Deck 21: Decomposition and Nutrient Cycling

Question 1

As decomposition proceeds,which molecule is lost to the atmosphere?

A)H₂O
B)CH₄
C)CO₂
D)NH₃

Answer 1

C

Question 2

Which of the following are considered decomposer mesofauna?

A)bacteria
B)earthworms
C)millipedes
D)mites

Answer 2

D

Question 3

Litter degrades into a dark brown or black homogeneous organic matter known as ________.

Answer 3

humus

Question 4

Given that mass loss is expressed as a negative exponential function (original mass remaining = e-kt),how much mass would be left after 20 weeks given a decomposition coefficient k = 0.0167 in units of proportion mass loss per week?

A)0)203
B)0)716
C)0)916
D)1)390

Question 5

Animals that feed on bacteria and fungi are called ________.

Question 6

In an estuary,the zone of maximum vertical difference in density is called a(n)________.

Question 7

The incorporation of mineral nutrients into an organic form is called ________.

Question 8

Which of the following are decomposers?

A)mushrooms
B)mites
C)millipedes
D)all of the above

Question 9

What happens to most of the nitrogen in a leaf every autumn?

A)It is resorbed by the tree.
B)It is released as N₂ gas.
C)It is broken down in soil.
D)It is consumed by decomposers.

Question 10

In a process known as the ________,the rise and fall of water depth with tidal cycles bring nutrients into coastal marshes from coastal ocean waters.

Question 11

Bacteria and fungi secrete ________ into plant and animal tissues to break down the complex organic compounds.

Question 12

Which of the following breaks down the slowest during decomposition?

A)simple sugars
B)cellulose
C)chitin
D)lignin

Question 13

The process of decomposition releases ________ to bacteria and fungi.

A)oxygen
B)energy
C)glucose
D)protein

Question 14

The release of organically bound nutrients into an inorganic form is called ________.

Question 15

When calculating leaf litter decomposition,what must be taken into account?

A)carbon uptake by leaf
B)mass added by decomposers like fungi
C)waste from earthworms
D)water reuptake by the tree

Question 16

In decomposition,fungi generally

A)extend hyphae to invade litter and excrete hypha.
B)break down litter through shredding.
C)consume microbivores on tissues.
D)gain energy directly through photosynthesis.

Question 17

________ is the process by which plants absorb a portion of their nutrients from senescing tissues to be stored and used for the production of new tissues.

Question 18

The rate of net primary productivity can be limited directly by the availability of

A)organic nutrients in the soil solution.
B)inorganic nutrients in the soil solution.
C)organic carbon in the soil solution.
D)inorganic carbon in the soil solution.

Question 19

The breakdown of chemical bonds that were formed during the construction of plant and animal tissues is called ________.

Question 20

In open water,the undissolved remains of dead organisms and other organic material that drifts toward the bottom is called ________ organic matter.

Question 21

In general,litter with a C/N ratio greater than 30 leads to immobilization,litter with a C/N ratio less than 20 leads to mineralization,and litter with a C/N ratio of 20-30 leads to a balance of immobilization and mineralization resulting in no net N production.If garlic mustard leaf litter collected on the forest floor had 43.2 percent C and 1.16 percent N,this tissue would lead to

A)immobilization.
B)mineralization.
C)a balance of immobilization and mineralization.
D)preferential consumption.

Question 22

In open-water ecosystems,decomposition occurs primarily in the

A)thermocline.
B)hypolimnion.
C)epilimnion.
D)benthic zone.

Question 23

The rate of nutrient cycling in an ecosystem

A)depends only on the rate of photosynthesis.
B)depends only on the rate of decomposition.
C)does not depend on the rate of photosynthesis or the rate of decomposition.
D)depends on both the rate of photosynthesis and the rate of decomposition.

Question 24

The microbial loop results from

A)fungal attack on litter and subsequent consumption by microbivores.
B)leaching of litter that stimulates detritivores.
C)enhanced decomposition of labile litter materials enhancing food web turnover.
D)exudate release in the rhizosphere stimulating decomposition and nutrient release.

Question 25

Coastal zones of contact between freshwater from streams and rivers and saltwater from the ocean are called

A)estuaries.
B)headwaters.
C)deltas.
D)coastal upwelling zones.

Question 26

Which of the following is a zone of decomposition?

A)forest canopy
B)photic zone
C)forest floor
D)kelp forest

Question 27

The rate of decomposition is greatest in

A)cold and moist environments.
B)cold and dry environments.
C)warm and moist environments.
D)warm and dry environments.

Question 28

Which of the following processes act to "tighten" the nutrient spiraling in streams?

A)faster flow
B)shredder invertebrates
C)collector invertebrates
D)higher stream gradient

Question 29

Why do areas with high NPP typically have a high rate of nutrient cycling?

A)High amounts of productivity increase the number of decomposers.
B)High amounts of productivity increase water production.
C)High amounts of productivity cause low net mineralization rates.
D)High amounts of productivity use low amounts of nutrients.

Question 30

Which of the following is true regarding POM?

A)It is dissolved organic matter.
B)It consists of living microorganisms.
C)It is heavier than DOM.
D)It exists only in lakes.

Question 31

The process of conversion of nutrients from an organic form into an inorganic form that plants can use is called

A)immobilization.
B)respiration.
C)transpiration.
D)mineralization.

Question 32

Aquatic arthropods that fragment organic particles and also eat bacteria and fungi on the surface of the litter are called

A)shredders.
B)filtering collectors.
C)gathering collectors.
D)grazers.

Question 33

The uptake of minerals by decomposers is referred to as

A)mineralization.
B)immobilization.
C)net mineralization rate.
D)decomposition.

Question 34

Which of the following is the slowest to decompose?

A)proteins
B)sugars
C)lignins
D)cellulose

Question 35

Which of the following variables is the coefficient that estimates decomposition rate?

A)e
B)k
C)t
D)d

Question 36

Why does the C/N ratio decline over time?

A)Mass increases over time.
B)Mass is converted into microbes over time.
C)Mass is converted into plants over time.
D)More carbon is introduced into the system.

Question 37

The C/N ratio of litter is important because litter with a

A)high C/N ratio does not contain enough nitrogen for decomposers,resulting in immobilization.
B)low C/N ratio does not contain enough nitrogen for decomposers,resulting in immobilization.
C)high C/N ratio cannot be utilized by most organisms without extra carbon available.
D)low C/N ratio cannot be utilized by most organisms without extra carbon available.

Question 38

In which season does lake stratification occur?

A)summer
B)spring
C)fall
D)winter

Question 39

How can minerals captured via immobilization be released back into the soil?

A)via microbivores
B)via fungal absorption of minerals
C)via herbivores
D)via plant reuptake

Question 40

In which of the following is the process of nutrient cycling sometimes described as nutrient spiraling?

A)streams and rivers
B)oceans
C)lakes
D)forests

Question 41

Soil organic matter contains recalcitrant compounds that are of low quality and contain little energy for decomposers.

Question 42

Most of the nutrients in the leaves of a deciduous plant are lost from the plant when the leaves senesce and drop to the ground.

Question 43

Decomposition proceeds faster in moist environments than in dry environments.

Question 44

Decomposers are primarily autotrophs.

Question 45

Litterbags can be used to estimate the rate of decomposition.

Question 46

In open-water systems such as lakes and oceans,decomposition occurs mostly in the surface layer.

Question 47

The salt marsh system is dominated by

A)carnivores.
B)herbivores.
C)secondary consumers.
D)decomposers.

Question 48

What is swidden agriculture?

A)immediate replanting of crops following harvest
B)clearing and burning a site to be replanted later
C)the use of chemical fertilizers to increase yields
D)the use of organic fertilizers to increase yields

Question 49

The rate of nutrient cycling in an ecosystem is a function of physical characteristics of the ecosystem,not biological processes such as photosynthesis and decomposition.

Question 50

Bacteria and fungi have higher C/N ratios than most of the plant litter they consume.

Question 51

Aerobic decomposition occurs at a faster rate than anaerobic decomposition.

Question 52

The physical fragmentation of organic matter into smaller pieces is achieved primarily by invertebrate detritivores.

Question 53

All heterotrophs to some degree function as decomposers.

Question 54

In oceans,how does the vertical movement of cold water affect surface organisms?

A)by bringing nutrient-rich water to the surface
B)by bringing oxygen-rich water to the surface
C)by bringing waste down to the sea floor
D)by increasing productivity via warmer temperatures

Question 55

A C/N ratio of 134:1 will usually lead to immobilization.

Question 56

In an estuary,the zone of maximum vertical difference in density of water layers is called the

A)thermocline.
B)pycnocline.
C)mixing zone.
D)hypolimnion.

Question 57

Bacteria,fungi,and animals are all important in decomposition.

Question 58

What is the Haber-Bosch process?

A)a farming technique
B)process for creating fertilizers
C)process for organic farming
D)use of burning in agriculture

Question 59

The rate of decomposition is faster for proteins,simple sugars,cellulose,and hemicellulose than it is for lignin.

Question 60

During the process of decomposition,carbon quality typically declines.

Question 61

In open-water ecosystems,turnover prevents the movement of nutrients between the bottom and surface layers.

Question 62

Estuaries receive nutrients both from tides and from streams and rivers.

Question 63

The region of the open ocean where the north and south equatorial currents meet is deficient in nutrients and supports little life.

Question 64

In salt marshes,only a small portion of primary production is consumed by herbivores.