration - excretion

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21
Q

Which plant parts allow for the highest assimilation efficiency?

A

Seeds > Young leaves > Grazing and browsing > Decaying plant material (detritivores)

22
Q

The ________ in food also influences assimilation efficiency and especially the amount of energy lost in excreted energy.

A

balance of nutrients

23
Q

stoichiometry

A

The study of the balance of nutrients in organisms, and ecological systems as a whole

24
Q

Nutrient imbalances in an organism’s diet, and the resulting excess excretion, can greatly reduce assimilation efficiency — but can have ____________________________

A

other (positive) consequences

25
Detritivores form the primary consumers of an additional ________, parallel to the __________ involving herbivores feeding on living plants
- “brown food web” - “green food web”
26
Nutrient cycling through the detritivore food web tends to be ______, but _________ for ecosystem stability.
- slower - very important
27
since measuring all the energy in an ecosystem is not possible, what do we do instead
need to use “proxies” of various kinds that inform us about the properties of the whole ecosystem
28
One good proxy approach for all the energy in an ecosystem is to look at the ____________ through _____________________.
- energy-flow rate - part of the ecosystem
29
what do energy flow rates tell us
how long energy stays in one trophic level, and therefore how much energy and biomass can accumulate within an ecosystem
30
define energy residence time
The length of time energy stays in a given trophic level
31
what can tell us critical things about the functioning of an ecosystem
Residence time of energy, biomass, or any key nutrient
32
define primary production
the accumulation of energy by plants and other autotrophs
33
define gross primary production
- The measure of all the energy assimilated by the plant - much is used in respiration
34
define net primary production
- the energy accumulated as plant biomass - the part of primary production available to the next trophic level.
35
3 approaches for practical measures of net primary production to assess energy flow
1. measured by harvesting 2. measured by recording carbon dioxide uptake rates 3. measured at large spatial scales using remote sensing
36
practical measures of net primary production - harvesting
- can be measured by harvesting, drying, and weighed biomass produced in particular areas - can measure aboveground or below ground biomass.
37
practical measures of net primary production - recording carbon dioxide uptake rates
- can be measured by recording carbon dioxide uptake rates under small-scale, controlled conditions — a direct measure of photosynthesis and ultimate biomass accumulation - oxygen uptake and release rates are used in aquatic systems
38
practical measures of net primary production - at large spatial scales using remote sensing
- can be measured at large spatial scales using remote sensing of vegetation cover - rapidly advancing method driven by technological development.
39
Global patterns of NPP in terrestrial and aquatic systems using remote sensing data
- terrestrial systems, highest NPP occurs in the tropics - Highest NPP in aquatic systems occurs in shallow waters around land
40
what is Net Primary Production influenced by
- the availability of all key inputs to photosynthesis and plant growth: - light - nutrients - water availability and temperature
41
Influences and limits on Net Primary Production - light
- light availability will limit NPP up to the “saturation point” - point at which no more light can be used by photosynthetic pigment
42
Influences and limits on Net Primary Production - nutrients
Plants are adapted to typically available nutrients, but seasonal or human-driven pulses in nutrients will increase NPP
43
what does low moisture in plants result in
- wilting (water uptake less than loss via transpiration) - plants close their stomata to reduce water loss.
44
what does a closed stomata do
limits carbon dioxide uptake, severely limiting photosynthesis
45
how is production a reflection of water availability
Many wild plant species vary little in water use efficiency (~2g used per kg of rainfall)
46
what does water-use efficiency interact with
annual rainfall patterns and temperature/annual growing period to determine NPP
47
ideal conditions for high NPP
warm temperatures and moderate, consistent rainfall
48
Hotter places have higher NPP, but ______ water reduces nutrient availability (erosion and runoff) and lowers NPP.
too much
49
Net secondary productivity
the rate of biomass accumulation in consumers
50
what does NPP dictate
the net secondary productivity of ecosystems

General Ecology (23 decks)

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