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General Ecology > Lecture 19: Ecosystems: Phosphorus cycle, terrestrial nutrient regeneration > Flashcards

Lecture 19: Ecosystems: Phosphorus cycle, terrestrial nutrient regeneration Flashcards

1
Q

what element is essential as building blocks of amino acids, for building proteins, and DNA

A

nitrogen

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2
Q

Nitrogen exists in ____________________

A

many oxidized and reduced forms

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3
Q

Most nitrogen is found in the atmosphere (N2), which is _____________________________ — availability of usable nitrogen is often ______________

A
  • not a useable form for organisms
  • limiting for growth
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4
Q

Most useable nitrogen in biological systems originates from the process of _______________

A

nitrogen fixation

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5
Q

Five major steps in the nitrogen cycle

A
  1. Nitrogen fixation
  2. Nitrification
  3. Assimilation.
  4. Mineralization
  5. Denitrification
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6
Q

Five major steps in the nitrogen cycle - nitrogen fixation

A

Conversion of atmospheric nitrogen into forms producers can use

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7
Q

five major steps in the nitrogen cycle - Nitrification

A

The conversion by bacteria of unusable, excreted forms of organic nitrogen (ammonia) back into forms that can be used by producers (think of this as organic recycling).

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8
Q

five major steps in the nitrogen cycle - Assimilation

A

Conversion of useable forms of nitrogen into plant/producer tissue

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9
Q

five major steps in the nitrogen cycle - Mineralization

A

Breakdown of biological nitrogen into inorganic forms (e.g. ammonia)

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10
Q

five major steps in the nitrogen cycle - denitrification

A

The breakdown of organic nitrogen in the absence of oxygen, resulting in the release of molecular nitrogen back to the atmosphere

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11
Q

how is some nitrogen fixation driven by lightning strikes

A

lightning contains enough energy to convert Nitrogen gas into Nitrates that plants can use

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12
Q

Most biotic nitrogen fixation achieved by what three groups of bacteria

A
  1. Cyanobacteria
  2. Azotobacter
  3. Rhizobium
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13
Q

what are Cyanobacteria

A

free-living autotrophs

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14
Q

what are Azotobacter

A

free living soil microbe

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15
Q

what are Rhizobium

A

it forms symbiotic relationships with the roots of some plants

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16
Q

Which major group of plants has rhizobium?

A

legume (pea family) plants

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17
Q

rhizobium on legume plants

A
  • Reaction requires limited oxygen
  • Nodules provide very stable, low oxygen conditions
  • Nitrogen gas used to make ammonium compounds.
  • These compounds are absorbed by plants.
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18
Q

Phosphorus is a major component of what

A
  • nucleic acids
  • cell membranes
  • energy transfer systems
  • bones
  • teeth.
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19
Q

The phosphorus cycle is __________ than the nitrogen cycle, because phosphorus is ______________ (no gas phase) and does not readily undergo oxidation and reduction.

A
  • simpler
  • bound to the land and water
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20
Q

_____________ result directly from ____________ of rocks.

A
  • Phosphate ions
  • weathering
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21
Q

_______________________ phosphorus in the form of ____________________.

A
  • Plants assimilate
  • phosphate ions
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22
Q

_____________ are taken up from __________ and used directly in organic molecules

A
  • Phosphate ions
  • water and soil
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23
Q

Excess phosphorus in the diet of organisms is also ________________________, making it readily available again.

A

excreted as phosphate ions

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24
Q

how is the phosphorous cycle different than the nitrogen cycle

A

there are no complex transitional and unusable forms in the Phosphorus cycle

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25
Q

____________ significantly impact phosphorus availability

A

Acidity levels

26
Q

In _____________________________ conditions, phosphate ions bond tightly to other elements to form ______________ - including calcium, leading to _____________________ in aquatic systems

A
  • moderately strong acidic and basic
  • insoluble molecules
  • precipitation and storage
27
Q

The well oxygenated surface waters of aquatic systems can experience _______________________ in the warm summer months because of the ___________________________________________.

A
  • reduced productivity
  • elevated rates of phosphorus precipitation
28
Q

Human activities have approximately _______________ the amount of nitrogen going into terrestrial systems.

A

doubled

29
Q

Sources of human nitrogen inputs

A
  • Fertilizer production and use
  • Nitric oxide from fossil fuel burning
  • Planting nitrogen fixing crops on large scales
30
Q

Fertilizers also used extensively to __________________

A

elevate phosphorous levels

31
Q

Natural systems have ___________________________________

A

evolved under nitrogen and phosphorus limitation

32
Q

________________ not used by crops ________ to natural systems and ___________________________ in those systems

A
  • Excess nutrients
  • transfer
  • destabilize primary production
33
Q

define Cultural eutrophication

A

Excessive increase in productivity in an aquatic system due to human activity

34
Q

The ____________________________________ feed algae that bloom (unnatural population density) and cloud the water.

A

nitrogen and phosphorus runoff from fertilizers and detergents

35
Q

Decomposition of the dying algae from the bloom significantly reduces dissolved oxygen — ________________

A

respiration of the decomposers.

36
Q

_____________ creates ______________ with too little oxygen for multicellular marine life like fish, crabs, etc.

A
  • Reduced oxygen
  • uninhabitable zones
37
Q

eutrophication results in __________________ with large, continuous aquatic systems.

A

aquatic “dead zones”

38
Q

explain the distribution of aquatic and marine dead zones world wide

A
  • coastal
  • near lands with lots of people
39
Q

In the bay, ____________________ , fed by the naturally high nutrient levels of an estuary system, function as the primary producers for a _________________.

A
  • healthy algae populations
  • rich and stable food web
40
Q

More people upstream of the Chesapeake bay means ________________________ (fertilizers and sewage)

A

less natural land cover filtering and abnormally high nutrient inputs

41
Q

less natural land cover filtering and abnormally high nutrient inputs results in a ________________________, with over-abundant primary producers driving ______________ that heavily impacts higher trophic levels.

A
  • destabilized food web
  • eutrophication
42
Q

Oysters are critical ______________ in estuarine systems, filtering up to 50 gallons of water per day, and consuming filtered plankton and other organic particles.

A

primary consumers

43
Q

result of oyster filtering

A

positively impact water clarity (with cascading benefits), and reduce algae abundance

44
Q

uptake by plants & decomposition by microorganisms are sensitive to what

A

temperature, moisture, and pH

45
Q

Plant uptake of nutrients typically has the capacity to be faster than the regeneration rate within an ecosystem, or the inputs from outside — ________________________

A

resulting in nutrient limitations on growth.

46
Q

______________ is the ________________ in nutrient regeneration _______________________________ — the brown food web limits the green food web.

A
  • Decomposition
  • limiting step
  • within terrestrial ecosystems
47
Q

Decomposition (release of nutrients) occurs via 4 processes:

A
  1. Water leaching soluble minerals and organic compounds.
  2. Consumption by large detritivores.
  3. Breakdown of woody components by fungi.
  4. Bacteria finishing off the rest.
48
Q

Fungi break down components of the detritus that ________________________

A

cannot be broken down by other processes

49
Q

Saprotrophic fungi

A

The groups of fungi that are involved in detritus decomposition

50
Q

what are Fungal hyphae

A
  • threadlike network of growing and feeding
    structures
  • penetrate plant and wood material bacteria cannot reach
51
Q

what is lignin

A

gives wood its key “woody” properties

52
Q

what can break down lignin

A

it can only be broken down by a class of fungi known as the white rot fungi

53
Q

Fungi release __________that break down surrounding material, then they __________ the resulting sugars and amino acids.

A
  • enzymes
  • absorb
54
Q

what improves nutrient uptake by terrestrial plants.

A

Mycorrhizal associations between fungi and plant roots

55
Q

two major forms of mycorrhizal

A
  1. Arbuscular mycorrhizae
  2. Ectomycorrhizae
56
Q

define arbuscular mycorrhizae

A
  • fungi penetrate the cell walls in root tissue and form branching vessels in close contact with root cell membranes
  • common in herbaceous plants, including many crops.
57
Q

define ectomycorrhizae

A
  • Form a dense coating around the outside of small roots and penetrate the spaces between cells in the outer layer of the root
  • common in woody plants
58
Q

Mycorrhizae are _____________________, but are particularly __________ for plant uptake in systems with __________________

A
  • found in all ecosystems
  • valuable
  • nutrient poor soils
59
Q

Mycorrhizae help most in the __________________, like phosphorus - key limiting nutrient.

A

uptake of less soluble nutrients

60
Q

Mycorrhizae penetrate more soil area than the original root structure is capable of, ________________ for nutrient assimilation

A

increasing surface area

61
Q

The _________ secreted by the mycorrhizae further improve the ______________________.

A
  • enzymes
  • extraction of nutrients
62
Q

Mycorrhizae, and especially ectomycorrhizae, can help ____________ by physically excluding pathogens or _____________

A
  • prevent disease
  • producing antibiotics

General Ecology (23 decks)

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