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ecology and conservation > ecosystems, biogeochem & 1º production > Flashcards

ecosystems, biogeochem & 1º production Flashcards

& energy transfer

1
Q

how can all ecosystems be understood?

A
  • in terms of transfer and transformation of energy and matter
  • energy flows one way through ecosystem
  • cycling of matter within ecosystem
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2
Q

First Law of Thermodynamics

A
  • energy cannot be created or destroyed …
  • only transferred / transformed
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3
Q

Second Law of Thermodynamics

A

entropy of a closed system always ↑ (or remains constant)

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4
Q

summary of energy in an ecosystem

A
  1. energy enters most ecosystems as solar radiation…
  2. and is transformed by p/s into chemical energy…
  3. which is transferred between trophic levels and everntually lost as heat
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5
Q

entropy

A

measure of disorder in a system

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6
Q

-ves of thermodynamics

conservation of energy law

A
  • energy flows through ecosystems -> cannot be cycled / recycled
  • energy transfer is inefficient between trophic levels –> energy used and some is always lost
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7
Q

law of mass conservation

A
  • mass is neither created nor destroyed
  • elements can be combined into molecules but cannot be created or transformed
  • chemical elements (C, N, O, etc.) exist in env, can be incorporated into organisms, and can be recycled
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8
Q

how is recycling of chemicals facilitated?

A

by activity of detritivors and decomposers

  • detritivors feed on dead organic material
  • decomposers further break down organic material left behind by detritivors into simpler substances
  • closed nutrient cycle -> nutrients recycled back into soil, then used by living organisms again

^without them, organic matter would pile up until available elements are exhausted

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9
Q

ecosystem

A
  • ecological community
  • and abiotic env with which it interacts
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10
Q

conservation of energy law

in an ecosystem

A
  • refers to principle that energy is neither created nor destroyed within the system…
  • but is instead transferred / transformed from one form to another
  • this concept is derived from 1st law of thermodynamics: states that total energy in a closed system remains constant
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11
Q

weathering

A
  • caused by atm (wind and water) and wildlife
  • may be physical (heat, water, ice, pressure) or chemical (biological or atmospheric)
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12
Q

erosion

A

transportation and deposition of weathered material (e.g. by wind and water)

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13
Q

nutrient enrichment

A
  • human activities (eg. in agriculture) can lead to movement of nutrients across diff parts of biosphere
  • most biogeochemical cycles now disrupted/dominated by human activities
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14
Q

describe toxic effects of excess nutrients

A

eg. Mississippi River carries nitrogen pollution to Gulf of Mexico -> causing summer phytoplankton blooms

When phytoplankton die: their decomposition creates a “dead zone” with low oxygen levels along the coast

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15
Q

dead zone

A
  • areas of water where aquatic life cannot survive …
  • due to low oxygen levels
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16
Q

consequence of dead zones and efforts to reduce dead zone size

A
  • disappearance of fish & other marine animals -> impacting economically important waters
  • improved fertilizer use by farmers and wetland restoration in the Mississippi watershed
17
Q

1º production

A
  • amount of energy that autotrophs convert into usable chemical energy (organic compounds)
  • determines amount of energy available for consumption by:
    -> Herbivores
    -> Carnivores
    -> Detritivores
18
Q

global energy budget

A
  • 1º production driven by availability of solar energy
    ^ (approx. 1022 J of solar energy/day)
  • not all solar radiation is available for p/s…
    -> absorbed, scattered, reflected by clouds/dust, lands on non-photosynthetic surfaces
  • only 1% of visible light that strikes photosynthetic organisms is converted into chemical energy
  • photosynthetic rates / light absorption dep. on photosynthetic accessory pigments (chlorophyll, carotenoids, phycobilins)
19
Q

GPP

A

rate of conversion of light energy->chemical energy (i.e. biomass) by p/s

20
Q

NPP

A
  • rate of chemical energy (i.e. biomass) production after resp has been subtracted
  • (NPP = GPP – Respiration)
  • amount of energy available to consumers
21
Q

NEP

net ecosystem production

A

GPP - community resp

22
Q

estimating production

A

important diff between NPP & biomass of producers present at a given time (i.e. standing stock)

eg. forest standing stock > grassland standing stock but NPP of forests is typically smaller than NPP of grasslands

23
Q

1º production in diff ecosystems & geographical locations

A
  • Rainforests:
    -> high NPP
    -> large contribution to global NPP
  • Oceans:
    -> low NPP
    -> large contribution to global NPP
  • Deserts:
    -> low NPP
    -> small contribution to global NPP
  • Corals:
    -> high NPP
    -> small contribution to global NPP
24
Q

1º production in aquatic systems is limited by…

A

light & nutrients

-> light availability limits production to surface waters in freshwater & marine ecosystems

25
Q

Aquatic ecosystems

Geographic variation in 1º production is largely shaped by nutrients

A
  • iron availability in central ocean gyres
  • nitrogen limitation in marine coastal waters
  • phosphate limitation in freshwater

-> many of these patterns changed by human activity…

eg. eutrophication from domestic, industrial & agricultural activity

26
Q

terrestrial ecosystem

A
  • on large scales, 1º production driven by climate: ↑ productivity in warm & wet areas
  • on regional & local scales, production constrained by nutrient availability
    -> plants have extensive adaptations to sequester nutrients (e.g. extensive roots, interactions with fungi & bacteria)
27
Q

example of human activity/eutrophication impacting terrestrial ecosystems

A

Alpine meadows

  • many plants mutualistic with microbes to survive low nutrient availability
  • nutrient addition => switches plant-microbe interactions towards parasitism & ↓ production in some plant sp
28
Q

Gross secondary production (GSP)

A

total energy taken in - excretion (food eaten - excretion)

29
Q

Net secondary production (NSP)

A

amount of energy in consumers’ food that is converted to biomass (GSP - respiration)

30
Q

Production efficiency

A
  • calculate eff. as % of energy assimilated from food that is used for growth (i.e. new biomass)
  • NSP ÷ GSP
  • inefficiencies occur (never 100%) as not all of what organism eats can be digested & organisms use energy (i.e. energy resp)
31
Q

trophic efficiency

A

% production transferred at each trophic step

  • trophic efficiency < production efficiency (some portion of each trophic level is not consumed)
  • trophic eff. typically ~10% (range from 5-20%)
32
Q

where does all the energy go (in trophic efficiency)?

A
  • decomposers: breakdown dead organic matter externally & then absorb nutrients (e.g. bacteria, fungi, protists)
  • detritivores: eat/consume dead organic matter/detritus (e.g. earthworms, millipedes, slugs, termites)
  • coprovores: organisms that consume & re-digest waste produced by other
33
Q

Why is so much ‘food’ left uneaten?

A
  • global terrestrial NPP ~6x10¹º metric tons/ year…
  • of which herbivores consume < 20%
34
Q

the green world hypothesis

A

top-down control of herbivores by predators allows plant biomass to accumulate

35
Q

the bad tasting world hypothesis

A

plants evolve defenses that force herbivores to compete for limited amount of palatable food

-> bottom-up regulation

ecology and conservation (9 decks)

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