Lecture 19: Ecosystems: Phosphorus cycle, terrestrial nutrient regeneration

Question 1

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

Answer 1

nitrogen

Question 2

Nitrogen exists in ____________________

Answer 2

many oxidized and reduced forms

Question 3

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

Answer 3

• not a useable form for organisms
• limiting for growth

Question 4

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

Answer 4

nitrogen fixation

Question 5

Five major steps in the nitrogen cycle

Answer 5

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

Question 6

Five major steps in the nitrogen cycle - nitrogen fixation

Answer 6

Conversion of atmospheric nitrogen into forms producers can use

Question 7

five major steps in the nitrogen cycle - Nitrification

Answer 7

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).

Question 8

five major steps in the nitrogen cycle - Assimilation

Answer 8

Conversion of useable forms of nitrogen into plant/producer tissue

Question 9

five major steps in the nitrogen cycle - Mineralization

Answer 9

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

Question 10

five major steps in the nitrogen cycle - denitrification

Answer 10

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

Question 11

how is some nitrogen fixation driven by lightning strikes

Answer 11

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

Question 12

Most biotic nitrogen fixation achieved by what three groups of bacteria

Answer 12

1. Cyanobacteria
2. Azotobacter
3. Rhizobium

Question 13

what are Cyanobacteria

Answer 13

free-living autotrophs

Question 14

what are Azotobacter

Answer 14

free living soil microbe

Question 15

what are Rhizobium

Answer 15

it forms symbiotic relationships with the roots of some plants

Question 16

Which major group of plants has rhizobium?

Answer 16

legume (pea family) plants

Question 17

rhizobium on legume plants

Answer 17

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

Question 18

Phosphorus is a major component of what

Answer 18

• nucleic acids
• cell membranes
• energy transfer systems
• bones
• teeth.

Question 19

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

Answer 19

• simpler
• bound to the land and water

Question 20

_____________ result directly from ____________ of rocks.

Answer 20

• Phosphate ions
• weathering

Question 21

_______________________ phosphorus in the form of ____________________.

Answer 21

• Plants assimilate
• phosphate ions

Question 22

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

Answer 22

• Phosphate ions
• water and soil

Question 23

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

Answer 23

excreted as phosphate ions

Question 24

how is the phosphorous cycle different than the nitrogen cycle

Answer 24

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

Question 25

____________ significantly impact phosphorus availability

Answer 25

Acidity levels

Question 26

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

Answer 26

- moderately strong acidic and basic - insoluble molecules - precipitation and storage

Question 27

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

Answer 27

- reduced productivity - elevated rates of phosphorus precipitation

Question 28

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

Answer 28

doubled

Question 29

Sources of human nitrogen inputs

Answer 29

- Fertilizer production and use - Nitric oxide from fossil fuel burning - Planting nitrogen fixing crops on large scales

Question 30

Fertilizers also used extensively to __________________

Answer 30

elevate phosphorous levels

Question 31

Natural systems have ___________________________________

Answer 31

evolved under nitrogen and phosphorus limitation

Question 32

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

Answer 32

- Excess nutrients - transfer - destabilize primary production

Question 33

define Cultural eutrophication

Answer 33

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

Question 34

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

Answer 34

nitrogen and phosphorus runoff from fertilizers and detergents

Question 35

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

Answer 35

respiration of the decomposers.

Question 36

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

Answer 36

- Reduced oxygen - uninhabitable zones

Question 37

eutrophication results in __________________ with large, continuous aquatic systems.

Answer 37

aquatic “dead zones”

Question 38

explain the distribution of aquatic and marine dead zones world wide

Answer 38

- coastal - near lands with lots of people

Question 39

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

Answer 39

- healthy algae populations - rich and stable food web

Question 40

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

Answer 40

less natural land cover filtering and abnormally high nutrient inputs

Question 41

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.

Answer 41

- destabilized food web - eutrophication

Question 42

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

Answer 42

primary consumers

Question 43

result of oyster filtering

Answer 43

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

Question 44

uptake by plants & decomposition by microorganisms are sensitive to what

Answer 44

temperature, moisture, and pH

Question 45

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

Answer 45

resulting in nutrient limitations on growth.

Question 46

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

Answer 46

- Decomposition - limiting step - within terrestrial ecosystems

Question 47

Decomposition (release of nutrients) occurs via 4 processes:

Answer 47

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.

Question 48

Fungi break down components of the detritus that ________________________

Answer 48

cannot be broken down by other processes

Question 49

Saprotrophic fungi

Answer 49

The groups of fungi that are involved in detritus decomposition

Question 50

what are Fungal hyphae

Answer 50

- threadlike network of growing and feeding structures - penetrate plant and wood material bacteria cannot reach

Question 51

what is lignin

Answer 51

gives wood its key “woody” properties

Question 52

what can break down lignin

Answer 52

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

Question 53

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

Answer 53

- enzymes - absorb

Question 54

what improves nutrient uptake by terrestrial plants.

Answer 54

Mycorrhizal associations between fungi and plant roots

Question 55

two major forms of mycorrhizal

Answer 55

1. Arbuscular mycorrhizae 2. Ectomycorrhizae

Question 56

define arbuscular mycorrhizae

Answer 56

- 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.

Question 57

define ectomycorrhizae

Answer 57

- 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

Question 58

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

Answer 58

- found in all ecosystems - valuable - nutrient poor soils

Question 59

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

Answer 59

uptake of less soluble nutrients

Question 60

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

Answer 60

increasing surface area

Question 61

The _________ secreted by the mycorrhizae further improve the ______________________.

Answer 61

- enzymes - extraction of nutrients

Question 62

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

Answer 62

- prevent disease - producing antibiotics